# Headphone & Amp Impedance Questions? Find the answers here!



## proton007

Hi all,

 A lot of people ask this question in the other sections, so I thought this can be the thread to discuss it and hopefully it can act as a reference.

 Headphones come in variety of Impedance (or *Nominal* Impedance values). Some manufacturers like Beyerdynamic have 2-3 different impedances for the same model, which they list for different sources.

 So the question is, how to get the correct impedance for your source? And how to check which amp to get ?

 I'll try to explain this as far as I know, please feel free to correct me!
  
*The Hydraulic Analogy for the simple minded:*
 I think this analogy can help appreciate the need for an amplifier and establish a good basis for understanding the concepts ahead.


> A voltage source is like a water pump, it creates pressure (voltage) that passes through pipes (Load). The amount of water that passes through the pipe per second, or the flow of water, is the Current. The narrower the pipe (Higher Impedance), the more pressure (Higher Voltage) you need to maintain the same amount of water flow (Same Current).
> The reverse also applies; a wider pipe will need less pressure.
> 
> A headphone can be considered as a sprinkler. It utilizes the water given to it, and spreads it across the lawn (creates sound). We want the sprinkler to cover the lawn (get to a comfortable volume), too much and it'll wet the house, too little and its not enough.
> ...


 
  

*First of all, facts to establish before we go ahead:*

A perfect/ideal Amp will produce a fixed voltage at a particular gain/volume setting, here we refer to it as Vsource (or _Vs_) .
Voltages in terms of AC always use 'Vrms' to denote the mean voltage. Hence, Vload and Vsource are Vrms values.
The gain used by amps is just a multiplier. It tells you how much is the original signal multiplied by. So for any gain G, Vout = G*Vin
Amps have their own internal Impedance when seen from the output side, we call this 'source impedance' or '_Zs_'.
A headphone will act as the load for this system, its 'load impedance' is '_Zl_'. The voltage across this load is represented as '_Vl_'.
Headphones impedance as specified by manufacturer is only *nominal* impedance, but actually,it varies with the frequency of the signal. Some headphones can have as much as double this value at certain frequencies. We call this value 'load impedance' , or 'Zl'4) All headphones have a sensitivity rating, given in dB (Decibels) SPL/mW @ 500 Hz or 1kHz. For dB (Decibels) take a look at the links below. This denotes the "Sound Pressure Level" created by the diaphragm on 1mW power @ 500 or 1kHz signal. There is a rough relation between the SPL and loudness experienced by our ears (For more information: Loudness & Decibels). Note that some manufacturers reference the SPL to 1 Vrms instead of 1 mW, which makes the number look better.
  
  
 Here's an impedance curve of a fairly popular headphone (HD650):
  

  
_Impedance vs Frequency_: The vertical line is the maximum impedance, while the horizontal line is the 'nominal' impedance.
  
  
 Electrically, a source and load circuit can be represented by this diagram (taken from wikipedia):

  
 As mentioned before, _Vs_ is the voltage produced by the amp, which is dissipated over its own impedance to the output (_Zs_) and the load impedance (i.e. the headphone, _Zl_). Zl and Zs are connected in series.
 The effective voltage across the headphone is _Vl_.
  
  
*Formulas:*
  

Ohms Law: Vrms = Irms * Zl
Average Power, or Pavg = (Vrms)^2 / Zl.  Alternatively, Pavg = Irms * Vrms
Vl = Vs * (Zl / (Zl + Zs)). Therefore, as Zs becomes smaller, the ratio Zl/(Zl + Zs) approaches 1.
Total Impedance of two impedances connected in Series = Z1 + Z2
Total Impedance of two impedances connected in Parallel = (Z1 * Z2)/( Z1 + Z2)
 
*From these formulas, we can make some deductions:*
  

For the same Vrms to be produced, halving the Impedance doubles Pavg, and doubling the impedance halves Pavg. Hence, Pavg is inversely proportional to Zl (from point 2 above).
If Pavg is increased, for the same Vrms, Irms needs to increase (from point 2 above).
In order for Vl to be nearly the same as Vs, Zs needs to be much smaller than Zl, or Zs<<Zl (from point 3 above).
This concept is known as Impedance Bridging, and it maximizes the efficiency of power delivered to the load. The point is to have all the Pavg delivered across the load. This can be achieved if most of the source's voltage is dissipated across the load. (Note, its efficiency of power delivery, not power efficiency itself!).
Parallel connections reduces the overall impedance, and series adds them up.
 
 Now, if you look at Amp specs you'll see the power specified at a certain min. and max. load impedance. For example, Fiio E9 has 1W (16Ω Loaded), 80mW（600Ω Loaded).

*So Average Power goes up with lower Load Impedance for the same Vrms. Is there a limit to an amp's power? *

 Yes, all amps have a power limit, which means there's a Voltage and Current limit for every amp. The limit depends on the amp's design and power requirements. At the lowest impedance, the amp can run out of current to supply to the speaker. Generally, even before the limit is reached, there will be considerable increase in THD (Total Harmonic Distortion). Anything >1% is considered unacceptable by industry standards.
 If the impedance is too high, a lot of voltage is needed to produce the desired power. This will cause amps to 'clip' once it hits the voltage limit.

*High or Low load Impedance?*:

 Connecting a lot of high impedances in parallel will reduce the impedance. For instance, two 16 Ohms connected in parallel make up 8 Ohms, while two 600 Ohms make up 300 Ohms.
 In relative terms the impedance is reduced by a factor of half in both the cases, but in absolute terms, by Ohms Law, for the same Vrms across both impedances the current requirements for 300 Ohms are easier than 8 Ohms (less by a factor of ~40). 
  
 Hence studio monitoring equipment has very high (>=600) Ohms impedance, so multiple headphones can be used without overloading the system. They can all be plugged in parallel.
  
 Consider this as a rule of thumb, in order to achieve a certain power, for the headphone to be loud enough:
  

A very high impedance causes the amp to reach its voltage limit before enough power can be delivered. There'll be clipping.
  

A very low impedance causes the amp to reach its current limit before enough power can be delivered. There'll be distortion.
 
 Hence, all amps will list the max and min impedance they can handle.

*Damping factor:*

 Resonance is another issue concerning speakers, and too much of it can cause distortion. Since the speaker basically consists of a coil moving back and forth in an magnetic field, it will generate a back EMF, or back current by Faraday's Law. This induced current will restrict the coil movement, making it slower or less responsive.

 Now looking from the speaker side, if the speaker generates a voltage, the amp is the load. If the load has lower resistance it'll allow more current to pass through, hence the back emf can be dissipated easily, controlling the unwanted oscillation at resonant frequency. This is known as a 'High Damping Factor'.

 Most speakers have this happening near the lower frequency regions, so a High Damping means the Amp can control the speaker movement tightly.

 But beware of damping marketing ploys. If amps have near zero output impedance, Damping is no longer a problem.

*In general, This means that high impedance headphones are better, right?*
_Then why do we recommend low impedance headphones for portable use?_

 The answer is because portable sources, specifically batteries, are severely limited by the Vrms they can supply, and it is typically much less than the voltage that can be produced by an amp. A high impedance headphone will not sound loud enough because it needs higher Vrms.

 Since there is a relationship between Power and SPL, the only way to increase power for portable devices is to increase current which is easier to do with lower impedances.

 This also means that high impedance headphone will theoretically make your iPod battery last longer because it'll consume less current,  but it won't be as loud as the earbuds.

 Conversely, because low impedance headphones work at lower voltages, attaching this headphone to an improperly matched Amp can overdrive the headphone with high voltage, causing damage to the diaphragm. Not that much of an issue with headphone amps unless there's a design flaw, but if you plug in your headphones in the wrong output jack, this can happen.

*How do I know if I need an Amp? Will it be suitable for my headphones ? *

 Generally, low impedance headphones are made for portable use, so an amp may not be required. But some people consider there are sonic benefits, so there's nothing against using one. Just use this to check:

 To find out if the amp fits your requirements, I'll suggest to take a look at these key points:

SPL / mW from your headphone manufacturer + the max impedance if possible(not nominal).
  

Power specs from your amp manufacturer at different impedances.
If possible, a graph of how the headphone impedance varies with the signal frequency. Some headphones can have wild variations here.
 
Use this formula to calculate the power needed:
  

Power = Antilog ( (Desired SPL - SPL per mW)/ 10).
Note that a 3dB increase in SPL will cause a 2x increase in Power. For reference, 85 dB is considered to be the limit where long term exposure can cause hearing damage.
Use 85dB to calculate the average power needed. Peaks in the music may be higher, as high as 110dB.
 
 If your amp can supply this power, and the headphone impedance falls within the mum/Max load impedance the amp can drive, then go ahead and enjoy your amp.

 Also, note that some headphones have higher impedance spikes than others (impedance variation with frequency, remember) as well and then you have the music itself where when certain dynamic passages will require higher transient peaks (higher voltage) here or there once in awhile requesting for more power. Hence its better not to push amps to their limit ( driving 600 Ohms with a portable amp may work, but it can also overload the amp due to its sensitivity and impedance characteristics).

How headphone impedance (vs frequency) affects sound.

 In case of MP3 players, where output power is not specified, you can assume that the provided earbuds are already matched. Set the volume to a comfortable level, and now plug in your new headphones. If the volume sounds similar, your headphones are adequately powered.


*I've heard about using line out. What is that?*

 A line out is a (supposedly) standardized form of signal when connecting audio devices, such that the internal amplifier of the device is bypassed. It stays at a Nominal Level, with Professional equipment at -4dBu and Consumer equipment fixed by some at -10dBu (not standard).

 It can be useful in cases when you just want to send the signal over to another device for further processing/amplification, or record the signal.

 It is always at a contstant Vrms (regardless of volume control), with the Source Impedance being somewhere around 100-200 Ohms( varies based on implementation). 

 There are two implications:
  

You cannot use it to drive speakers/headphones directly (read: without an amp). There's impedance mismatch ( source is much higher than load ),meaning most of the voltage drops at the source, with an overall high current flow in the circuit dictated by the source. Not good!
  

No volume control.
 
 While its a common feature in receivers and sound cards, its not so common in media players. The iPod supports it through the dock or aftermarket line out cables.
  
  
*Ok, now I have an amp. Where do I control the volume (source or amp)? And what levels to keep?*
  
 Most will suggest to keep the source at 100%, and use the amp for volume control. There's nothing wrong in that. But my suggestion is to adjust the source such that there is a bit of travel in the amp's volume control. It makes the control more intuitive, and allows for different headphones to be used. So, a 1 should sound like one (soft) and a 10 should be loud, with the comfortable level somewhere around 5-6.
 You don't want to have ear blasting volume at just 5, its dangerous for someone caught unaware.
 For amps with adjustable gain, you can factor in the gain as well.

Finally, to keep it simple, plug it in, take a listen and if you like what you hear then that's awesome. Enjoy the music!
  

_A few notes for those who want to dig deeper_:
  

Electrical:
  

Impedance is a complex (number) load, Z = R + jX, where R is 'resistance' and X is 'reactance', both of them represented in Ohms. This can also be written as Magnitude,|Z| and Phase θ.
  

|Z| determines the voltage/current ratio, and θ determines the phase difference between voltage and current. Hence, the Power = VI statement does not hold at all points because of the phase difference. AC Power
  

This means the headphone/speaker impedance curve will vary the power drawn by the headphone/speaker. The Real Power draw may be different from the Apparent Power draw. ( see AC Power above).
  

Line out is not standardized. Pro and consumer gear targets different references and consumer gear has a tendency to be all over the place beyond that. Some line drivers can actually run some headphones, some cannot. There's no solid rule of thumb here (and it is not load invariant).
 
Music Dynamic Range:
  

Determines the difference between the highest and lowest levels of the signal. Older Classical recordings can have a very high dynamic range (40 dB sometimes), so the average and peak power requirements of your amp will be vastly different. Modern/commercial music has a dynamic range of 2-3 dB (Loudness War), hence the average power requirements of the amp will be high.
 
Sound Characteristics of the Amp:

 "What you will hear" depends on the relationship between Zout and Zload and what the amplifier can actually do. If the amplifier can drive lots of volts into the load but has Zout (e.g. a receiver or otherwise "large" amplifier, you could probably even count some amplifiers like the Beyerdynamic A1 in here since Zout is around 100ohms) it will likely just mean attenuation or boost at various frequencies, if the amplifier cannot (e.g. "line out" on a soundcard), it will probably just mean roll-off. The former is perfectly okay, the latter is not (the former means "coloration" or whatever else you like; the later is just things not behaving).
  

Look at your amplifier's manual and find the sensitivity value for the input you are using. The value it gives is the input voltage required in order to produce maximum rated power when the volume control is set to maximum. If the input signal you are feeding to the amplifier is greater than the sensitivity value, then maximum output power will be produced before full volume on the control. Hence your amp will max out even before the dial is set to full.
  

More Links for information and concepts:
  
  
  
  

Is Sound an Illusion? - An interesting discussion about our perception of sound
 
Clipping Behaviour - One of the lesser known effects of amplifier clipping, and the damage it can do.
  

Impedance - What does it really mean?  A general discussion on impedance, damping, etc.
  

Phase Angle Vs. Transistor Dissipation - A simplified approach to understanding Safe Operating Area
  

Valves & Amplifiers - Information about valves, myths, etc.
  

The Truth About Cables, Interconnects and Audio in General (MUST READ)
  

More Truth About Cables
  

Cable Impedance - Characteristic impedance, high capacitance designs and amp stability
  

Compression In Audio - Ever wondered why some music sounds flat and lifeless, even though it's loud?
 
dB: What is a decibel?
  

Amplifier Sensitivity, Decibels, and You!
  

Impedance Matching and Bridging, and how it affects your sound.
  

Headphone Tips and Tricks
  

Noise - Auditory Effects
  

Pimp your sound card! How to get more bass under a heavy headphone load
 
More links on Damping:

 http://sound.westhost.com/impedanc.htm

 http://sound.westhost.com/project56.htm

 http://sound.westhost.com/project70.htm

 http://sound.westhost.com/z-effects.htm


Thanks to:

 obobskivich, for his notes, corrections, and links.

 stv014, for useful comments.

 RexAeterna, for useful comments.


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## firev1

I stand here give the another perspective. I feel that not all studios prefers high impedance headphones, I have seen many many studios(by videos, pictures) use relatively low impedance phones and some mastering engineers also use low impedance Denons DX000 series for their work(with good results I may add), though I concede to the fact that this may not apply to every studio. Examples of such headphones are Fostex T20rp which I have seen used in a few pop studio environments, MDR-CD900st is extremely popular in Japanese studios, D2000 once by a mastering engineer(take a look at positive feedback), the Shure 840s and DT770PRO80OHM are very popular in my school's(polytechnic) diploma courses in music. 
   
  Another point I would like to address is the use of low impedance headphones in portable audio. Although generally indeed low impedance seems to be preferred in portable audio, that is also because manufacturers have no way to address the problem of getting high sensitivity AND high impedance at the same time IMO. With high sensitivity and impedance, headphones can be driven nicely without problems associated with low damping factor(overall higher noise/distortion and frequency response screwups).
   
  As for another reason why beyerdynamic has so many different models for the same headphone, I believe it is done to balance the drive ability with amp impedance issues(generally a studio engineer may want a 600ohm, while maybe someone working on field may want a 250ohm/pro 80ohm) the benefits of course with 600ohm is more control of the driver due to increased damping factor thus lower distortion. 
   
  All that I said has been said before many many times already but I hope I'm adding meat and not rubbish in this discussion.


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## proton007

Quote: 





firev1 said:


> I stand here give the another perspective. I feel that not all studios prefers high impedance headphones, I have seen many many studios(by videos, pictures) use relatively low impedance phones and some mastering engineers also use low impedance Denons DX000 series for their work(with good results I may add), though I concede to the fact that this may not apply to every studio. Examples of such headphones are Fostex T20rp which I have seen used in a few pop studio environments, MDR-CD900st is extremely popular in Japanese studios, D2000 once by a mastering engineer(take a look at positive feedback), the Shure 840s and DT770PRO80OHM are very popular in my school's(polytechnic) diploma courses in music.


 
   
  Well, there's no official rule against this, and low impedance can certainly be used, but the effect will be seen if multiple headphones are connected in parallel.
  I hope we can get someone who works in studios to give an input on this. 
   
  Quote: 





firev1 said:


> Another point I would like to address is the use of low impedance headphones in portable audio. Although generally indeed low impedance seems to be preferred in portable audio, that is also because manufacturers have no way to address the problem of getting high sensitivity AND high impedance at the same time IMO. With high sensitivity and impedance, headphones can be driven nicely without problems associated with low damping factor(overall higher noise/distortion and frequency response screwups).
> 
> As for another reason why beyerdynamic has so many different models for the same headphone, I believe it is done to balance the drive ability with amp impedance issues(generally a studio engineer may want a 600ohm, while maybe someone working on field may want a 250ohm/pro 80ohm) the benefits of course with 600ohm is more control of the driver due to increased damping factor thus lower distortion.


 
   
  AFAIK, there's no correlation between the impedance and sensitivity. For example the Beyerdynamic models have the same sensitivity for different impedances. I feel its determined by the speaker design. Maybe someone can input on this.
  Thanks for raising the damping issue. I've added it in the main section.


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## firev1

Quote: 





proton007 said:


> AFAIK, there's no correlation between the impedance and sensitivity. For example the Beyerdynamic models have the same sensitivity for different impedances. I feel its determined by the speaker design. Maybe someone can input on this.
> Thanks for raising the damping issue. I've added it in the main section.


 
   
  Indeed, there is no correlation between impedance and sensitivity. But in portable audio, if a phone can have both high impedance and sensitivity, it will not suffer from damping factor based distortions while being very easy to drive from say a regular mobile which some models have relatively high output impedances.


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## stv014

Regarding sensitivity, some manufacturers (Sennheiser in particular) reference the SPL to 1 Vrms instead of 1 mW, which makes the number look better. Sometimes no reference level is mentioned at all, making the spec useless. The sensitivity may also be significantly worse (or less commonly better) than advertised.


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## proton007

Thanks for the practical info!
	

	
	
		
		

		
			




  Added to the thread.


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## BrownBear

Hey! I like this thread, very informative. Thanks very much.


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## proton007

Quote: 





brownbear said:


> Hey! I like this thread, very informative. Thanks very much.


 
   
  No Problem. Glad to know you like it.


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## doublea71

This is a bit hard for me to follow, not having any background in recording or any science for that matter...merely trying to match a phone with the Cowon J3...I want to get a custom IEM for the J3, but I want to make sure the J3 can handle it.


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## proton007

Quote: 





doublea71 said:


> This is a bit hard for me to follow, not having any background in recording or any science for that matter...merely trying to match a phone with the Cowon J3...I want to get a custom IEM for the J3, but I want to make sure the J3 can handle it.


 
   
  Its ok.
  Use the Cowon's own earphone impedance as a guide. Just don't go for too high an impedance, try to keep it < 64 Ohms if not using any amp.


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## doublea71

Quote: 





proton007 said:


> Its ok.
> Use the Cowon's own earphone impedance as a guide. Just don't go for too high an impedance, try to keep it < 64 Ohms if not using any amp.


 
  So the player's output impedance should be less than the earphone's impedance...is there an ideal ratio between the two?


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## RexAeterna

doublea71 said:


> So the player's output impedance should be less than the earphone's impedance...is there an ideal ratio between the two?




1/8 rule they usually go by. so say nominal impedance of a headphone is 600ohms nominal, so the ideal output impedance should be 75ohms or less. like for example, speaker amps always went by atleast the 1/8 rule. that's why well built amps had no resistance at the speaker outs(0hm output impedance) which makes them perfect voltage sources for reactive loads like speakers.


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## proton007

Quote: 





rexaeterna said:


> 1/8 rule they usually go by. so say nominal impedance of a headphone is 600ohms nominal, so the ideal output impedance should be 75ohms or less. like for example, speaker amps always went by atleast the 1/8 rule. that's why well built amps had no resistance at the speaker outs(0hm output impedance) which makes them perfect voltage sources for reactive loads like speakers.


 
   
  +1.
  But you'll seldom find media player companies telling you their output impedance, thats why I said take the stock earphones as reference, a good design means that the output impedance should be < 1/8th the earphone impedance. Hence anything around the earphone impedance should be fine. I just take the upper limit to be ~64 because it gets harder to get loud with too high impedance.


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## doublea71

Quote: 





proton007 said:


> +1.
> But you'll seldom find media player companies telling you their output impedance, thats why I said take the stock earphones as reference, a good design means that the output impedance should be < 1/8th the earphone impedance. Hence anything around the earphone impedance should be fine. I just take the upper limit to be ~64 because it gets harder to get loud with too high impedance.


 

 Maybe this is a better question for my pea-brain to ask:  What is the highest impedance IEM you could use with a J3 and still expect good results? I'm using GR07s at 50 ohms with an ipod 5.5 and it does a good job. I know the J3 is more powerful, but I'm not sure how this affects synergy with the GR07s or custom IEMs which tend to be low impedance.


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## proton007

If the Cowon is more powerful, it should play well with low impedance.
  Higher side I'd say max 64.


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## BrownBear

Quote:  





> I'm using GR07s at 50 ohms with an ipod 5.5 and it does a good job


 
  Yeah, and actually I use my Pro/4AA at 250 ohms with my 5.5G iPod with good results as well. The iPod has a decent little amp in it, for the most part.


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## stv014

Quote: 





proton007 said:


> If the Cowon is more powerful, it should play well with low impedance.
> Higher side I'd say max 64.


 
   
  Impedance alone is not a reliable indicator of how hard a headphone is to drive. For portable use, check the "Volts RMS required to reach 90 dB SPL" spec at InnerFidelity, you generally want it to be less than 0.1 Vrms. With similar values, the higher impedance headphone has the advantage, since most sources can output higher voltage to a higher impedance load, and it also reduces battery usage.


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## proton007

Quote: 





stv014 said:


> Impedance alone is not a reliable indicator of how hard a headphone is to drive. For portable use, check the "Volts RMS required to reach 90 dB SPL" spec at InnerFidelity, you generally want it to be less than 0.1 Vrms. With similar values, the higher impedance headphone has the advantage, since most sources can output higher voltage to a higher impedance load, and it also reduces battery usage.


 
   
  Thats what my main post is about, I already referred doublea71 to that but he wanted a more general solution.


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## doublea71

oy vey I still can't make heads or tails of this.


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## firev1

Quote: 





doublea71 said:


> Maybe this is a better question for my pea-brain to ask:  What is the highest impedance IEM you could use with a J3 and still expect good results? I'm using GR07s at 50 ohms with an ipod 5.5 and it does a good job. I know the J3 is more powerful, but I'm not sure how this affects synergy with the GR07s or custom IEMs which tend to be low impedance.


 
  It should do alright with all custom IEMS in the market(is there any below 16 ohms?). As for your question, impedance matters not, it is the sensitivity or the IEM that counts. That being said, I don't know the max output power of the J3 but it should drive all IEMs in the market fine(with the potential exception of ER-4S) .


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## doublea71

I think the headphone out is 29 whatevers (Ohms?) per channel (L+R).


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## Chris J

A typical headphone used in recording studios is the AKG K240 series. This is a 55 ohm headphone.

A friend of mine used several in his recording studio.
He drove them with a Bryston 2B power amp.


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## proton007

IEMs are made with portable sources in mind. Just use any IEM, it'll work perfectly fine with your J3.


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## RexAeterna

stv014 said:


> Impedance alone is not a reliable indicator of how hard a headphone is to drive. For portable use, check the "Volts RMS required to reach 90 dB SPL" spec at InnerFidelity, you generally want it to be less than 0.1 Vrms. With similar values, the higher impedance headphone has the advantage, since most sources can output higher voltage to a higher impedance load, and it also reduces battery usage.




depends. i haven't found a portable device yet that can drive my 600ohm 240DF's well. then you also have impedance vs. frequency and what most people never mention is the need for reserve power for transients and dynamics. might get reasonable and comfortable enough in volume but there is still more to it. higher impedance headphones is only better for portable use cause of damping factor/output impedance(and like mentioned, to save battery life). that's why lot people mention even with low volume and restraint dynamics it still sounds clear and nice.

i bypass all these limitations by using my headphones directly off of speaker outputs of my favorite and main power amps(limitless reserve of voltage/current, high damping factor/low output impedance close to 0/at 0ohms,ect.) and always have good results with all headphones i tried(even run my balanced Sony SA5000 off the speaker outs even though they are sensitive headphone. not problem though since i really don't have gain issues with my main amps and i listen what i consider normal volumes where i still can hear myself talk).


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## proton007

Quote: 





rexaeterna said:


> depends. i haven't found a portable device yet that can drive my 600ohm 240DF's well. then you also have impedance vs. frequency and what most people never mention is the need for reserve power for transients and dynamics. might get reasonable and comfortable enough in volume but there is still more to it. higher impedance headphones is only better for portable use cause of damping factor/output impedance(and like mentioned, to save battery life). that's why lot people mention even with low volume and restraint dynamics it still sounds clear and nice.
> i bypass all these limitations by using my headphones directly off of speaker outputs of my favorite and main power amps(limitless reserve of voltage/current, high damping factor/low output impedance close to 0/at 0ohms,ect.) and always have good results with all headphones i tried(even run my balanced Sony SA5000 off the speaker outs even though they are sensitive headphone. not problem though since i really don't have gain issues with my main amps and i listen what i consider normal volumes where i still can hear myself talk).


 
   
  600 Ohms is pretty much the upper limit when it comes to portable amps.
  But if an amp can drive such a headphone to pretty comfortable volume, then I think there isn't much improvement to be had unless you're already reaching close to the amp's limits.
  And yes, a power amp will obviously have a lot more power than the headphone needs, but can also damage your headphones due to high Vrms if pushed too high.
  Thanks for the insight


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## RexAeterna

true. also depends on sensitivity. my DF's are 88db@1v@1khz(600ohms nominal@1khz). i think limit for portable players(not amps) is 1v max which for sensitive 600ohm headphone will get volume very reasonable and possibly loud enough to be enjoyable very much. i just said it depends really is all i meant. some headphones have higher spikes than others as well and then you got the music itself where when certain dynamic passages will require higher transient peaks here or there once in awhile requesting for more power. bit too complicated. so to keep it simple. plug it in, take a listen and if you like what you hear then that's awesome. enjoy the music. that's what it's all about.


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## proton007

Quote: 





rexaeterna said:


> some headphones have higher spikes than others as well and then you got the music itself where when certain dynamic passages will require higher transient peaks here or there once in awhile requesting for more power





> so to keep it simple. plug it in, take a listen and if you like what you hear then that's awesome. enjoy the music. that's what it's all about.


 
  I'm putting this in the main post.


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## doublea71

I've given up on trying to do the math to achieve perfect synergy btw the dap and iems - it's a task way above my payscale.


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## Chris J

Quote: 





doublea71 said:


> I've given up on trying to do the math to achieve perfect synergy btw the dap and iems - it's a task way above my payscale.


 
   
  Don't forget all that information is Highly Classified!


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## obobskivich

Great guide, a few notes though:

- Impedance is Z, Resistance is R; they are different things. Source impedance is therefore Zout or Zsource. 

- The damping factor section is largely marketing fluffies; for a variety of reasons including cable resistance, and the reactivity of loads (it will inherently vary with frequency). See here for more: http://www.butleraudio.com/damping1.php

- Not all amplifiers decrease their output as Z increases; some are invariant (or nearly invariant) - the WA6 is a good example (it uses a transformer to accomplish this feat).

- The actual power needs are dictated by sensitivity, as you note, but perhaps explain the log relationship between power and output. See here for more: http://trace.wisc.edu/docs/2004-About-dB/ Basically consider peaks and the dynamic nature of music instead of static demands; the easy way to do this is to figure out how dynamic the material you want to listen to really is, and then assume that is "top end" static demand and reference that to whatever output SPL you want. I think most people probably will target 60-70 dB but maybe I'm just weird like that (I get the sense I listen at VERY low levels compared to most people, based on the lengths I go to to reduce gain; perhaps I just have super efficient cans, I don't know). So if you're listening to modern pop, you probably only need 2-3 dB of DR, and that makes your continuous power requirements relatively high. If you're listening to old classical recordings, you might see 40 dB or more of DR (the highest I've ever documented is right around 40 dB, but I don't listen to much "very old" music and I hate doing vinyl restoration) - your continuous power requirements are very low, but the peak demands are going to be substantial. Especially if you want the continuous/base-line level at a "loud ish" point (like 70 dB). 

- Line out is not standardized. Pro and consumer gear targets different references (http://www.gearslutz.com/board/so-much-gear-so-little-time/403493-4dbu-versus-10dbu.html), and consumer gear has a tendency to be all over the place beyond that (I've seen fs spec'd anywhere between 1V and 5V). Some line drivers can actually run some headphones, some cannot. I've never seen a solid rule of thumb here (and it is not load invariant). 

Also in terms of "what you will hear" - it depends on the relationship between Zout and Zload and what the amplifier can actually do. If the amplifier can drive lots of volts into the load but has Zout (e.g. a receiver or otherwise "large" amplifier, you could probably even count some amplifiers like the Beyerdynamic A1 in here since Zout is around 100ohms) it will likely just mean attenuation or boost at various frequencies, if the amplifier cannot (e.g. "line out" on a soundcard), it will probably just mean roll-off. The former is perfectly okay, the later is not (the former means "coloration" or whatever else you like; the later is just things not behaving). 

Overall I think this is a great guide!  And I agree with the "plug it in and listen" as well - just because you have something with high Zout doesn't mean it has to sound bad. I actually liked my HD 580s out of a receiver with 470ohm Zout more than any other amplifier I tried them on; it added "body" to the bottom end. So that's a preference. Of course there are also headphones with Zobels (or otherwise flat impedance curves), and that are very sensitive, that absolutely ignore this entire problem and sound the same out of anything (higher Zout just makes them quieter); they're relatively rare ime though (I can think of three Sony models, Grados, and Denons).


----------



## proton007

Hey! Thanks for the notes. 
	

	
	
		
		

		
			




  I didn't put it in initially because I wasn't sure about the technical level, it gets complex pretty fast for beginners, but I guess I'll just put it in.


----------



## obobskivich

proton007 said:


> Hey! Thanks for the notes.
> I didn't put it in initially because I wasn't sure about what technical level to follow, but I guess I'll just put it in.




I think you did a great job keeping it from being just a huge throw-up of math, and explaining things in a clear manner. Just saw a few "typo-esque" things was all (like Z over R). 

If you want some links to include, lmk, I've got a few more.


----------



## proton007

Hey, thanks for the help.
	

	
	
		
		

		
		
	


	



  Please send me any links you think will be useful, I'd be glad to add them in. I've added a few of the (simpler) links you referred me to earlier.


----------



## doublea71

I'll keep my eyes peeled for the "Headphone/Amp Impedance Matching For Dummies" on Amazon - I think I need this to be explained to me like a 6 year old....


----------



## firev1

Quote: 





obobskivich said:


> Great guide, a few notes though:
> - Impedance is Z, Resistance is R; they are different things. Source impedance is therefore Zout or Zsource.
> - The damping factor section is largely marketing fluffies; for a variety of reasons including cable resistance, and the reactivity of loads (it will inherently vary with frequency). See here for more: http://www.butleraudio.com/damping1.php


 
  I partially disagree with you, that damping factor is marketing fluff, Benchmark has proven that damping factor does make a big difference in audio in terms of distortion test(with results on AP), which has been verified by a non-commercial third party. Anyway's, its notable that your source is yet another commercial tube amp seller, though the math is correct, explanation is missing something .
   
  For the cable resistance argument, I say that for speakers and headphones, its a totally different ball game. I refer to "Audio Engineering Explained", on speakers, AC transformers in the loudspeaker wipe out the damping factor's effects on loudspeaker resonance.
   
  This is however, notably untrue in the case of headphones as they do not have space to fit in transformers, which brings DF back into the headphone ball game. Damping factor's effects while subtle in some headphones(notably D2000) can be extremely audible in the case of Balanced armatures, for me it was the X10s and Shure 840s driven to the same volume from the ipod as compared to headphone jack out to the O2 before comparisons.
   
   
  For anyone saying I'm such a "0 ohm" proponent, I do like to drive my headphones out from my receiver from time to time but I will stick with my O2 for resolution on the bass.
   
  References,
http://www.benchmarkmedia.com/discuss/feedback/newsletter/2011/12/2/0-ohm-headphone-amplifier-sonic-advantages-low-impedance-headphone-amp
  nwavguy's article on headphone impedance
  Audio Engineering Explained for professional recording pg. 199
  Sighted and single blind tests by my ears which are highly subjective


----------



## maverickronin

I think the "marketing fluff" part is how it used to be said they you needed a super low output impedance for a super high damping factor.  There's a point of diminishing returns in there somewhere.


----------



## stv014

Quote: 





maverickronin said:


> I think the "marketing fluff" part is how it used to be said they you needed a super low output impedance for a super high damping factor.  There's a point of diminishing returns in there somewhere.


 
   
  Indeed, the Benchmark article claims 100 times or higher increases in distortion compared to a (near) zero output impedance, but it ignores that the distortion of the headphone itself at a given frequency and SPL is even much higher than what is measured at the high impedance output. It shows 0.1% distortion for the HD650 with a damping factor of ~10 at 50 Hz and 106 dB SPL, but InnerFidelity measured more than 1% at the same frequency and only 100 dB SPL. "0.5 dB improvement" in distortion is obviously less impressive


----------



## firev1

Going by the article posted by obobskivich that does not seem the case. I just pointed out the difference in the working of headphones vs speakers. To add on, for the cable argument, damping factor change maybe too low in the case of headphones(impedances are not single digit like speakers)( maybe not so for IEMs eg. XBA-4/3) and maybe accounted for in tuning of the headphones.
   
  Recabling it with exotic cables with their greater lengths from multiple twist, will increase resistance and off course, may be the factor accounting for a sonic change in headphones with cables by destroying the damping factor.(my add on, I may be kidding  you).
   
  EDIT: Since measurements are taken at the headphone's inputs, acoustic outputs may be dramatically(maybe not night and day but still) affected by the electrical input? 0.5 db is the calculated distortion acoustic output I assume? 
   
  @stv014 art lies at the last 0.1% in audio they always say! , especially at >$1000


----------



## maverickronin

The issue with BAs is more their wild impedance swings which can cause pretty big FR changes.


----------



## mikeaj

firev1 said:


> EDIT: Since measurements are taken at the headphone's inputs, acoustic outputs may be dramatically(maybe not night and day but still) affected by the electrical input? 0.5 db is the calculated distortion acoustic output I assume?




If I understood it, the idea (very roughly) was to compare 1% distortion of headphones versus 1% + 0.1% distortion of headphones + amp. 10 * log10( 1.1 / 1 ) = 0.41 dB, about 0.5 dB difference. It's not a big deal in the grand scheme of things.

I think you're asking if acoustic outputs of the headphones can be dramatically changed by not-so-dramatic changes in the electrical input? Answer should be "no" probably. Let's break down the input into two components: (1) the original signal and (2) the error signal containing all the distortion products that aren't in the original. Define the input as the sum of those two components. If you've got 0.1% distortion, that means the error signal is a lot smaller than the original signal. If you had perfect headphones in some sense (0% THD, but frequency response need not necessarily be flat, etc.), the response of the headphones to the input would be the sum of the response to the original plus the sum of the response to the error. So the response to the error would be much smaller than the response to the original, since the error signal has much smaller magnitude.

In practice, for real-world headphones, the response of the sum (of original + error) isn't quite the sum of the responses (to original and to error, separately), like it was in the theoretical example above. It should be mostly close though, close enough to say that small differences in electrical inputs shouldn't create very disproportionately large changes in the acoustic output.

The other question to address is whether or not the distortion of the amplifier is of a significantly different character than the distortion of the headphones. If they were of very different types, then maybe you could pick out the added distortion of the amp, even if its magnitude were smaller than the distortion of the headphones. However, the kinds of distortion added by the amplifier are mostly the same kinds of second, third, etc. harmonic and intermodulation distortion products that the headphones themselves already are producing. If the amp is producing a 2nd harmonic distortion product and the headphone producing a 2nd harmonic distortion product of the amp's (small) 2nd harmonic distortion product, this will be really really small in magnitude, below the noise floor, etc. Also, the 2nd harmonic of a 2nd harmonic is just the 4th harmonic of the original: 2 octaves above, so not a huge deal anyway. I'm not sure if this is always true, but it doesn't seem like the distortion of the amp for a good amp and the distortion of the headphones are so significantly different in character that they aren't effectively "adding" to each other. So really, it should be the larger effect of the headphones that usually dominates.


----------



## obobskivich

firev1 said:


> I partially disagree with you, that damping factor is marketing fluff, Benchmark has proven that damping factor does make a big difference in audio in terms of distortion test(with results on AP), which has been verified by a non-commercial third party. Anyway's, its notable that your source is yet another commercial tube amp seller, though the math is correct, explanation is missing something .
> 
> For the cable resistance argument, I say that for speakers and headphones, its a totally different ball game. I refer to "Audio Engineering Explained", on speakers, AC transformers in the loudspeaker wipe out the damping factor's effects on loudspeaker resonance.
> 
> ...




My source isn't a "tube amp seller" - Butler has just re-produced some old papers in HTML (I figured it'd be easier for mobile users to view); you can get them as PDFs from Roger Rusell's website (and see the original JBL Research and Harman Research tags on them as they appeared in print in the 1960s and 1970s). They're citing Toole and Augsperger; who are more or less "authorities" in this field. There's no transformers in speakers confused; impedance is just as reactive with speakers as it is with headphones (unless you have a Zobel; MDR-F1 and MDR-MA900 are the only headphones I'm aware of with one). Again, DF is just an imagination of the marketing world. It is not the same as arguing for low Zout; Zout will influence attenuation across FR based on Z.


----------



## firev1

I was looking at the 70V speaker systems as while as ESL speakers, I apologise for any mistakes I made. I always thought that DF was the one that had to do with FR changes more so than just low Zout(since line outs ain't that low impedance either) but its just about impedance swings relative to the Zout is that right?


----------



## RexAeterna

high damping factor is from low output impedance and vice versa. usually anything above 70@8ohms is cause of too much/abuse of negative feedback. also you forget not all amps mention where that damping factor was measured. most amps only measure it at 1khz. some amps do however list damping factor of multiple frequencies like 20/50hz,1khz, and 10khz or don't even list the frequency measured at all. i don't even think headamps measure like speaker amps cause they never list the damping factor at any particular load at all and just say it's at that specific output impedance and that's it.


----------



## Chris J

Quote: 





obobskivich said:


> Great guide, a few notes though:
> - Impedance is Z, Resistance is R; they are different things. Source impedance is therefore Zout or Zsource.


 
   
   
  Actually Impedance is the algebraic sum of Resistance and Inductive & Capacitive Reactance,  so they are two inter-related things.


----------



## Chris J

Quote: 





stv014 said:


> Indeed, the Benchmark article claims 100 times or higher increases in distortion compared to a (near) zero output impedance, but it ignores that the distortion of the headphone itself at a given frequency and SPL is even much higher than what is measured at the high impedance output. It shows 0.1% distortion for the HD650 with a damping factor of ~10 at 50 Hz and 106 dB SPL, but InnerFidelity measured more than 1% at the same frequency and only 100 dB SPL. "0.5 dB improvement" in distortion is obviously less impressive


 
   
  The point is that the distortion from the amp drops when the output impedance drops (assuming you have a fairly reactive headphone), you want the amp to be as clean as possible, before you feed that signal into a headphone.    The headphone will just take that distortion and distort it even more.
   
  Unless you are a distortion loving fan of SETs........................


----------



## obobskivich

firev1 said:


> I was looking at the 70V speaker systems as while as ESL speakers, I apologise for any mistakes I made. I always thought that DF was the one that had to do with FR changes more so than just low Zout(since line outs ain't that low impedance either) but its just about impedance swings relative to the Zout is that right?




DF is a marketing creation, just like PMPO (okay, not *that* bad, but you get the idea).

FR changes are the result of the relationship between Zsource and Zload - line outs are higher impedance but consider that line inputs are also higher impedance. There's still a potential for mismatch depending on what you hook up. DF is some formula to make Zsource look pretty, iirc it's Zsource/Zload (or Zload/Zsource, whatever makes the bigger number basically) - it's completely arbitrary. It's easier to market things with a "single linear variable" than complex specs; which looks better:

Amp XYZ with output impedance 1 ohm.
Amp ABC with a DF of 5000.

XYZ can actually express a "DF of 5000" into a high impedance load, and ABC might have an output impedance even higher than 1 ohm because that's a unitless number. Make sense?






chris j said:


> Actually Impedance is the algebraic sum of Resistance and Inductive & Capacitive Reactance,  so they are two inter-related things.




I meant "R" and "Z" are different.


----------



## Chris J

obobskivich said:


> DF is a marketing creation, just like PMPO (okay, not *that* bad, but you get the idea).
> FR changes are the result of the relationship between Zsource and Zload - line outs are higher impedance but consider that line inputs are also higher impedance. There's still a potential for mismatch depending on what you hook up. DF is some formula to make Zsource look pretty, iirc it's Zsource/Zload (or Zload/Zsource, whatever makes the bigger number basically) - it's completely arbitrary. It's easier to market things with a "single linear variable" than complex specs; which looks better:
> Amp XYZ with output impedance 1 ohm.
> Amp ABC with a DF of 5000.
> ...




Just because damping factor is a unitless number does not mean it is meaningless, damping factor MUST always be referenced to a load Z, if it isn't, it truly is meaningless.
But I do agree, damping factors greater than 50 or 100 are useless as they will be swamped by the cable impedance and contact resistance of the various connectors, plus whatever determental impedance may be contained inside a loudspeaker.

YOU need a Scotch, laddie!


----------



## Chris J

Quote: 





rexaeterna said:


> high damping factor is from low output impedance and vice versa. usually anything above 70@8ohms is cause of too much/abuse of negative feedback. also you forget not all amps mention where that damping factor was measured. most amps only measure it at 1khz. some amps do however list damping factor of multiple frequencies like 20/50hz,1khz, and 10khz or don't even list the frequency measured at all. i don't even think headamps measure like speaker amps cause they never list the damping factor at any particular load at all and just say it's at that specific output impedance and that's it.


 
  Rex,
  Ouch!
  That hurts!
  Too much negative feedback?
  You didn't do your homework, did you?  LOL
  Keep in mind that headphone amps like the Grado headphone amp or the O2 or the CMOY which only use Op Amps will have approx. 100 dB of feedback at low frequencies.
   
  Other than that you raise some excellent points:  whether we are talking about a headphone amp or a "speaker amp", to some degree, damping factor always varies with frequency.


----------



## RexAeterna

chris j said:


> Rex,
> Ouch!
> That hurts!
> Too much negative feedback?
> ...




well, that's why i have you here to correct me you silly goose! to learn and all that fun stuff. i'm still trying to wrap my mind around the last papers you shared with me


----------



## obobskivich

chris j said:


> Just because damping factor is a unitless number does not mean it is meaningless, damping factor MUST always be referenced to a load Z, if it isn't, it truly is meaningless.
> But I do agree, damping factors greater than 50 or 100 are useless as they will be swamped by the cable impedance and contact resistance of the various connectors, plus whatever determental impedance may be contained inside a loudspeaker.
> YOU need a Scotch, laddie!




Yeah. If manufacturers stated real values, I'd be happy. There's an entire Rane Note devoted to this rant that I'll link instead of ranting:
http://www.rane.com/note145.html



chris j said:


> Rex,
> amps like the Grado headphone amp or the O2 or the CMOY which only use Op Amps will have approx. 100 dB of feedback at low frequencies.




So basically mean you the CMOY and the O2, right? 

I would agree with your point here too - but I like Rex's thinking: just give me Zout and be done with it, I can do the math if I'm really curious. Again, mfgrs need to see the Rane Note. :angry_face:


----------



## proton007

Haha I guess the manufacturers don't really want customers to go sneaking around, do they?
  Nor do they expect the intellect of the customer to be higher than that of a trained monkey. Everything is getting dumbed down. Technology is dictating human behavior, when 20 years ago it was the user who was responsible for getting the technology to work, program your own code, games etc.
  They only care to mention the key specs most buyers know from hearsay. Stuff like PMPO, screen resolution, GHz, dual/quad etc.


----------



## obobskivich

proton007 said:


> Haha I guess the manufacturers don't really want customers to go sneaking around, do they?
> Nor do they expect the intellect of the customer to be higher than that of a trained monkey. Everything is getting dumbed down. Technology is dictating human behavior, when 20 years ago it was the user who was responsible for getting the technology to work, program your own code, games etc.
> They only care to mention the key specs most buyers know from hearsay. Stuff like PMPO, screen resolution, GHz, dual/quad etc.




Like I've said before: a nice number to slap on the box. 

They're great at inventing new ones after they turn a given buzzword into absolutely useless dribble - e.g. "High Definition" and "HD" (there's even "HD" cars now!).


----------



## Chris J

Quote: 





rexaeterna said:


> well, that's why i have you here to correct me you silly goose! to learn and all that fun stuff. i'm still trying to wrap my mind around the last papers you shared with me


 
   
  Hey!
  I'm not too comfortable with you calling me a silly goose!
  LOL!
  I think someone needs to write "Otala and Feedback for Dummies"!
  Quote: 





obobskivich said:


> Yeah. If manufacturers stated real values, I'd be happy. There's an entire Rane Note devoted to this rant that I'll link instead of ranting:
> http://www.rane.com/note145.html
> So basically mean you the CMOY and the O2, right?
> 
> ...


 
   
  NO!
  You competely misunderstand me!
  The Grado Headphone amp is completely different than the CMOY!
  The Grado sounds wwarm and organic and luxurious because it comes in a warm, organic wooden case and costs a lot.
  The CMOY sounds cold and bright because it comes in a cold metal case!
  Other than that, they are almost identical............
	

	
	
		
		

		
		
	


	



   
  I gotta agree with your "just gimme an Zout figure!" comment.
  You can crank the damping factor number skyhigh by calculating it by using a 2,00 ohm 'phone.
  You would need a big chart to keep the manufacturers honest:
  damping fact WRT  headphone impedance WRT frequency, wouldn't you?
   
  Is this what you hate about damping factor? 
   
  BTW, go ahead and rant, you not, it's what Head Fi is for!


----------



## Chris J

Quote: 





proton007 said:


> Haha I guess the manufacturers don't really want customers to go sneaking around, do they?
> Nor do they expect the intellect of the customer to be higher than that of a trained monkey. Everything is getting dumbed down. Technology is dictating human behavior, when 20 years ago it was the user who was responsible for getting the technology to work, program your own code, games etc.
> They only care to mention the key specs most buyers know from hearsay. Stuff like PMPO, screen resolution, GHz, dual/quad etc.


 
  You forgot one of my favourite ones:
  cheap cameras with crappy lenses but really high megapixel counts.
	

	
	
		
		

		
		
	


	



  I need a beer!


----------



## obobskivich

chris j said:


> Is this what you hate about damping factor?





Yup. I don't have an issue with what it tries to relate, I have an issue with how it's been bastardized. Just like those super high-end cameras with their nifty plastic lenses and 400MP stamped on the box!


----------



## Chris J

Quote: 





obobskivich said:


> Yup. I don't have an issue with what it tries to relate, I have an issue with how it's been bastardized. Just like those super high-end cameras with their nifty plastic lenses and 400MP stamped on the box!


 
   
  OK, now I can relate!
  Thanks for the clarification.


----------



## firev1

Quote: 





obobskivich said:


> DF is a marketing creation, just like PMPO (okay, not *that* bad, but you get the idea).
> FR changes are the result of the relationship between Zsource and Zload - line outs are higher impedance but consider that line inputs are also higher impedance. There's still a potential for mismatch depending on what you hook up. DF is some formula to make Zsource look pretty, iirc it's Zsource/Zload (or Zload/Zsource, whatever makes the bigger number basically) - it's completely arbitrary. It's easier to market things with a "single linear variable" than complex specs; which looks better:
> Amp XYZ with output impedance 1 ohm.
> Amp ABC with a DF of 5000.
> ...


 
  Do manufacturers really do that? I hadn't see any in particular. The only DF measurements I saw are something like DF of XXXX@ 50 ohm, which is not useless at all.  But I agree that I would rather have the output impedance straight.


----------



## Chris J

Quote: 





obobskivich said:


> Yeah. If manufacturers stated real values, I'd be happy. There's an entire Rane Note devoted to this rant that I'll link instead of ranting:
> http://www.rane.com/note145.html
> So basically mean you the CMOY and the O2, right?
> 
> ...


 
   
  Hey!
  I finally got around to reading the "Rane Rant".
  They raise more than a few very good points:
  all these specs are meaningless unless they are fully referenced.
   
  Another irritating spec:
  Output impedance:  16-600 ohms.    What is that supposed to tell us?  Another meaningless spec!


----------



## Chris J

Quote: 





obobskivich said:


> Great guide, a few notes though:
> - Not all amplifiers decrease their output as Z increases; some are invariant (or nearly invariant) - the WA6 is a good example (it uses a transformer to accomplish this feat).


 
   
  Just noticed this, but better late than never:
   
  An amp with an output transformer is only load invariant if it is equipped with a series of taps to match the various load impedances.
   
  For example, you can see this on a lot of Vacuum Tube power amps used to drive loudspeakers: there is typically a transformer tap for 4, 8 and 16 ohm loudspeakers.
  Even this type of amp will deliver half power into a 32 ohm load as it doesn't have a 32 ohm output transformer tap.
  Of course, this assumes that the load impedcance does not vary with frequency! hich it almost always does, especially in a loudspeaker system.


----------



## obobskivich

chris j said:


> An amp with an output transformer is only load invariant if it is equipped with a series of taps to match the various load impedances.




Oh yeah, but every OT hp amp I've seen has such taps routed through a rotary switch (Cayin, Woo, etc) so I figured it was safe to assume as global.


----------



## Chris J

Quote: 





obobskivich said:


> Oh yeah, but every OT hp amp I've seen has such taps routed through a rotary switch (Cayin, Woo, etc) so I figured it was safe to assume as global.


 
   
  Oh,  I didn't know all those headphone amps have rotary switches.  my turn to be...... 
	

	
	
		
		

		
		
	


	



  I seem to remember seeing a few cheaper one without taps?
  I think Little Dot makes a few without taps?   Or have I imbibed too much Sarian Brandy?


----------



## Chris J

Quote: 





doublea71 said:


> I'll keep my eyes peeled for the "Headphone/Amp Impedance Matching For Dummies" on Amazon - I think I need this to be explained to me like a 6 year old....


 
   
  Then you probably don't want to read this:  http://www.head-fi.org/a/headphone-impedance


----------



## obobskivich

chris j said:


> Oh,  I didn't know all those headphone amps have rotary switches.  my turn to be......
> I seem to remember seeing a few cheaper one without taps?
> I think Little Dot makes a few without taps?   Or have I imbibed too much Sarian Brandy?




Those are OTL models afaik; they're fairly popular from what I've seen.


----------



## proton007

Any advantages/disadvantages of OTL ? From what I know, they're mostly for high impedance headphones.


----------



## Chris J

OTLs have a high output impedance so they work better with high impedance cans.
Output impedance ranges from approx. 60 to 100 ohms, which is really dictated by the output tube used.
Since they don't have output transformers, they are cheaper than tube amps with output transformers.
And since they don't have output transformers, theoretically they would have lower distortion and a wider bandwith than transformer coupled tube amps.


----------



## obobskivich

chris j said:


> OTLs have a high output impedance so they work better with high impedance cans.
> Output impedance ranges from approx. 60 to 100 ohms, which is really dictated by the output tube used.
> Since they don't have output transformers, they are cheaper than tube amps with output transformers.
> And since they don't have output transformers, theoretically they would have lower distortion and a wider bandwith than transformer coupled tube amps.




What he said. 

From user reviews, they tend to be preferenced for higher impedance headphones (and honestly there's not a lot of high Z cans that I personally like, so I haven't ever tested this out for myself - most OTL amps are dangerous with one of my favorite cans).


----------



## Chris J

Another way to look at this is to say that it is a fairly cost effective way to get into tube amplification:
   
  A high impedance 'phone with an OTL tube amp is cheaper than a low impedance 'phone with a transformer coupled tube amp.
  Good output transformers are expensive!
   
  OTOH: a good solid state amp with drive both low and high impedance cans with ease.
  IEM guys seem to get into trouble with excessive gain and noise from poor amp matching, but that is another argument for another day.


----------



## proton007

So far the only OTL amp I've heard of is the crack OTL, but seems like its a fairly old design, when headphones were inefficient and high impedance.


----------



## T.F.O.A

Great threat, but since i don't have any science background... smokes coming out of my ears.


----------



## proton007

Quote: 





t.f.o.a said:


> Great *thread*, but since i don't have any science background... smokes coming out of my ears.


 
  FTFY.
  And thanks but I guess you do need a bit of maths/science to understand it.


----------



## obobskivich

proton007 said:


> So far the only OTL amp I've heard of is the crack OTL, but seems like its a fairly old design, when headphones were inefficient and high impedance.




As opposed to now when they're inefficient and low impedance?


----------



## proton007

Quote: 





obobskivich said:


> As opposed to know when they're inefficient and low impedance?


 
   
  Well, nowadays it seems to be more like efficient and high/low impedance...


----------



## obobskivich

proton007 said:


> Well, nowadays it seems to be more like efficient and high/low impedance...




Aside from noticing my glaring spelling error (BAH!), I was making a jab at the orthodynamic products that've come about recently.


----------



## proton007

Quote: 





obobskivich said:


> Aside from noticing my glaring spelling error (BAH!), I was making a jab at the orthodynamic products that've come about recently.


 
   
  Yeah, thats what I was thinking of, I couldn't find the word...or-tho-dy-namic


----------



## Chris J

Quote: 





obobskivich said:


> Aside from noticing my glaring spelling error (BAH!), I was making a jab at the orthodynamic products that've come about recently.


 
   
  OK, as long as you weren't taking a dig at AKG Q701!


----------



## obobskivich

chris j said:


> OK, as long as you weren't taking a dig at AKG Q701!




They aren't inefficient though, unless your point of reference is a Beats Pro or A.00 or something equally insane (you know, 120-130 dB/V - like a boss). Seriously, by pre-iPood standards they really don't stand that exotically apart, and if the original reviewers back in 2006 had tried them from home hi-fi equipment or similar (which we all "know" is evil and not designed properly for use with headphones (Because if it was, companies like Corda and Woo couldn't hawk multi-thousand dollar components to us!)) instead of their mobile devices, the entire mythos about their "hard to drive" qualities would've never started up. 

Of course, the converse problem is now that the HE-6 is out, and just as bad as the K1000 from years gone by, the 70x gets grouped in the same schema of "hard to drive" with it. So now you've got people convinced that you need a 6W headphone amplifier (which you don't need for anything), for 70x.


----------



## Chris J

Quote: 





obobskivich said:


> They aren't inefficient though, unless your point of reference is a Beats Pro or A.00 or something equally insane (you know, 120-130 dB/V - like a boss). Seriously, by pre-iPood standards they really don't stand that exotically apart, and if the original reviewers back in 2006 had tried them from home hi-fi equipment or similar (which we all "know" is evil and not designed properly for use with headphones (Because if it was, companies like Corda and Woo couldn't hawk multi-thousand dollar components to us!)) instead of their mobile devices, the entire mythos about their "hard to drive" qualities would've never started up.
> Of course, the converse problem is now that the HE-6 is out, and just as bad as the K1000 from years gone by, the 70x gets grouped in the same schema of "hard to drive" with it. So now you've got people convinced that you need a 6W headphone amplifier (which you don't need for anything), for 70x.


 
   
  I hear ya, I hear ya!
  Maybe someone else is listening, too!


----------



## proton007

Quote: 





obobskivich said:


> They aren't inefficient though, unless your point of reference is a Beats Pro or A.00 or something equally insane (you know, 120-130 dB/V - like a boss). Seriously, by pre-iPood standards they really don't stand that exotically apart, and if the original reviewers back in 2006 had tried them from home hi-fi equipment or similar (which we all "know" is evil and not designed properly for use with headphones (Because if it was, companies like Corda and Woo couldn't hawk multi-thousand dollar components to us!)) instead of their mobile devices, the entire mythos about their "hard to drive" qualities would've never started up.
> Of course, the converse problem is now that the HE-6 is out, and just as bad as the K1000 from years gone by, the 70x gets grouped in the same schema of "hard to drive" with it. So now you've got people convinced that you need a 6W headphone amplifier (which you don't need for anything), for 70x.


 
   
  No!! the 70x needs more juice to get the best out of it!


----------



## proton007

I also have this question. Does it make sense to use impedance cables/adapters? 
  I mean if your headphone is already so low impedance that you have to use such a cable/adapter, you don't really need to use an amp either. To me it just feels like holding your ear from around your head rather than just directly.


----------



## maverickronin

Quote: 





proton007 said:


> I also have this question. Does it make sense to use impedance cables/adapters?
> I mean if your headphone is already so low impedance that you have to use such a cable/adapter, you don't really need to use an amp either. To me it just feels like holding your ear from around your head rather than just directly.


 
   
  Do you mean just a straight series resistor?  That's usually just silly.  You'll either ruin the damping factor on a dynamic or screw up the FR on BA IEM.
   
  BA IEMs can benefit from an impedance matching resistor network when used with a high Z out source or just as attenuation if the source is too noisy.


----------



## obobskivich

proton007 said:


> I also have this question. Does it make sense to use impedance cables/adapters?
> I mean if your headphone is already so low impedance that you have to use such a cable/adapter, you don't really need to use an amp either. To me it just feels like holding your ear from around your head rather than just directly.




I have one very specific example that makes the above make sense (aside from the Etyomotic P/S adapters) - the Sony MDR-F1 and MDR-MA900. They are 12 ohms nominal, and include a Zobel to smooth out their impedance (which should make them completely amplifier agnostic in terms of FR changes) - some headphone amplifiers are not stable into 12 ohms, and series resistors could bring those cans up to a higher Z and allow them to work. It will waste power through the resistor, but due to the Zobel it shouldn't cause too drastic a change in the FR. 

With other cans, especially very reactive ones (like HD 600s) you should expect more dramatic changes to the FR. And that's where I agree with Maverick - it's just silly. The Sony example is pretty extreme, and the only other full-size can with such low Z that I'm aware of is the Beyer DT48A.00 - you'd have to wade through the megathread to see what the consensus is on adding Z to that can (it's 5 ohms nominal from the factory). Given that the F1 is out of production, and the A.00 is fairly obscure, that really only leaves the MA900 - and as you said, you probably don't need an amp, so it's unlikely people are buying OTL amplifiers to drive their MA900 and having issues. From an iPod or something it's no problem. 



maverickronin said:


> BA IEMs can benefit from an impedance matching resistor network when used with a high Z out source or just as attenuation if the source is too noisy.




+1.


----------



## Chris J

Quote: 





proton007 said:


> I also have this question. Does it make sense to use impedance cables/adapters?
> I mean if your headphone is already so low impedance that you have to use such a cable/adapter, you don't really need to use an amp either. To me it just feels like holding your ear from around your head rather than just directly.


 
   
  I suppose you could argue that using an adaptor allows you to use the low Z can with a variety of high quality amps. Of course this only makes sense if the combo of low Z can and resistor network sounds better than what you were using before.  So the answer is "it depends".
  As O'Bob was saying, OTLs are off the table. You really only want to do this with a headphone amp with a reasonably low output Z.


----------



## YoengJyh




----------



## Chawanwit

This is the most complex article I have encounter in headfi and I do not understand a thing.55555


----------



## proton007

Quote: 





chawanwit said:


> This is the most complex article I have encounter in headfi and I do not understand a thing.55555


 
   
  Why? Too much maths? I've tried to keep it minimal. I don't know how to make it simpler without removing actual information.


----------



## Chawanwit

proton007 said:


> Why? Too much maths? I've tried to keep it minimal. I don't know how to make it simpler without removing actual information.




Yep I never get math. Anyways really nice useful post about headphone and amp. When I have time I will definitely come back to reread this post so maybe I can gain some new knowledge.


----------



## JohnSantana

ok, supposed we're using headphone amp already, can I still use graphical EQ ?


----------



## xnor

Do you mean a software or hardware EQ? Both can be used with a headphone amp.


----------



## JohnSantana

Quote: 





xnor said:


> Do you mean a software or hardware EQ? Both can be used with a headphone amp.


 
   
  both ?
   
  in this case:
   
  Soft: DENON music apps in iPhone
  Hard: EQ preset button in Fiio E11


----------



## xnor

I'm not sure if I understand the question. But yes, you can use both, even at the same time.


----------



## obobskivich

Just ensure that you don't push the signal/amp/etc into clipping by applying too much boost to a given band. If that makes sense.


----------



## proton007

Quote: 





obobskivich said:


> Just ensure that you don't push the signal/amp/etc into clipping by applying too much boost to a given band. If that makes sense.


 
   
  Agree.
  Push the master down if thats the case.


----------



## JohnSantana

Quote: 





proton007 said:


> Agree.
> Push the master down if thats the case.


 
  master volume from the source ?
  eg. the Windows Media player volume or the source device ?


----------



## chewy4

Quote: 





johnsantana said:


> master volume from the source ?
> eg. the Windows Media player volume or the source device ?


 
  I believe he's talking about the master on the equalizer.
   
  Like if you get clipping, bump down all the bands. Ideally you want the highest band at 0db gain.
   
  EDIT: Although I'm guessing that's not possible with the preset button on the Fiio's.


----------



## JohnSantana

Quote: 





chewy4 said:


> I believe he's talking about the master on the equalizer.
> 
> Like if you get clipping, bump down all the bands. Ideally you want the highest band at 0db gain.
> 
> EDIT: Although I'm guessing that's not possible with the preset button on the Fiio's.


 
  Yes you are right Chewy,
  in my Fiio E11 I cannot see any option to bump it down ? apart from volume knob and the 0 1 2 equalizer preset switch and gain switch.


----------



## chewy4

Isn't the Fiio EQ just a bass boost?
   
  Either way it's designed to not go to clipping levels I would think, so I don't think you would have to worry about it there. You would just have to keep the bands on your software EQ lower if there is clipping.


----------



## polat ozturk

Hi All..
   
    Guys can you help me here.. ı bought a
Pioneer hdj 2000 headphone 

 Lightweight magnesium design
 Protein leather surface with memory foam padding
 Removable Mini XLR connector
 'i-hinge' design with 90° auto return
 Type: Fully enclosed dynamic headphones
 Frequency response: 5 Hz to 30,000 Hz
 Impedance: 36 Ω
 Sensitivity: 107 dB
 Maximum power input: 3,500 mW
 Driver units: 50 mm dome type
 Cord: 1.2-m-long one-side connection coiled type (extended length 3 m)
 Plug: 3.5 mm 3P mini-plug (gold-plated, threaded type)
 Weight: 290 g (without cord)
 Accessories: Carrying pouch, 6.3 mm 3P plug adaptor (gold-plated, threaded type)
   my problem is it sound like 10$ headphono when ı use my desctops onboar soundcard realtech output..Well ım now looking for an dac/amp for my headphone.Yesterday ı found Fiio e10 and ım thinking to buy it.But before that ı just want to be sure if it can fully drive my headphones cans.Iwill write dawn the specs of fiio e10
fiio e10
● Power supply: Standard MINI USB port
 ● Output Power: 150mW(32Ω)
 ● Sample rate USB decoder: 96KHz/24 Bit （Maximum support）
 ● Coaxial output: Stereo PCM
 ● Frequency response: 20Hz~20KHz
 ● Suitable Headphone Impedance: 16Ω~300Ω
 ● Size: 79mm×49.1mm×21mm
 ● Weight: 82g
   
   So.. ı will ask this directly... Will ı be able to listen insanely high volumes without distortion with this fiio e10 dac/amp or not.... if not what would be your adviceses....
   
            Thank you all from now........


----------



## stv014

It should be OK, the low gain mode of the E10 is likely loud enough and is recommended.


----------



## Ruben123

Am I that deaf that I do not hear too huge differences between my Sansa Clip + (near zero Ohm) and the Behringer soundcard (50 Ohm) with a Sennheiser HD 205 II (32 Ohm)?


----------



## xnor

The impedance of the HD205 II seems to be pretty flat so there should only be small frequency response differences.


----------



## stv014

Quote: 





johnsantana said:


> in my Fiio E11 I cannot see any option to bump it down ? apart from volume knob and the 0 1 2 equalizer preset switch and gain switch.


 
   
  The "EQ" on the FiiO E11 is an analog bass boost. If implemented properly, it should not clip unless you set the volume too high.


----------



## Ruben123

Hi xnor, thank you for your response! 
It may explain a lot. Could you tell me how I could find out how flat the impedance is of any headphone? I also own some other headphones and I would like to know if I can use them too with higher impedance sources.


----------



## stv014

Quote: 





ruben123 said:


> Could you tell me how I could find out how flat the impedance is of any headphone?


 
   
  Check the impedance vs. frequency graphs at innerfidelity.com, headphone.com, doctorhead.ru, or goldenears.net. Interestingly, there are some inconsistencies between their measurements, perhaps not all of them measured the impedance while the headphone is on a dummy head (it does makes a difference).
   
  You could also test it yourself, having a source of known high output impedance (or simply whatever you intend to drive the headphones with, to verify that there are no significant frequency response or distortion problems), a splitter, and a PC sound card.


----------



## MrMateoHead

Can anyone help me decode these specifications:
   
  ftp://209.222.7.36/pc/audio/ALC888_DataSheet_1.4.pdf
   
  Headphone output @32 Ohms is given as 1Vrms. Analog power supply current is given as 51 mA. So, my guess is that 1*51 = 51 mW of available power @ 32 Ohms. Output impedance is 1 Ohm. @ 64 Ohms, output should be something like 26 mWs (assuming no additional voltage is compensating for impedance change). At 50 Ohms, which is my actual rated headphone impedance, the estimate would be about 29 mWs. 
   
  I am getting new phones that are rated 35 Ohms, but have appeared to test at 50 Ohms. They are rated 93.4 Db, but unknown if @ 1 mW or 1 Volt RMS (current headset). To reach 110 Db, I would need 16.6 times the power, or, 16.6 mW.
   
  I am finding that manufacturers really don't rate gear consistently. I have been trying to determine what my existing available wattage is, so I can make a better decision about how much I might need later from an amp upgrade.
   
  The Schiit Asgard, for example, has THD + Noise of .1% @ 1 Vrms, but is rated to supply up to 20 Vs between loads of 8-600 Ohms. It is a known 1-watt or so amp, yet I can't figure this out based on their published specs.


----------



## stv014

I have just posted a reply related to this topic in the Computer Audio forum, so I also link it here: how to calculate power and SPL.


----------



## MrMateoHead

Let me add that,
   
  Headphone A is Sennheiser HD 595
  Headphone B is Hifiman HE-400
   
  According to Inner Fidelity,
   
*Senn 595 requires (for 90 Db)*
  0.55 Volt RMS
  0.05 mW
  Impedance is 55 Ohm
   
*Hifiman HE-400 (for 90 Db)*
  .129 Volt RMS
  0.33 mW
  Impedance is 51 Ohm
   
  So, evidently, Hifiman wants 4 time less voltage, and almost 7 times the wattage of the Sennheisers to produce 90 decibels. I don't understand how the Sennheisers require barely a miliwatt to reach 90 decibels. They are rated 112 dB @ 1 Volt RMS. By that figure alone, I would assume 92 dB @0.1 Volt RMS.
   
  I am trying to get myself straightened out.


----------



## stv014

Quote: 





> Originally Posted by *MrMateoHead* /img/forum/go_quote.gif
> 
> Headphone output @32 Ohms is given as 1Vrms. Analog power supply current is given as 51 mA. So, my guess is that 1*51 = 51 mW of available power @ 32 Ohms. Output impedance is 1 Ohm. @ 64 Ohms, output should be something like 26 mWs (assuming no additional voltage is compensating for impedance change). At 50 Ohms, which is my actual rated headphone impedance, the estimate would be about 29 mWs.


 
    
  You can ignore the 51 mA power supply current. It is the maximum voltage of 1 Vrms at 32 Ω that matters, so the power is really 1 * 1 / 32 = 31.25 mW.
  If you took the 1 Ω output impedance from the datasheet of the ALC888, rather than the specifications of your motherboard, or measured it yourself, then note that there is often additional serial resistance (a few tens of Ω) added to the headphone output on the motherboard.


----------



## stv014

Quote: 





> Originally Posted by *MrMateoHead* /img/forum/go_quote.gif
> 
> According to Inner Fidelity,
> 
> ...


 
   
  It is really only 0.055 Vrms, you missed a '0'. That translates to about 115 dB/V, compared to the specification of 112.


----------



## MrMateoHead

Using formulae provided by Inner fidelity and specs, this is what I come up with:
   
  (*edit)
  To reach 110 dB on the Senn 595s:
   
  .055 * 10 (0.55 V)
  0.55^2 / 55 = 5.5 mW for 110 dB
   
  To reach 110 dB on the Hifiman HE-400:
   
  .129 * 10 (1.29 V)
  1.29^2 / 51 = 33 mW for 110 dB
   
  The basic formula was found here:
  http://www.innerfidelity.com/content/nwavguys-heaphone-amp-measurement-recommendations
   
  Assuming all specs and math are correct, either headset should get ear-damaging loud without much wattage at all. My complaint is, I thought getting from 90 dB to 110 dB would require 20 times the voltage, since it is 20 dB, not 10 dB louder. Interestingly, the Hifiman's need about 6 times the wattage to reach the same volume level.


----------



## obobskivich

Assuming current can be delivered ad infinitum, sure. But your voltage # for the 595 is wrong, as per stv014 and InnerFidelity:
http://www.innerfidelity.com/images/SennheiserHD595.pdf

They're more sensitive, it's .055v, not .55v. They will get louder sooner.


----------



## MrMateoHead

Quote: 





obobskivich said:


> Assuming current can be delivered ad infinitum, sure. But your voltage # for the 595 is wrong, as per stv014 and InnerFidelity:
> http://www.innerfidelity.com/images/SennheiserHD595.pdf
> They're more sensitive, it's .055v, not .55v. They will get louder sooner.


 

 Ooops. Corrected above.


----------



## obobskivich

Even 90 dB is insane by the way.


----------



## MrMateoHead

Quote: 





obobskivich said:


> Even 90 dB is insane by the way.


 

 110 would be like a fricking concert, so I believe that! I am just spec-drunk at the moment, and irritated that I cannot figure out whether I'll have 6 times the wattage I need to get the Hifimans as loud as I would likely ever stand. As is, I can't usually stand turning volume much past 50% with my current setup.
   
  I assume the Hifi's are going to suck up a lot of whatever headroom I currently have.


----------



## obobskivich

110 is unrealistically loud - you will have a headache after. 60-70 is realistic.


----------



## xnor

I wouldn't go above 85 dB SPL. The HE-6 requires less than 7 mW (or 0.63 V) to reach that volume. Many headphones only need a tiny fraction of a single milliwatt to reach the same volume.


----------



## MrMateoHead

Quote: 





xnor said:


> I wouldn't go above 85 dB SPL. The HE-6 requires less than 7 mW (or 0.63 V) to reach that volume. Many headphones only need a tiny fraction of a single milliwatt to reach the same volume.


 

 Thanks Xnor. Can you speak to the calculations I made above however, or give any guidance on how to make use of the weird specs given for many headphones and amps? I wouldn't want to listen at 110 dB (or even 100 dB) for more than short bursts. I am usually in a quiet environment where 85 dB or less is probably more than adequete.
   
  It baffles me to think that the HE-6 would require much of an amp to reach high volumes, yet the big hifiman amp for sale puts out something like 6 watts.


----------



## xnor

If you use the Vrms needed to reach 90 dB SPL from innerfidelity just use
   
  10^(relativedB / 20) and multiply it with the Vrms needed to reach 90 dB SPL.
   
  So for 85 dB SPL you have to substract 5 dB SPL: 10^(-5 / 20) * 0.055 = 0.031 Vrms for the HD595 to reach 85 dB SPL.
   
  You can reverse this: 20*log10(0.031 / 0.055) = -5 dB.
   
  If you have sensitivity for milliwatts just use 10*log10(power / 0.001) instead, or the reverse: 10^(... / 10).


----------



## MrMateoHead

Quote: 





xnor said:


> If you use the Vrms needed to reach 90 dB SPL from innerfidelity just use
> 
> 10^(relativedB / 20) and multiply it with the Vrms needed to reach 90 dB SPL.
> 
> ...


 

 Ok - the first formula makes sense and I can replicate your number. 85 dB is achieved at 0.031 Vrms for the senns, and 0.0725 for the hifimans.
   
  Hypothetical, lets Change the Vrms to 1.
   
  20*Log(10*(1 / 0.33)) = 30 dB. Therefore, 1 Vrms yields max SPL of 112 dB. (Hifiman)
  20*Log(10*(1 / 0.055)) = 45 dB. Therefore, 1 Vrms yields max SPL of 135 dB (Sennheiser)
   
  Though, both of those numbers are pretty close to radically high. Realistic? Or is it likely that driver limits would prevent such SPL? I am surprised that 1 V could yield that much volume considering amps like the Asgard are rated for up to 7 Vrms (but 1 Vrms at 10% THD).


----------



## obobskivich

Power requirements are often misrepresented to sell more gadgets - you really don't need anywhere the "juice" most traderags cry about. As far as when the driver blows up - the isodynamic should outlast because it will like die due to Tmax not Xmax, while the Sennheiser you'll probably pop the cone or cook the motor off fairly quickly (max input power is probably like 200 mW). But there will be time relativity here - instantaneously they will survive more than continuously. But still - this is way beyond suitable listening levels.


----------



## mikeaj

I couldn't follow what you're trying to calculate, but before we even get to that, people have been using log10( ) to be shorthand for logarithm with base 10.  Somehow a 10 ended up inside the argument of your logarithms.
   
  Senn HD 595 (0.055 Vrms for 90 dB SPL):
  20*log10(1 / 0.055) = 25.2 dB,
  so 1 Vrms would give 90 dB + 25.2 dB = 115.2 dB SPL
   
  HiFiMAN HE-400 (0.129 Vrms for 90 dB SPL):
  20*log10(1 / 0.129) = 17.8 dB,
  so 1 Vrms would give 90 dB + 17.8 dB = 107.8 dB SPL


----------



## MrMateoHead

Quote: 





mikeaj said:


> I couldn't follow what you're trying to calculate, but before we even get to that, people have been using log10( ) to be shorthand for logarithm with base 10.  Somehow a 10 ended up inside the argument of your logarithms.
> 
> Senn HD 595 (0.055 Vrms for 90 dB SPL):
> 20*log10(1 / 0.055) = 25.2 dB,
> ...


 

 Thanks for correcting me.
   
  The problem is that I suck at using my own calculator. I haven't used Log forever. The sequence for me is 20*log(1 / 0.129), for example.
   
  I have been trying to figure out how to calculate headphone SPL based on Vrms and other specs I am unused to. A lot of headphones and amps do not report mW as I might expect.


----------



## xnor

Quote: 





mrmateohead said:


> Ok - the first formula makes sense and I can replicate your number. 85 dB is achieved at 0.031 Vrms for the senns, and 0.0725 for the hifimans.
> 
> Hypothetical, lets Change the Vrms to 1.
> 
> ...


 
   
  As mikeaj wrote, log is the short for logarithm with base 10. So if 10^x = y then log(y) = x. Another notation is lg.
   
  The 115 dB SPL mikeaj calculated is right and "close" to the specs (112 dB SPL @ 1Vrms, 1 kHz) provided by Sennheiser. Of course, the sound pressure level cannot scale linearly until infinity. Most drivers struggle to produce 120 dB SPL at low frequencies.
   
  To calculate dB SPL @ 1 mW from @ 1 Vrms use this: dBSPL@1Vrms - 10*log(1000 / impedance)
   
  For the HD595 this is 112 - 10*log(1000 / 55) = 99 dB SPL @ 1mW.


----------



## MrMateoHead

Quote: 





xnor said:


> As mikeaj wrote, log is the short for logarithm with base 10. So if 10^x = y then log(y) = x. Another notation is lg.
> 
> The 115 dB SPL mikeaj calculated is right and "close" to the specs (112 dB SPL @ 1Vrms, 1 kHz) provided by Sennheiser. Of course, the sound pressure level cannot scale linearly until infinity. Most drivers struggle to produce 120 dB SPL at low frequencies.
> 
> ...


 

 You're the man. As noted, there is some sense that this math can under or over-estimate SPL at a given power level.
   
  I just got my Hifimans in the mail today. I am currently assaulting them with a battery of music, and I can see that given my lower power output, the "loudness" of the recording influences whether or not I feel like I need another volt or two. The HE's are very deceptive however, as they are quite "relaxed" and smooth even at higher volumes so far. I'll be playing with them for awhile trying to decide what a realistic long-term volume need it. I am leaning toward a headstreamer atm, though I would love to get my hands on a creek OBH 11 or some other discrete honey. For the sake of simplicity however, I am leaning toward DAC combos.


----------



## chewy4

I didn't see this being discussed in here and was wondering about something:

 Are planar magnetics immune to impedence mismatches? Meaning that it is unneccesary to follow the 1/8th rule?
   
  If you take a look at Tyll's charts on them, they have near flat FR and phase with 600Ohms impedance going in to them. But they are generally low impedance HPs.


----------



## Steve Eddy

Pretty much, yup. Planars are a virtually purely resistive load. They don't have that same low frequency resonance that dynamic drivers do. That's why my LCD-2 Rev. 2's sound just fine when driven by the 390 ohm output impedance of my TEAC A-H500 integrated amp's headphone jack.
   
  se


----------



## NA Blur

I figured I would supply a comment here about one of your equations.
   
  "
_A few notes for those who want to dig deeper_:
Electrical:

 Impedance is a complex (number) load, Z = R + jX, where R is 'resistance' and L is 'reactance', both of them represented in Ohms. This can also be written as Magnitude,|Z| and Phase θ."
   
  You talk about L as the reactance, but your equation uses X.


----------



## mikeaj

Quote: 





na blur said:


> I figured I would supply a comment here about one of your equations.
> 
> "
> _A few notes for those who want to dig deeper_:
> ...


 
   
  Somebody skipped a step.  L is the common symbol for inductance.  X is generically used for the magnitude of the imaginary component, the reactance (measured in ohms).  For an inductor, it's omega * L, with omega being the frequency (angular, in radians).  For a capacitor, it's - 1 / (omega * C), with C being the capacitance.  See here:
http://en.wikipedia.org/wiki/Electrical_reactance


----------



## Steve Eddy

Looks like a simple typo to me. He wrote L instead of X.
   
  se


----------



## chewy4

Quote: 





steve eddy said:


> Pretty much, yup. Planars are a virtually purely resistive load. They don't have that same low frequency resonance that dynamic drivers do. That's why my LCD-2 Rev. 2's sound just fine when driven by the 390 ohm output impedance of my TEAC A-H500 integrated amp's headphone jack.
> 
> se


 
  Awesome, thanks.


----------



## proton007

Quote: 





steve eddy said:


> Looks like a simple typo to me. He wrote L instead of X.
> 
> se


 
   
  Fixed it. Thanks to SE and NA Blur


----------



## oscar704

```
Power = Antilog ( (Required SPL - SPL per mW)/ 10).
```
  does anyone know what is the "Required SPL" is? im guessing its Dynamic range but i want to confirm, if not, what is it and why?


----------



## mikeaj

oscar704 said:


> ```
> Power = Antilog ( (Required SPL - SPL per mW)/ 10).
> ```
> 
> does anyone know what is the "Required SPL" is? im guessing its Dynamic range but i want to confirm, if not, what is it and why?




Read that "required" as "desired". SPL is the sound pressure level, which is the sound pressure in dB referenced to 0 dB being the lower limit of audibility (a chart may help). So hopefully as you might expect, the louder you listen, the more power needs to be delivered to the headphones.

If you are listening to a recording with a wide dynamic range, the loud parts are much louder than the average or soft parts, and the peaks may be briefly much louder than the rest. In that case, then you could require more power (higher peak volume) just to keep the average level about the same compared to a different recording with a smaller dynamic range.


----------



## stv014

The best way to find out the desired SPL is to actually measure it. Find the highest volume setting you would want to use while listening to music, then, without changing anything else, replace the music with a sound file containing 1 kHz sine wave at 0 dBFS level (lower level is OK, too, but you will need to compensate the measured/calculated SPL accordingly). You can then either measure the voltage on the headphones using a splitter and a DMM (make sure that the DMM is accurate at the frequency of the test tone) and calculate the SPL from the voltage and the sensitivity of the headphones, or use an SPL meter to measure the actual loudness. The accuracy will be limited by not knowing the sensitivity of the headphones exactly in the first case, and in the second case the measured value will be affected by factors like the seal and distance from the driver, but it is possible to get a reasonable estimate. Add a few dB of headroom for amplifier power requirement calculations. You may end up being surprised how little power is really needed to drive headphones at a non-ear damaging level.


----------



## jcx

depending on listening scenario, dynamics of the music  20+ dB of headroom can be reasonable
   
http://www.head-fi.org/t/583300/what-makes-some-amp-better-than-others#post_8469465


----------



## stv014

Note that I wrote testing with a 0 dBFS sine wave after listening to music that requires the highest volume setting. So, the peaks in the music are already accounted for, the extra few dB is only an additional safety margin.


----------



## proton007

I've changed the 'required' to 'desired'. Makes more sense.


----------



## xezi

Quote: 





doublea71 said:


> So the player's output impedance should be less than the earphone's impedance...is there an ideal ratio between the two?


 
  Hmm... not sure if you're still interested in this question but... let's give it a try...
   
  Yes, there is a theoretical, ideal ratio. Zearphone/Zout should be ideally infinite.
  Other words, Zout should be ideally zero. This holds on the earphone end,
  but not for all circuitry, meaning that some mid-stages (some modern ic amplifiers)
  are current driven, not voltage driven, and in these cases that is not necessarily true.
   
  In practice, however, you see amp specs like this: I can deliver 30mW to a 32ohm headphone,
  but only 10mW to a 120ohm load, for example. The maximum power an amp will deliver
  is, of course, defined by design, and the delivered power at any specific load goes by V^2/Z. 
  That's a nonlinear relationship, but you can see the bigger the earphone impedance, the lower
  the power the amp will give. You can see nothing was said about the output impedance, 
  but that's implied in the 30/32 10/120 spec.
   
   
  Now, one should understand that the output impedance of an active element (such
  as an amplifier) is a v/i, dynamic, frequency dependant, relationship, not a physical resistor.
  This is important because, if one thinks about maximum _power transmission_ through the amplifier,
  the ideal ratio would be 1, that is, the earphone impedance should be exactly the
  same as the output one. For example, with a fixed frequency source (your power outlet
  is an example), suppose you connect a 6ohm resistance in series (that would be your
  output impedance), and after it you will try some lamps, say, a 3ohm, 6ohm, 12ohm, 1000ohm.
  The lamp that will bright the most is the 6ohm one.


----------



## xnor

Yeah but the power transfer theorem is about choosing a load resistance with a given (fixed) source resistance. In your lamp example you'd be best off not adding the resistor at all (assuming the lamp can handle that).


----------



## xezi

Quote: 





xnor said:


> Yeah but the power transfer theorem is about choosing a load resistance with a given (fixed) source resistance. In your lamp example you'd be best off not adding the resistor at all (assuming the lamp can handle that).


 
  Hi Mr. Threepwood , yes, that was for the sake of the example... the resistance would be
  the output impedance of an amplifier, in a system with fixed frequency. The resistor would
  already be part of the system, say, inside the power outlet.


----------



## EasySounds

First I'd like to say thank you for this very helpful thread.
   
  I'm still struggling to understand how to figure out how much power I need.
   
  Say I'm comparing the headphones Hifiman he-500 (38Ω and 89db) and the amp fiio e07k (> 220 mW@32Ω /> 250 mW@16Ω).
   
  Using the formula you provided: inverse log ( (desired db - headphone db) / 10 ) I got 0.398 (if I desired 85b) or 0.398 x 10^(-3) (if I desired 65db). 
   
  I assume the answers are in watts: so 85db meant 398mw and 65db meant 3.98mw? I'm really confused. 
   
  Also, would it matter if the resistance of the headphone is out of the range of the resistance of the amp? Or is this not how it works?
   
  Thanks.


----------



## xnor

The headphone datasheet at IF says it needs 0.31 V to reach 90 dB SPL. That's about 87 dB/mW (using the measured impedance at 1 kHz of 47 ohms) or 100 dB/V.
   
  10^((85-87)/10) = 0.631 mW, yes that is milliwatts, in watts: 0.000631 W
   
  10^((65-87)/10) = 0.00631 mW


----------



## marcus49371

nice thx for the reference


----------



## proton007

Quote: 





marcus49371 said:


> nice thx for the reference


 
   
  Sure np.


----------



## Tom22

hi there i was just wondering if there is even a need to amp a low impedence headphone like the noontec zoros? if so how much of a difference does it make? i'm currently thinking about getting a fiio e 7 or 11 and maybe he fire eye mini
   
  this is from innerfidelity
Impedance and phase plots show a 20 Ohm headphone with some modest resonances at 2kHz and 6kHz, likely originating from resonances behind the driver. With 16mVrms needed to achieve 90dB at the ear this is a _very_ efficient headphone, and will easily be driven to loud levels from portable players. But the isolation plots shows that this headphone does not isolate well at all making this a headphone that can be used portably, but not for listening in loud environments. On the other hand, you will be able to remain aware of your surroundings, so using these cans portably in quite neighborhoods will work well.


----------



## proton007

Quote: 





tom22 said:


> hi there i was just wondering if there is even a need to amp a low impedence headphone like the noontec zoros? if so how much of a difference does it make? i'm currently thinking about getting a fiio e 7 or 11 and maybe he fire eye mini
> 
> this is from innerfidelity
> Impedance and phase plots show a 20 Ohm headphone with some modest resonances at 2kHz and 6kHz, likely originating from resonances behind the driver. With 16mVrms needed to achieve 90dB at the ear this is a _very_ efficient headphone, and will easily be driven to loud levels from portable players. But the isolation plots shows that this headphone does not isolate well at all making this a headphone that can be used portably, but not for listening in loud environments. On the other hand, you will be able to remain aware of your surroundings, so using these cans portably in quite neighborhoods will work well.


 
   
  Innerfidelity is pretty spot on with their analysis. From the data it seems it doesn't really require an amp.


----------



## Tom22

Quote: 





proton007 said:


> Innerfidelity is pretty spot on with their analysis. From the data it seems it doesn't really require an amp.


 
  thanks, for your reply, what would an amp even do anything? change in sq?


----------



## obobskivich

tom22 said:


> thanks, for your reply, what would an amp even do anything? change in sq?




Louder (so you can go deaf faster). If your current "thing" is noisy or has massive channel imbalance (you'd know about both of these, no question about it) it might change that, depending on how you source the signal into it - but by and large: louder.


----------



## Tom22

Quote: 





obobskivich said:


> Louder (so you can go deaf faster). If your current "thing" is noisy or has massive channel imbalance (you'd know about both of these, no question about it) it might change that, depending on how you source the signal into it - but by and large: louder.


 
  thats perfect response! even better i can save some cash!
   
  i always thought an amp would boost all the frequencies (bass,mids and treble) ( the noontec zoros have a sharp notch at about mid treble) figured an amp could fix that
  i was wondering then wouldn't the noontec zoros be a gem then? its low impedence and its relatively flat signature perfect for portable use!
   
  why would anyone want headphones that have a high impedence even if its for home use ? if all it does it suck up more power? Hypothetically two headphones were identical in sound quality but the difference in impedence, logically the lower impedence is more economically friendly?


----------



## obobskivich

tom22 said:


> i always thought an amp would boost all the frequencies (bass,mids and treble)




If it boosted all frequencies it would just increase the overall signal (= louder). But it will do *nothing* of the sort (at least not as you're proposing) - all an amplifier will (should) do is apply gain to the signal (that is, make the signal larger); it does not magically improve (or transfigure) the sound quality. Depending on the interaction with the load it is presented, and relatively speaking, it may act on the frequency domain to an extent, but an EQ is a better bet if you want "big, dramatic, night and day" changes, and if you're looking to change something on the time or radiative domain - look at the speakers/headphones. 



> why would anyone want headphones that have a high impedence even if its for home use ? if all it does it suck up more power? Hypothetically two headphones were identical in sound quality but the difference in impedence, logically the lower impedence is more economically friendly?




Impedance is not a "quality" or "performance" spec, despite what a lot of marketing suggests. It's just a characteristic of a given driver - some will be high impedance by nature, some will be low impedance by nature, and there is no rule of thumb that one is better than another. Higher impedance doesn't actually even require more power (power requirement is determined by sensitivity and your target SPL (which should always be <85)), but it *may* require relatively proportionally more voltage (which is why some portable devices have problems with some high impedance headphones). 

Generally with headphones sold for at-home use, the designer/manufacturer doesn't have to care either way, because the assumption is (or at least was, for many years) that you're plugging them into a stereo receiver or integrated amplifier which will drive its headphone jack with the "main" amplifier section built into it (with resistors in the way, to protect both ends). Usually these devices will put out a few watts per channel for headphones (which is more than any ten people should ever need; seriously). However that's changed in recent years, and people have started to want to take their headphones with them and plug them into things like CD players and iPods (which have inherently limited voltage swing, due to their battery power). So this is where low impedance headphones have an edge. 

It's all relative, basically - if you're talking from the perspective of an AC powered integrated amplifier or CD player, it really truly doesn't matter what specifications your headphones have; if you're talking from the perspective of an iPod, it's better go with low impedance and high sensitivity, to get the best out of the device (and the less it has to put out, the longer the battery lasts); if you're talking from the perspective of a marketier - oh good lordy, your headphones better be at least one trillion ohms, and your amplifier's output better have negative impedance across it, so that you can show fantasy numbers with a ton of 0's and tell the customers about specifications (that have no actual bearing on their lives) and move more units. :tongue_smile:


----------



## Tom22

Quote: 





obobskivich said:


> If it boosted all frequencies it would just increase the overall signal (= louder). But it will do *nothing* of the sort (at least not as you're proposing) - all an amplifier will (should) do is apply gain to the signal (that is, make the signal larger); it does not magically improve (or transfigure) the sound quality. Depending on the interaction with the load it is presented, and relatively speaking, it may act on the frequency domain to an extent, but an EQ is a better bet if you want "big, dramatic, night and day" changes, and if you're looking to change something on the time or radiative domain - look at the speakers/headphones.
> Impedance is not a "quality" or "performance" spec, despite what a lot of marketing suggests. It's just a characteristic of a given driver - some will be high impedance by nature, some will be low impedance by nature, and there is no rule of thumb that one is better than another. Higher impedance doesn't actually even require more power (power requirement is determined by sensitivity and your target SPL (which should always be <85)), but it *may* require relatively proportionally more voltage (which is why some portable devices have problems with some high impedance headphones).
> 
> Generally with headphones sold for at-home use, the designer/manufacturer doesn't have to care either way, because the assumption is (or at least was, for many years) that you're plugging them into a stereo receiver or integrated amplifier which will drive its headphone jack with the "main" amplifier section built into it (with resistors in the way, to protect both ends). Usually these devices will put out a few watts per channel for headphones (which is more than any ten people should ever need; seriously). However that's changed in recent years, and people have started to want to take their headphones with them and plug them into things like CD players and iPods (which have inherently limited voltage swing, due to their battery power). So this is where low impedance headphones have an edge.
> ...


 
  thanks for your time in writing that  response, i really enjoyed reading it =) i'm still new to the specs on headphones and been only watching some youtube videos about them saying things like (bigger drivers= more bass) i now feel like an idiot listening to that. 
   
  i am using an iphone 3gs and i'm trying to look for an eq that fixes the noontecs notch at about 4k cause otherwise i'm very pleased with all other aspects of the headphone except the lack of isolation
   
  the iphone eq is pretty hard bad, you can't make a custom one, so i found myself leaving it alone (the knotch at 4k doesn't really matter too much to me but i would like the possiblity to fix that if i so choose)


----------



## obobskivich

tom22 said:


> thanks for your time in writing that  response, i really enjoyed reading it =) i'm still new to the specs on headphones and been only watching some youtube videos about them saying things like (bigger drivers= more bass) i now feel like an idiot listening to that.




I think the biggest problem with discussions about audio, is the risk of over-generalizing. For example, bigger drivers _can_ mean more bass, but by themselves do not guarantee it. 



> i am using an iphone 3gs and i'm trying to look for an eq that fixes the noontecs notch at about 4k cause otherwise i'm very pleased with all other aspects of the headphone except the lack of isolation
> 
> the iphone eq is pretty hard bad, you can't make a custom one, so i found myself leaving it alone (the knotch at 4k doesn't really matter too much to me but i would like the possiblity to fix that if i so choose)




Does Accudio have the Zoros in its database? I also remember hearing about an Audyssey app for iDevices that includes an EQ - might look into that. I'm sure both of these cost money btw.


----------



## radioguy1

Quote: 





obobskivich said:


> It's all relative, basically - if you're talking from the perspective of an AC powered integrated amplifier or CD player, it really truly doesn't matter what specifications your headphones have...


 
   
  This is reassuring, but I still wonder if these (relatively expensive) headphones I'm about to buy might have any sound degradation or distortion because the headphones have such low impedance.  I'm about to buy Sony MDR-7520 headphones, specs say impedance is 24 Ohms.  My old home receiver is a Denon DRA-275R, specs say amplifier impedance is 8 Ohms.  That's less than the 1:8 impedance load ratio that's suggested.  Do you think they'll still sound good?
   
  Other specs on the headphones: closed-ear, sensitivity is 108 dB/mW, power handling is 4,000mW, frequency response is 5-80kHz, driver size 50.0mm.  Thanks!


----------



## xnor

The amplifiers output impedance is 0.1 ohm, but that's the _speaker _output. The headphone output on receivers is usually in the hundreds of ohms. Yamaha for example uses 470 ohm on many of their receivers.
  I doubt you'd even come close to the 1/8th rule on most receiver headphone jacks even if your headphones had an impedance of several hundred ohms.


----------



## radioguy1

Thank you very much, xnor!


----------



## MrMateoHead

Quote: 





xnor said:


> The amplifiers output impedance is 0.1 ohm, but that's the _speaker _output. The headphone output on receivers is usually in the hundreds of ohms. Yamaha for example uses 470 ohm on many of their receivers.
> I doubt you'd even come close to the 1/8th rule on most receiver headphone jacks even if your headphones had an impedance of several hundred ohms.


 

 That is extremely high impedance. Why, given the impacts of high output impedance on phones, would manufacturers do that? Are there any brands known for having really good headphone jacks?


----------



## mikeaj

Quote: 





mrmateohead said:


> That is extremely high impedance. Why, given the impacts of high output impedance on phones, would manufacturers do that? Are there any brands known for having really good headphone jacks?


 
   
  Doesn't cost much to just put a big resistor between the speaker amp output and the headphone jack and call it a day. (Adding extra parts to implement a headphone amp most people wouldn't use would cost money.) Plug headphones in, and for many you'll get a reasonable volume. For plenty of headphones, this won't particularly alter the sound much; for others, it could be different, but different isn't necessarily worse. (well, usually it is, in these scenarios)
   
  That said, I think a lot of those class D chip amps these days include an integrated headphone amp in the chip, so that's kind of a freebie that can be used instead that may have decent specs for driving headphones.


----------



## shaocaholica

Hypothetically, what can happen if speaker level input is fed into a headphone amp?  Lets assume all different kinds of powered amps here.


----------



## xnor

It depends on the design of the headphone amp.
  
 With something like the O2 the op amps in the gain stage could "die", or you'll at least get extreme clipping. With other headphone amps you may be fine but only if you turn the volume control all the way down. Still, I wouldn't suggest hooking up a headphone amp to a speaker amp, not even using the headphone jack of the amp/receiver. We have line-outs with standardized line levels for a reason.


----------



## shaocaholica

Thanks.  So what exactly is 'line-out standardization'?  As in, what are the expected maximum levels?  How can I measure a source to see if its in spec?  I have a 'Pro' Denon cassette deck DN-790R which has its HP output tied to its line out (by design) with no volume adjustment on the HP out.  Its way too loud to drive any HP and I'm just going to hook it up using a passive limiter (Art Headtap) but I'm curious how I can measure the Denon's output to see how high it can go.  What kind of instrument can I use?  Can I use a DMM with Vrms and say a 440hz tone with the record levels at max?  Pink noise?


----------



## stv014

Use tones at a few frequencies (some DMMs are only usable in a rather narrow frequency range). Something like 50 or 60 Hz, and 400 or 1000 Hz. If you are lucky, the measured levels will not differ too much (for example, I get less than 1% variation in the range 30 to 2000 Hz with a cheap old DMM, but others might be much worse, especially some newer cheap ones with "true RMS" capability). Otherwise, if there is a large difference, you should probably trust the value at 50-60 Hz. It is also recommended to measure how much the level drops with a resistor load, and calculate the output impedance.


----------



## xnor

We have the consumer -10 dBV which is about 0.316 Vrms and pro audio (usually balanced) +4 dBu which is about 1.228 Vrms. Those are nominal levels. Professional equipment for example may have headroom up to +24 dBu so there won't be clipping up to about 12.3 Vrms.
  
 CD players usually output 2 Vrms for a full-scale sine wave, as do some DACs.


----------



## stv014

Perhaps related to this topic, I did some tests on how the output impedance of the amplifier affects the distortion of dynamic headphones. The headphone tested was a DT880 Pro (250 Ω), using sine sweeps at 0.68 and 0.22 Vrms voltage on the drivers at 1 kHz, and with output impedances of 10.3 Ω (Xonar Essence STX headphone output) and ~110 Ω (using 100 Ω serial resistors).
  
 Unfortunately, the measurements at low levels contain too much microphone and ambient noise. At the higher level, I repeated the tests twice, to be able to verify the repeatability of the results. The sweeps played were equalized so that the SPL and frequency response are matched at the low and high output impedance. The graphs below assume that 1 Vrms voltage on the driver at 1 kHz produces 100 dB SPL. This is probably not accurate, but the levels on each graph should be consistent nevertheless. Only the right channel was tested.

 These are the results I got (click to zoom):
  
 Frequency response: from left to right: microphone, headphone driver, amp output
        
 THD vs. frequency: from left to right: microphone, headphone driver, amp output
        
 Driver impedance vs. frequency:


 Increasing the output impedance of the amplifier does indeed seem to increase the bass distortion of the driver, especially around its resonance frequency. This cannot be explained with the amp "working harder" (see graphs), or the headphone having to produce a higher SPL in the bass range (because it is equalized). The effect is not major, however, it is a difference of about 2 dB, but it is there. With a low impedance source that is equalized to match the frequency response of a high impedance one - which is what I did  - the distortion is lower than it is with actual high output impedance.
  
 Although the effect probably varies depending on the headphone model, and some are more affected than others. It would be interesting to try the same with orthodynamic headphones, to confirm if they are not only a more or less purely resistive load, but also fairly linear as well.


----------



## proton007

Hi guys,
 After searching for a simpler way to explain these concepts to the many people who ask for advice, I've added a Hydraulic Analogy in the beginning. I think it can help form a good abstraction for the concepts in the proceeding sections.


----------



## eujaee

Thank you, proton007.  Your explanation of electrical dampening was the easiest to understand of all the ones I read.  Your article is very useful and informational, thank you for taking the time.


----------



## proton007

eujaee said:


> Thank you, proton007.  Your explanation of electrical dampening was the easiest to understand of all the ones I read.  Your article is very useful and informational, thank you for taking the time.


----------



## Flisker

First of all I would like to say thank you proton007 for taking your time and effort to get all this information together, especially "Hydraulic Analogy" is great, there are some minor things that gets me little confused, but otherwise I think I get the point perfectly. 
  
 Second thing is that when it comes to formulas I get little lost. 
  
*Mainly here :*
  
Use this formula to calculate the power needed:

```
[color=#808080]Power = Antilog ( (Desired SPL - SPL per mW)/ 10). Note that a 3dB increase in SPL will cause a 2x increase in Power. For reference, 85 dB is considered to be the limit where long term exposure can cause hearing damage. Use 85dB to calculate the average power needed.[/color]
```
  
 Deduced that SPL is sensitivity, 85 dB is "ideal volume" but thats where it ends for me 
	

	
	
		
		

		
			




  
 I don't want to waste your time, but if you get some to spare, could you please show me and maybe other electrical newbies example of explained calculation ? 
  
 Got data here :
  
*Sennheiser HD700*
 - Nominal Impedance : _150Ω_
 - Max Impedance : _370Ω @ +-120hz_
 - Sensitivity : _105dB (Characteristic sound pressure level (at 1 KHz) - 105 dB SPL (1 kHz, 1 Vrms))_
 - THD : _0.03% (1 kHz, 1 Vrms)_
  
*FiiO E12*
 - Drive ability : _16~300Ω (recommend)_
 - Output Power : _>880mW@32Ω_
 - THD : _<0.005%_
 - Output Impedance :_ <0.5Ω_
 - Input Sensitivity :_ <710 mV(Gain:high)_
 - Signal to Noise Ratio : _>110dB_
 - MAX input Level : _>8 Vrms_
 - MAX output voltage : _15.5 Vp-p_
 - MAX output current : _170 mA_
 - Channel imbalance : _<0.5dB_
  
 Your opinion on these two would mean a lot to me. Thanks in advance.
  
 Sources :
http://en-us.sennheiser.com/downloads/download/file/3329/HD_700_GB_542592_low.pdf
 http://graphs.headphone.com/graphCompare.php?graphType=0&graphID[]=3808&scale=30
http://fiio.com.cn/products/index.aspx?ID=100000038732625&MenuID=105026001
  
 ps : Liked the avatar-bold text matched color


----------



## Flisker

Did some research, found some data 
  

  
  
 If I understand this right than to get "maximum" out of HD700 I need amp which will provide me enough... to talk in your analogy "pressure" - 6.16Vp-p and and "amount of water" - 14.52mA right ? As for volume , 31.62mW ?
  
 When I look at E12 specs I feel like I ordered nuclear power plant for my small garden sprinkler. (31.62mW for 120dB ... and E12 has max output 880mW ... oh guess I may be getting it while writing this 
	

	
	
		
		

		
		
	


	




 880mW at 32ohm not 150)
  
 But still voltage and current required in table looks pretty low.


----------



## xnor

According to http://www.head-fi.org/t/668238/headphones-sensitivity-impedance-required-v-i-p-amplifier-gain HD700 needs a gain of -1 dB with a 2Vrms source to reach 110 dB SPL with a full-scale sine wave.
  
 E12 has a high gain of roughly 10 dB according to jude, 0 dB low gain.


----------



## Flisker

xnor said:


> According to http://www.head-fi.org/t/668238/headphones-sensitivity-impedance-required-v-i-p-amplifier-gain HD700 needs a gain of -1 dB with a 2Vrms source to reach 110 dB SPL with a full-scale sine wave.
> 
> E12 has a high gain of roughly 10 dB according to jude, 0 dB low gain.


 
  
 Oh, I feel totally dumb to be honest, because those numbers don't tell me anything. 
  
 - How did you find out that HD700 needs -1dB gain ? What does it even mean ? Isn't gain like multiplier so it is always positive ?
 - What's 2Vrms at source ?
  
 - Do you think E12 is good amp to go with HD700 ? Why ?
  
 I guess I'll have to take some class on these things 
	

	
	
		
		

		
		
	


	




 
  
E: "*S@1V* is the sensitivity with 1 V, 500 Hz sine wave input in dB SPL." HD700 has 105 but at 1000 Hz does it change things ?


----------



## xnor

flisker said:


> - How did you find out that HD700 needs -1dB gain ? What does it even mean ? Isn't gain like multiplier so it is always positive ?
> - What's 2Vrms at source ?
> 
> - Do you think E12 is good amp to go with HD700 ? Why ?
> ...


 
  
 Sensitivity is either specified for 1 V or 1 mW. It's often not specified but V usually means Vrms = Volt root mean square.
 2.83 Vpp / 2 = 1.41 Vp / sqrt(2) = 1 Vrms
  
 It's usually specified at 1 kHz, but in my table I used 500 Hz where possible. Since the HD700 has flat mids it doesn't change, so 105 dB SPL @ 1 Vrms it is.
  
 Your source outputs some max RMS level. CD players often output 2 V, the Apple devices about 1 V max, the Sansa Clip+ about 0.5 V max.
  
 If we want 110 dB SPL we need to add 5 dB to the HD700's sensitivity.
 +5 dB = 10^(5/20) = 1.78x * 1 V = 1.78 V
  
 If we have a 2 V source we actually need negative gain (attenuation): 1.78/2  = 0.89x, in decibels: 20*log(0.89) = -1 dB
  
 So if you indeed have a 2 V source you can theoretically achieve 111 dB with 0 dB gain, or 121 dB with +10 dB gain.
 If your source only outputs 1 V you have to subtract 6 dB.
 If it only output 0.5 V you have to subtract another 6 dB, so 12 dB in total, and so on...
  
  
 edit: From what I can tell the E12 seems like a good choice, especially since it has a gain switch.


----------



## Flisker

xnor said:


> Sensitivity is either specified for 1 V or 1 mW. It's often not specified but V usually means Vrms = Volt root mean square.
> 2.83 Vpp / 2 = 1.41 Vp / sqrt(2) = 1 Vrms
> 
> It's usually specified at 1 kHz, but in my table I used 500 Hz where possible. Since the HD700 has flat mids it doesn't change, so 105 dB SPL @ 1 Vrms it is.
> ...


 
  
 Thanks for formulas.
  
 Is it this just about volume ? I got already enough volume from PC - ALC889 Chip - http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PFid=28&Level=5&Conn=4&ProdID=173
  
 I'am more concerned about raising audio quality, don't think that HD700 will perform at it's "best" just from ALC889 integrated chip on pc motherboard.


----------



## xnor

The gain values reported by jude seem to be completely off btw, because the specs say >16 dB for high gain....
  
  
 edit: Yeah that's just about volume, but the E12 definitely performs better than onboard audio.


----------



## Flisker

xnor said:


> The gain values reported by jude seem to be completely off btw, because the specs say >16 dB for high gain....


 
  
 Yea, it's because early version of E12 had 0 or 10dB gain, now it's 0 or 16dB. I'am getting new so the one with 0/16.


----------



## xnor

Oh that's good to know.


----------



## Flisker

Main thing I still can't figure out is, what does this
  

  
 actually mean in real world audio performance 
  
*FiiO says :* _"Based on this formula, we have worked out the power, voltage and current for some popular headphones. In order to get the best sound effect, you can refer to the power required by 120dB sound pressure and peak voltage required by high dynamic."_
  
 Well if I look at E12 at their page, it says :
  
 - Output Power : _>880mW@32Ω_
 - MAX output voltage : _15.5 Vp-p_
 - MAX output current : _170 mA_
  
 Therefore by their information E12 should be kind of overkill to use with HD700 because it got nearly 30 times more output power than should be needed, 3 times more output voltage and 10 times more output current. So I'am thinking "what the he..". Why would someone use Schiit Lyr or some other much much stronger amp with these.


----------



## xnor

The table is wrong because it assumes the 105 dB SPL is based on 1 mW which it isn't. The headphone produces 105 dB SPL with 1 V.
  
 According to E12 specs the 15.5 Vpp max output are 5.5 V.
 5.5V into 150 ohms = 200 mW max.
  
 Since we've already established that for 110 dB you need 1.78 V, into 150 ohms = 21 mW.
 So the E12 produces about 10x more max power with high gain and max volume.
  
 For 95 dB SPL the HD700 needs about 0.66 mW.


----------



## Flisker

xnor said:


> The table is wrong because it assumes the 105 dB SPL is based on 1 mW which it isn't. The headphone produces 105 dB SPL with 1 V.
> 
> According to E12 specs the 15.5 Vpp max output are 5.5 V.
> 5.5V into 150 ohms = 200 mW max.
> ...


 
  
 How did u get 5.5V ?


----------



## stv014

flisker said:


> How did u get 5.5V ?


 
  
 15.5 / 2.8284; the 2.8284 is the square root of 2 (the ratio of the peak and RMS level for a sine wave) multiplied by 2.
  
 By the way, according to these measurements, the E12/Mont Blanc can actually output 6.5-7 Vrms into 150 Ω. The 15.5 Vp-p is specified for 32 Ω, where the measured level was more like 5 Vrms.


----------



## xnor

See #170 for conversion from Vpp to Vp to V (rms).
  
 15.5 / 2 / 1.41 = 5.5 V


----------



## Flisker

stv014 said:


> 15.5 / 2.8284; the 2.8284 is the square root of 2 (the ratio of the peak and RMS level for a sine wave) multiplied by 2.
> 
> By the way, according to these measurements, the E12/Mont Blanc can actually output 6.5-7 Vrms into 150 Ω. The 15.5 Vp-p is specified for 32 Ω, where the measured level was more like 5 Vrms.


 
  
 Great, thanks 
	

	
	
		
		

		
		
	


	




 
  


xnor said:


> See #170 for conversion from Vpp to Vp to V (rms).
> 
> 15.5 / 2 / 1.41 = 5.5 V


 
  
 Yea, guess I can see it there now. Tbh I'am mentally destroyed for today and have to wake up early, will continue with thinking about all provided information tomorrow.
  
 Thanks a lot, really appreciate your help


----------



## ultrabike

stv014 said:


> Perhaps related to this topic, I did some tests on how the output impedance of the amplifier affects the distortion of dynamic headphones. The headphone tested was a DT880 Pro (250 Ω), using sine sweeps at 0.68 and 0.22 Vrms voltage on the drivers at 1 kHz, and with output impedances of 10.3 Ω (Xonar Essence STX headphone output) and ~110 Ω (using 100 Ω serial resistors).
> 
> Unfortunately, the measurements at low levels contain too much microphone and ambient noise. At the higher level, I repeated the tests twice, to be able to verify the repeatability of the results. The sweeps played were equalized so that the SPL and frequency response are matched at the low and high output impedance. The graphs below assume that 1 Vrms voltage on the driver at 1 kHz produces 100 dB SPL. This is probably not accurate, but the levels on each graph should be consistent nevertheless. Only the right channel was tested.
> 
> ...


 
  
  
 Is it possible to generate the THD plots in dBV instead of %?


----------



## Flisker

stv014 said:


> By the way, according to these measurements, the E12/Mont Blanc can actually output 6.5-7 Vrms into 150 Ω. The 15.5 Vp-p is specified for 32 Ω, where the measured level was more like 5 Vrms.


 
  
*So ... it can not be calculated this way -> *
  


xnor said:


> According to E12 specs the 15.5 Vpp max output are 5.5 V.
> 5.5V into 150 ohms = 200 mW max.


 
  
 ?
  
 Found out how _"__5.5V into 150 ohms = 200 mW max."_ works _->_ _"P = V2/ R" _is it right formula ?
  
 Than the correct output power would be _"72/150=326.6 mW" ?_ 
  
*Also what about max impedance* ? Nominal is actually only lowest impedance. 
  
 So shouldn't we calculate with max impedance ?
  

 This graph shows 370ohm@120Hz so _"72/370=132.4 mW"  _would be more correct ?
  
*Lastly I think we still got something wrong.*
  
 Because when I look here - http://www.head-fi.org/t/620082/lake-people-g109-g103-thread
  
 There are specs for some amp with different ohms already calculated.
  
_Max. output level:  _
_> 18.8 Veff in 600 ohms = 590 mW_
_> 13.8 Veff in 100 ohms = 1900 mW_
_> 10.7 Veff in 50 ohms = 2300 mW_
_> 7.8 Veff in 50 ohms = 1900 mW_
_> 3.7 Veff in 16 ohms = 410 mW_
  
 Veff should equal Vp-p if I didn't get it wrong and when I do calculations nearest number I got was 540mW but no luck with 590 
	

	
	
		
		

		
			




  
 When used formula_ "V=Vp-p/2.8284"_ and _"P=V2/R"_ I end up absolutely off.


----------



## proton007

Two things;
 Pavg = Average power, calculated using Vrms
 Pp-p = Max possible power,  calculated using Vp-p.
  
 In the lake people specs, V-effective means Vrms.
  
 Most of the times, Vrms is the unit used in AC specs.


----------



## Flisker

proton007 said:


> Two things;
> Pavg = Average power, calculated using Vrms
> Pp-p = Max possible power,  calculated using Vp-p.
> 
> ...


 
  
 Ah, now it works _"18.82/600=590"_


----------



## stv014

ultrabike said:


> Is it possible to generate the THD plots in dBV instead of %?


 
  
 Yes. I used % because I thought it is a more familiar distortion unit for most people. I still have the recorded WAV files, though, so I can generate more graphs (including separate D2 and D3) if needed.


----------



## stv014

> Originally Posted by *Flisker* /img/forum/go_quote.gif
> 
> This graph shows 370ohm@120Hz so _"72/370=132.4 mW"  _would be more correct ?


 
   
You should generally use the nominal impedance, since that is approximately the impedance at 1 kHz, and the sensitivity of the headphones is typically also specified at 1 kHz. An amplifier with very low output impedance is basically a voltage source (as long as it can supply the required current), so it does not need to output a higher voltage at 120 Hz than at 1 kHz, otherwise it would not have a flat frequency response. You can view the increased impedance at 120 Hz as increased efficiency, due to the fact that the driver resonates at that frequency (requiring less power to produce the same SPL).


----------



## ultrabike

stv014 said:


> Yes. I used % because I thought it is a more familiar distortion unit for most people. I still have the recorded WAV files, though, so I can generate more graphs (including separate D2 and D3) if needed.


 
  
 Makes sense. It's just a thought.
  
 The reason I asked is because I think % is relative to fundamental. For the headphone and microphone measurements, the fundamentals with the different series resistors have the same level, so % distortion are directly comparable. For the amp out measurement however, the fundamentals have different levels.
  
 It might also be helpful to see all plots in dBV to compare distortion of headphone driver and amp out relative to a reference voltage instead of the different fundamentals.


----------



## lisagorbin

My head wants to explode reading the stuff here. So if you don't mind I'll ask a question directly. Is the fiio e11 amp a good enough match with the grado sr80i? my source is sansa fuze+. I'm on a tight budget for the amp so the fiio e11 is all i can afford to get if ever. Thank you.


----------



## Neug

Hi sound science,

I've been trying to get my head around damping. So i decided to make a spreadsheet to tell me how much source resistance increases the reverberation decay time of a signal at system resonance. I used a closed box model (is this ok for open headphones?) to get the Qtc of a system with and without source resistance. I estimated T-S parameters based on plots from inner fidelity, I know thats not very accurate but I was looking for ballpark figures for Qms and Qes. What I found so far was that using a dampening factor of 8 would increase the decay time by a few percent. I'm yet to convert the decay time to reference a more usable measure like a drop in db. Here's the spreadsheet if anyone wants to correct/look/play. Blue fields are inputs.

Neug


----------



## Steve Eddy

Hello, Neug.

First, the word you should be using is "damping," not "dampening." Damping refers to the control of the speaker's resonance which is what you're talking about here. Dampening refers to the absorption of sound inside the enclosure. For example, you would call the fiberglass or poly fill stuffing inside a speaker enclosure "dampening material."

Second, I'm not sure just what decay you're talking about. You use -60dB as reference, which to me sounds like you're talking about reverberation decay, i.e. RT60 which is used to describe the reverberation time within an acoustic space. Is that what you're referring to or something else?

se


----------



## Neug

steve eddy said:


> Hello, Neug.
> 
> First, the word you should be using is "damping," not "dampening." Damping refers to the control of the speaker's resonance which is what you're talking about here. Dampening refers to the absorption of sound inside the enclosure. For example, you would call the fiberglass or poly fill stuffing inside a speaker enclosure "dampening material."
> 
> ...




Thanks for the corrections. Post edited. I'm not familiar with a lot of the terms of acoustics. Yes it's reverberation decay, exactly (mathematically).

Neug


----------



## Steve Eddy

neug said:


> Thanks for the corrections. Post edited. I'm not familiar with a lot of the terms of acoustics. Yes it's reverberation decay, exactly (mathematically).




So you're trying to figure out the reverberation decay of a pair of headphones? Presumably while they're being worn? I'm afraid that's not making any sense to me seeing as the acoustic space between the drivers and the wearer's head is incredibly small. Nor do I see how the speaker's Qtc would have any effect whatsoever on the RT60 of an acoustic space. That's a function of the acoustic space, not the driver or loudspeaker. Where did the RT60 figures in your spreadsheet come from?

se


----------



## Neug

I'm calculating 2.2*Qtc/fc. The speaker in a closed box has a Q and resonant frequency so it should have a decay time. Maybe reverberation time is the wrong word.
  
 Cheers
              Neug


----------



## Neug

Lecture on Decay of oscillations.
  
 Neug


----------



## Steve Eddy

Ok, so basically what you're talking about is what would rather commonly be called ringing.

se


----------



## VGoghs earfrmsc

Many thanks for this post, very informative


----------



## Noob Meister Jr

proton007 said:


> Use this formula to calculate the power needed:
> 
> ```
> Power = Antilog ( (Desired SPL - SPL per mW)/ 10).Note that a 3dB increase in SPL will cause a 2x increase in Power.For reference, 85 dB is considered to be the limit where long term exposure can cause hearing damage.Use 85dB to calculate the average power needed.
> ```


 

 Dude, antilog? log base what? if log base 10 then the antilog(z) = the number x such that logx=z. So if this is base 10 then if log_10(x)=z, 10^z = x, or if base e then exp(z)=x; writing it like this is much less confusing then antilog(z), especially when otherwise the base is complete guesswork.
  
 Using this formula in the way you describe leads me to believe that if your headphone sensitivity is greater than 85db/MW then you don't need an amp. Is this what you are trying to say? It doesn't matter what base the log because anything to the power of a negative number is less than 1, so as long as your amp can put out 1MW of power at your highest ohmage of your headphones then you're all fine and dandy.
  
 e.g. if db/MW were 85 = desired SPL then antilog(0)=1, any base whatsoever; thus if an amp can supply 1MW at the peak impedane for my headphones (300ohms), then yahoo to the $2 shop for an amp I go.
  
 This would seem to go against all other advice I've ever heard.
  
 What do you think? Have I calculated something wrong?


----------



## mikeaj

The figures are all decibels, so base 10 would seem like the most reasonable guess, right? (It's base 10)
  
 For what it's worth, a lot of people listen with peak levels much above 85 dB SPL. Peaks being tens of dB higher than average levels isn't common on highly compressed loudness wars'd releases, but it is on other masters. Your amp should cover the peak levels, not just the average.
  
  
 But yeah, unless you're listening pretty loudly the average levels are often achieved at well below 1 mW of power. After all, most headphones are in the 90s or 100s dB sPL / 1 mW range.


----------



## LibiSC

Hi.
  
 If I have a fiio e07k
  
  
 220mw at 32 ohms
  
 a headphone with 100 ohms impedance
  
 100 db @100mw
  
  
 i want 70 decibels ... What percentage should the amp be with a gain o 6db?


----------



## BauerFIve

Learned a lot from this post, thank you.


----------



## red71rum

I was reading over some of this thread at work and have a quick question. Have you guys ever run into the situation where the source seems to powerful for the headphones that you are using? Let me explain, I have a HisoundAudio Studio 3rd Aniversary and I usually use it with my Senn Amperiors, ATH M50, AKG K280. But when I hook it up to say my UE triple Fi 10's, I only can handle say, gaving it on volume 1, it is clear but too loud for me.


----------



## KamijoIsMyHero

Its due to a higher sensitivity of the iem


----------



## red71rum

kamijoismyhero said:


> Its due to a higher sensitivity of the iem


 

 That is what I thought after reading through this, just wanted to make sure I was not crazy or had overly sensitive ears.


----------



## Tom22

red71rum said:


> That is what I thought after reading through this, just wanted to make sure I was not crazy or had overly sensitive ears.


 
 thats why a lot of portable devices don't need amps imo, i think amps nowadays are really just equalizer, (expensive equalizers)
  
 abeit cleaner than the presets on the iphone etc.. but still most headphones (in the consumer market) are able to run fine off say an iphone/ s3 or whatever device usually. 
  
 nowww i use the fiio e6 with my re400 because it gives it just enough oomph on the bass and a bit emphasis on the lower treble without making it overblown. (none of the presets on my itouch can do that without screwing the rest of the sound up)


----------



## Voltmod

Lots of good info here. One question, will my Fidelio X1s sound better with an Astro Mixamp than my 470 Ohm headphone jack receiver? From what I understand, the receiver headphone impedance is too high for the X1s. Mixamp would be a better fit and has great Dolby Digital surround features for 360 / PS3.

 You'd think getting a receiver to plug all your stuff into was an end-all-confusion solution... Now nothing will plug into my receiver, sigh.


----------



## MunDa

very informative. thank you very much.


----------



## MonarchX

I just joined because I was interested specifically in this subject. I am not an audiophile, but I do like to have quality hardware to use for games. I had a really hard time following the OP because it is filled with science and that only confused me... I would appreciate someone could help me out and answer my questions in layman's terms/simple English, but I do understand some technical terms, which you will hopefully realize if you continue reading my post/reply.
  
 I used to use Creative X-Fi Titanium with Astro A50s headset (SPDIF), which was a total net value of $300. Now I use ASUS Xonar DGX (10ohms) running UNi drivers and Sennheiser HD-280 Pro (64ohms) headphones (analogue connection), which is a total net value of only $150. However, my current setup is miles better in sound quality than my previous setup! I do not have the best sense of hearing, but I could tell that my current setup sounded much better and it was NOT a placebo effect. I can now hear sounds I never heard before and Sennheiser HD-280 Pro headphones are monitoring headphones, so they have no artificial bass or similar frequency boosters.
  
 Since I am not big on audio, I am very content with what I have clarity-wise and sound-quality-wise. My problems rests in the fact that while I love Sennheiser HD-280 Pro headphones, I do not like Dolby Headphone positional audio that much due to high levels of reverberation and echo, even when used with an improved 7.1 Shifter profile that comes with UNi drivers. I heard SBX Pro solution in action/live and found it to be absolutely awesome and superior to Dolby Headphone. The trouble is that only Sound Blaster Z supports SBX Pro and Sound Blaster Z is rated at 22 ohms. My headphones are rated at 64ohms! That means there is a HUGE mismatch! *Does that mean there is a big chance that I will frequently experience distorted sound?* I am not into high volume and killing my ear-drums. I like medium-level sound that is pleasant and loud enough for me to hear footsteps behind me. Right now my ASUS Xonar DGX is rated at 10ohms, while headphones are at 64ohms. That is ALSO a mismatch, isn't it? Its not as drastic as it would be with Sound Blaster Z... I am not hearing any distortions and all frequencies sound very clear to me. But how could it also be a mismatch if ASUS Xonar DGX offers specific headphone options for headphones with sub-32ohms, 32-64ohms, and above 64 ohms? It obviously supports headphones with ohms less than 8x the soundcard ohms (10ohms)... Otherwise it would have options for headphone with 80ohms and above!!! So, I am at a loss as to whether I should get Sound Blaster Z or not. I know it would improve my positional audio experience, but it would worsen my overall quality sound, wouldn't it?
  
 Can this issue be resolved with a cheap amp? Cheap, but good enough to be better than trying to match 22ohm Sound Blaster Z and 64ohm Sennheiser HD-280 Pro headphones. I am a bit confused about digital vs analogue signal in relation to impedance. Impedance does NOT affect digital signal, correct? Someone told me that I should get an amp and connect it to my Xonar DGX via SPDIF and then connect my headphones to the amp via analogue... Or maybe it would be cheaper to just upgrade my headphones to some above (8x22) 176 ohms?
  
 All in all, I want to get to that SBX Pro sound without sacrificing the non-positional audio quality aspect for as little $ as possible, be it with an amp or with new headphones... Of course, if the negative effect of mismatched 22ohm soundcard and 64ohm headphones is not that severe, then I may as well just get the Sound Blaster Z soundcard and be on way enjoying SBX Pro technology. Of course if you know how to reduce Dolby Headphone reverberation by some 50%, then it would be the best solution!!!
  
 Thank you for your time and help in advance!
  
 Sincerely,
 The New Guy


----------



## mikeaj

Yeah, I'm not much a fan of Dolby Headphone either.
  
 With respect to headphone impedance "mismatches" the effect on the sound is generally marginal on most sets. To be honest, it's more on the HD 280 than most headphones because the impedance vs. frequency plot looks like this:

 source: InnerFidelity   http://www.innerfidelity.com/images/SennheiserHD280Pro.pdf
  
 The effect with the 22 ohms on the Sound Blaster Z (I'm assuming you got this info from a good source and did not verify on my own) should be below a 2 dB swing in frequency response, giving effectively a slight bump in that 90 Hz range. Also, you'll get a little bit more nonlinear distortion. It'll affect the sound slightly but nothing I'd be actually concerned with.
  
 The headphone options on the Asus sound cards seems to just limit the volume on some settings. It doesn't change anything really with regards to the hardware configuration or amplification. The labels for headphone impedance are some kind of gross oversimplification that veers into the "misleading" category.
  
 This can be resolved by using a cheap amp, yes. If you already have a dedicated sound card I would use the analog output of the sound card and not the digital S/PDIF. If you use S/PDIF, you need something with S/PDIF input, which would be a device that also has a DAC inside. You only need an amplifier if you want something with lower output impedance to resolve this issue (or "issue").


----------



## MonarchX

Thank you! The whole Dolby Headphone, CMSS-3D, SBX Pro deal is crazy. They are nothing, but feature licenses, capable of being applied to any soundcard, including onboard Realtek codecs... For example, top-end MSI Z97 Gaming motherboards use Realtek ALC1150 onboard audio, but licensed to produce SBX Pro Surround Sound, which is really the best surround sound solution out there. I bet my Xonar DGX can do it too, but it will never be licensed to do so...


----------



## ab initio

mikeaj said:


> source: InnerFidelity   http://www.innerfidelity.com/images/SennheiserHD280Pro.pdf


 
  
 Holy crap, I just realized the title of the graph says it was measured with a _600 Ohm output impedance_. Does this not artificially muck with the phase information?
  
 Shouldn't this measurement be conducted with a source with as low as possible output impedance (it should be easy to find an amp with negligible output impedance compared to any headphone) and the current and current phase be measured as a function of frequency? I don't understand what a 600 ohm load is doing in there. Maybe somebody can help me out?
  
 Cheers


----------



## stv014

ab initio said:


> Holy crap, I just realized the title of the graph says it was measured with a _600 Ohm output impedance_. Does this not artificially muck with the phase information?


 
  
 No, it is possible to calculate the impedance (and phase) vs. frequency of a load from the voltage falling on it when driven by a source with any known non-zero output impedance. One of the utilities from the last link in my signature does exactly that. Actually, an output impedance comparable to that of the load makes the measurement more accurate than if it was close to zero (in that case, the current should be measured instead, but ADCs that expect a voltage input are obviously more common).


----------



## Tyll Hertsens

Measuring it with a high output impedance allows the cans to be as undamped as possible and lets the phase swing more easily for a strong response when measured.  Since all the cans are measured similarly, it allows for better relative evaluation.


----------



## ab initio

tyll hertsens said:


> Measuring it with a high output impedance allows the cans to be as undamped as possible and lets the phase swing more easily for a strong response when measured.  Since all the cans are measured similarly, it allows for better relative evaluation.




So does the mechanical vibration affect the impedance results? And is that a fair assessment on the headphone when they should be driven by a low impedance source (isn't that what headphones are designed for)? The electrical damping would change the mechanical response.

Tyll, i love your site and your measurements. It is a great resource to the headphone community! Thanks

There are still a bunch of missing pages in your headphone measurement explaination and im anxious for those to get posted 

Cheers


----------



## stv014

If the driver is reasonably linear, it can be modeled as a network of resistors, capacitors, and inductors, which do not change significantly with different sources. For example, the impedance peak at the primary resonance frequency can be simulated with a parallel RLC circuit. In any case, even with a higher source impedance, the driver itself as a load remains the same. However, mechanical factors like whether the headphones are actually worn do have an effect on the measured impedance curve.
  
 Edit: here is a comparison of the same headphone measured with damping factors of about 23 and 2.3. This might not be perfectly accurate, since even a small error in the assumed output impedance can skew the results in the high damping factor case, but it does show there is no significant difference in the resonance peak with increased source impedance:


----------



## r010159

How much of a damping ratio would provide the best sonic results? Some say 8-10. Some people with tube amps run at about 5 or thereabouts. One person I ran into told me at least 20. Personally, I think I have noticed a difference between a 8 and a 10 damping factor. Wouldn't too low of a damping factor distort both the high and low FR? Basically have mid-frequency bloat? Instead would this depend on the specific amp? Or maybe how linear the impedance curve is on a set of headphones?

If this has already been discussed, please provide me with a URL.


----------



## SilverEars

stv014 said:


> If the driver is reasonably linear, it can be modeled as a network of resistors, capacitors, and inductors, which do not change significantly with different sources. For example, the impedance peak at the primary resonance frequency can be simulated with a parallel RLC circuit. In any case, even with a higher source impedance, the driver itself as a load remains the same. However, mechanical factors like whether the headphones are actually worn do have an effect on the measured impedance curve.
> 
> Edit: here is a comparison of the same headphone measured with damping factors of about 23 and 2.3. This might not be perfectly accurate, since even a small error in the assumed output impedance can skew the results in the high damping factor case, but* it does show there is no significant difference in the resonance peak with increased source impedance*:


 
 but, from the graph, it shows that the magnatude has changed along with the shift.


----------



## stv014

silverears said:


> but, from the graph, it shows that the magnatude has changed along with the shift.


 
  
 The difference is insignificant (note: do not compare the left vs. right graphs, but the blue vs. red traces on the same graph instead), and is mostly the result of measurement inaccuracy. The analysis utility needs to know the output impedance exactly for correct results, and when it is low, even 0.1 ohm error will visibly skew the graphs (especially with the zoomed in Y scale I used). Additionally, the slight (~1 degree at 23 kHz) phase difference in the high frequency range is probably because the sound card output that was used for testing has some serial inductance, and since that is not taken into account by the analysis (which assumes pure resistive input and output impedances), the low output impedance case is skewed towards measuring a less inductive load. In any case, the reactance in that range is mostly from voice coil inductance, rather than back EMF. I could do the test again with 1000+ ohms output impedance, but I would expect it to match the 110.7 ohms measurement fairly accurately, probably better than what the above graphs show, since the source inductance becomes insignificant relative to the resistance.


----------



## SilverEars

LO has high output impedance.  How come?  What difference does it make if output impedance of the line out was significantly different like 20ohms vs 400ohms?


----------



## ed45

Very informative thread, but I have a question that I couldn't find the answer to here:  Is there a primer on head-fi that provides instructions (for an amateur like myself) for measuring the output impedance of a headphone amp, presumably using a multimeter? Is it possible to measure the impedance from the output jack without opening up the amp?


----------



## stv014

ed45 said:


> Is it possible to measure the impedance from the output jack without opening up the amp?


 
  
 Yes. You just need a (possibly DIY) cable that makes it possible to measure the output voltage, and at the same time connect a load (preferably a resistor) to the output. Use any software of your choice to generate a sine wave at a frequency where the AC voltage mode of the multimeter works reasonably well (it does not even need to be perfectly accurate, since it is only the ratio of the voltages that will matter), and measure the voltage with and without the load under otherwise identical conditions. It is easier to get accurate results if the resistance of the load is not very different (by orders of magnitude) from the output impedance, but it obviously should not be so low as to risk damaging the amplifier. Something like 33 to 100 ohms should be OK at <= 1 Vrms unloaded voltage.
  
 Once you have measured the voltages and know the load resistance, you can use the following formula:
  
 Zout = Zload * ((V_unloaded / V_loaded) - 1)
  
 A somewhat more advanced topic is measuring the output impedance as a function of frequency, for example with capacitor coupled outputs. This can be done with a sound card loopback; I have a program that can generate impedance vs. frequency graphs, but a simple RMAA frequency response test is enough to show if there is significant output reactance (e.g. capacitor coupling causes a low frequency roll-off, from which the capacitance can be calculated). With simple multimeter-only testing, one could measure at a low and mid-range frequency (e.g. 50 and 400 Hz) to see if there is any serial capacitance.


----------



## Useraid

Have new pair of 4 driver earphones which need to be treble boosted on all sources except when attached to speaker + amp (B&W MM1 in this case) does this tend to indicate portables are too weak to drive earphones?


----------



## mindbomb

One of the things I don't understand is how peak sound pressure levels relates to general volume settings. I have an audio technica ad700 (98db/mw, 32 ohm) connected to an amp that can do 1.3v, 90mA, 1 ohm output impedance. That comes out to 115db peak, but I find that I'm frequently using the low end of the analog pot(it's an Alps) + about -15db of digital volume control to get a reasonable volume. Now, what would it be like if I switched to a q701(105db/v), with a peak of 107db? And I assume if I got a k612 (101db/v) and had a peak of 103db/v, that would just be unusable? Also considering an sennheiser hd 380 (110db/v), which would have a peak of 112db. That sounds like it would be pretty close to the audio technicas, but idk if it works out like that.


----------



## Vasiliosn

Hi, i have an old receiver from sony which has an input of 50k ohms and input sensitivity at 500mv my question is if i can use this input for good results with headphones like the Hd650 or Hd 700. I use the receiver with my Hd 598's and works perfectly...


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## mindbomb

vasiliosn said:


> Hi, i have an old receiver from sony which has an input of 50k ohms and input sensitivity at 500mv my question is if i can use this input for good results with headphones like the Hd650 or Hd 700. I use the receiver with my Hd 598's and works perfectly...


 
 the input specs only tell you that you can plug in an ipod with a line out cable(which is 500mv), and things like that.


----------



## SilverEars

stv014 said:


> A somewhat more advanced topic is measuring the output impedance as a function of frequency, for example with capacitor coupled outputs. This can be done with a sound card loopback; I have a program that can generate impedance vs. frequency graphs, but a simple RMAA frequency response test is enough to show if there is significant output reactance (e.g. capacitor coupling causes a low frequency roll-off, from which the capacitance can be calculated). With simple multimeter-only testing, one could measure at a low and mid-range frequency (e.g. 50 and 400 Hz) to see if there is any serial capacitance.


 
 Calyx coffee is a great example of the roll off from output capacitor.  It has a capacitor to block DC offset and this same capacitor reacts with the load outputting a high pass filter response.  Their headphone out has capacitor output.


----------



## Vasiliosn

mindbomb said:


> the input specs only tell you that you can plug in an ipod with a line out cable(which is 500mv), and things like that.


 
 This is my receiver,   http://www.ebay.com.au/ctg/Sony-STR-DE597-6-1-Channel-100-Watt-Receiver-/46557150?_tab=1


----------



## proton007

mindbomb said:


> One of the things I don't understand is how peak sound pressure levels relates to general volume settings. I have an audio technica ad700 (98db/mw, 32 ohm) connected to an amp that can do 1.3v, 90mA, 1 ohm output impedance. That comes out to 115db peak, but I find that I'm frequently using the low end of the analog pot(it's an Alps) + about -15db of digital volume control to get a reasonable volume. Now, what would it be like if I switched to a q701(105db/v), with a peak of 107db? And I assume if I got a k612 (101db/v) and had a peak of 103db/v, that would just be unusable? Also considering an sennheiser hd 380 (110db/v), which would have a peak of 112db. That sounds like it would be pretty close to the audio technicas, but idk if it works out like that.


 
  
 The 'volume' of sound refers to perceived loudness, and is variable in two respects. One, the frequency determines how loud it will sound at a particular dB level, that is, different frequencies at different dB can sound equally loud. It's called the frequency and loudness contour.
  
 Second, this response will vary due to natural variations, occupational effects, and many other individual reasons (listening habits, health issues, age etc).
  
 In addition, the recording itself, the dynamic range and the mastering will also play a role. At the same volume setting, some albums sound louder than others.
  
 So, as such you can determine the dB levels for impedance matching, but volume setting is mostly an exercise left to the listener.
  
 There are some tips in the main topic on page 1, but to add on, remember that our ear is also subject to fatigue and auditory masking (meaning the louder some frequencies get, they hide other frequencies from being perceived), so just keep this in mind when setting volume levels.


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## Ruben123

So... Ive bought a Voodoo-ed Samsung GS1 for driving my IEMs, BUT, no one actually knows the impedance but it should be around 8 Ohms. Does that mean it is a waste of money since my IEMs are 12-50 Ohms? (8x8=64 so none ´fits´)


----------



## stv014

You could measure the impedance yourself, it only requires the following as a minimum:
 - generate a test signal (sine wave) with any suitable PC software, and copy it to the GS1 in a supported file format
 - a test load, ideally a resistor, but even a headphone or IEM can be sufficient if it has a known resistive impedance at a frequency
 - a splitter to be able to measure the voltage on the load, one with 1 female and 2 male 1/8" TRS connectors should be suitable
 - something to measure the ratio of AC voltages with - a cheap digital multimeter, or even the line input of a PC sound card (the HD audio codec on the motherboard is sufficient) with software to analyze RMS levels
 Measure the voltage with and without the load (if it is an IEM or sensitive headphone, make sure it can handle the level used in the test), and then use the following formula to calculate the output impedance:
  
 Z_out = ((V_unloaded / V_load) - 1) * Z_load
  
 Depending on your IEMs, a high output impedance may or may not be a problem. Some have fairly "flat" impedance and will not sound much different, while the effects on multi-driver balanced armature IEMs can be significant. You can check if your model(s) are measured at InnerFidelity, and how much their impedance varies over the audio band.


----------



## thepooh

Hi ! I noticed a strange fact on my Iphone 6, while switching from a 60 ohms headphones Koss Porta Pro to a 16 ohms Sennheiser IE80, I have to raise 10 % more volume on the iem than on the headphones to get the same loudness !
  
 How could a 60 ohms/102 db headphones sound louder than a 16 ohms/125 db iem ?


----------



## stv014

The Sennheiser's sensitivity is probably specified in dB/V, rather than dB/mW, in which case it is not as much more sensitive as the specs would suggest. At InnerFidelity, the Porta Pro was measured to require 47 mV for 90 dB SPL, while it is 36 mV for the IE800 (2013) - not the same as your IEMs, but maybe similar enough. Additionally, if the iPhone has high enough output impedance, the voltage on the IEMs will be lower (by about 2 dB if the output impedance is 5 ohms). There might also be some random manufacturing variation, or the IEMs not having a perfect seal, or the perceived loudness could be affected by frequency response differences.


----------



## thepooh

stv014 said:


> The Sennheiser's sensitivity is probably specified in dB/V, rather than dB/mW, in which case it is not as much more sensitive as the specs would suggest. At InnerFidelity, the Porta Pro was measured to require 47 mV for 90 dB SPL, while it is 36 mV for the IE800 (2013) - not the same as your IEMs, but maybe similar enough. Additionally, if the iPhone has high enough output impedance, the voltage on the IEMs will be lower (by about 2 dB if the output impedance is 5 ohms). There might also be some random manufacturing variation, or the IEMs not having a perfect seal, or the perceived loudness could be affected by frequency response differences.


 

 Thanks mate ! I'm fixed now


----------



## snip3r77

Nice post


----------



## Zizou21

Excellent post! But I'd have to say I couldn't understand it at all. I went fine through the water sprinkler explanation and then I got lost.
  
 I am interested in acquiring a portable amp for my HD558 but got concerned about the part it says it may damage my headphones with a wrong setup.
  
 Should I get a Portable Amp at all? And what one? I've been reading about those FiiO's out there. They look good.


----------



## proton007

zizou21 said:


> Excellent post! But I'd have to say I couldn't understand it at all. I went fine through the water sprinkler explanation and then I got lost.
> 
> I am interested in acquiring a portable amp for my HD558 but got concerned about the part it says it may damage my headphones with a wrong setup.
> 
> Should I get a Portable Amp at all? And what one? I've been reading about those FiiO's out there. They look good.


 
  
 It's fine if you could understand the first explanation...that's the jist of it, the rest is just putting 'measurements' in their proper context so that we can predict and calculate things without having to rely on feel.
 That goes for most science btw. Things are not as hard as they seem.
  
  
 The HD558 would work fairly well, but the impedance bump (250Ohms at 100Hz) would need some power. Best go for a standalone amp if you don't need to carry your headphones around.


----------



## stv014

proton007 said:


> The HD558 would work fairly well, but the impedance bump (250Ohms at 100Hz) would need some power.


 
  
 It does not. It needs low output impedance to maintain a flat frequency response, but the power output at the resonance frequency is actually lower. For a relatively constant power output (1 dB variation over the audio band), one would need an amplifier with ~120 ohms output impedance, but that would add a 7.5 dB bass boost compared to a zero output impedance amplifier.


----------



## proton007

stv014 said:


> It does not. It needs low output impedance to maintain a flat frequency response, but the power output at the resonance frequency is actually lower. For a relatively constant power output (1 dB variation over the audio band), one would need an amplifier with ~120 ohms output impedance, but that would add a 7.5 dB bass boost compared to a zero output impedance amplifier.


 
  
 Thanks for the clarification!
 This would mean a near zero output impedance amp would work, portable or not.


----------



## joegiz

Excellent thread! Helped me get a good handle on impedance. Now if I can find an input source (good cd transport or high res streamer to match my my WA2 and HD800's) I will be all set!!


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## HiFiGuy528

My reference IEM is the Sony XBA-4 & AKG K3003 both are @ 8 Ohms.
  
 http://store.sony.com/4-driver-in-ear-headphones-zid27-XBA4/cat-27-catid-EOL-Headphones-Earbuds
  
 This is a tricky IEM for a lot of solid state amplifiers to drive effectively.  I see that most SS headphone amps if not all are rated to be used with hps between 16-600 Ohms.  Besides the negative effects of high output impedance on an amp when using this IEM (must be 1 Ohm or below), how come amps can't drive this load or not designed to drive it?


----------



## arnyk

stv014 said:


> You could measure the impedance yourself, it only requires the following as a minimum:
> - generate a test signal (sine wave) with any suitable PC software, and copy it to the GS1 in a supported file format
> - a test load, ideally a resistor, but even a headphone or IEM can be sufficient if it has a known resistive impedance at a frequency
> - a splitter to be able to measure the voltage on the load, one with 1 female and 2 male 1/8" TRS connectors should be suitable
> ...


 
  
 As is pointed out, V_loaded V_loaded and V_unloaded are divided out which has the side effect of making the recommended measurements of them with uncalibrated equipment and equipment that only reads out voltage in arbitrary units as good as anything.  Thus $5.95 DVMs and sound card inputs can be used for this measurement as unbelievable as this may seem. 
  
 I put the equation into a spread sheet so that it is easy to do a number of measurements (for example at different frequencies) and have a lot of results with very little effort.
  
 "Drives just about everything well" headphone amps such as the Topping NX1 and Fiio E11 (must be used with inexpensive separate USB power supplies that are isolated from the source) are economical solutions when the source is substandard or unknown in this regard.


----------



## xtroria

hifiguy528 said:


> My reference IEM is the Sony XBA-4 & AKG K3003 both are @ 8 Ohms.
> 
> http://store.sony.com/4-driver-in-ear-headphones-zid27-XBA4/cat-27-catid-EOL-Headphones-Earbuds
> 
> This is a tricky IEM for a lot of solid state amplifiers to drive effectively.  I see that most SS headphone amps if not all are rated to be used with hps between 16-600 Ohms.  Besides the negative effects of high output impedance on an amp when using this IEM (must be 1 Ohm or below), how come amps can't drive this load or not designed to drive it?


 
  
 I'm not an expert at this topic, so there might be some mistakes in my explaination.
  
 Basically, output impedance acts like a resistor, connected in series to your transducer (iem / headphone / speaker). Now when resistor is connected in series, the bigger resistance will take up more voltage.
  
 So if for example you have a 3 ohm output impedance connected to the SE846 which has 5 ohm resistance @ 4khz, the output impedance will take 37.5% of the voltage supplied by the amp.
  
 Compare this to having 0.5 ohm output impedance connected to the same thing. (0.5 ohm IMO is the highest output impedance any dedicated DAP should have) The output impedance will only take 9% of the voltage supplied from the amp.
  
 A pretty big difference, isnt it? Low impedance headphone / iem is known to be "current hungry", as opposed to the high impedance headphones that has "voltage hungry" trait
  
 Oh for additional note, BA driver iems are notorious for their impedance swings. For example, SE846 is rated at 8 ohm, but its lowest impedance is 5 ohm. So, objectively speaking you want the highest output impedance to be 1:10 ratio, based on tyll's statement in his pono review


----------



## arnyk

xtroria said:


> I'm not an expert at this topic, so there might be some mistakes in my explaination.
> 
> Basically, output impedance acts like a resistor, connected in series to your transducer (iem / headphone / speaker). Now when resistor is connected in series, the bigger resistance will take up more voltage.
> 
> ...


 
  
 Pretty good explanation, I  think. Keep up the good work!


----------



## cjl

hifiguy528 said:


> My reference IEM is the Sony XBA-4 & AKG K3003 both are @ 8 Ohms.
> 
> http://store.sony.com/4-driver-in-ear-headphones-zid27-XBA4/cat-27-catid-EOL-Headphones-Earbuds
> 
> This is a tricky IEM for a lot of solid state amplifiers to drive effectively.  I see that most SS headphone amps if not all are rated to be used with hps between 16-600 Ohms.  Besides the negative effects of high output impedance on an amp when using this IEM (must be 1 Ohm or below), how come amps can't drive this load or not designed to drive it?


 

 If you have a low output impedance amp, even if it doesn't say it can drive 8 ohms on the spec sheet, it'll probably be fine.


----------



## arnyk

hifiguy528 said:


> My reference IEM is the Sony XBA-4 & AKG K3003 both are @ 8 Ohms.
> 
> http://store.sony.com/4-driver-in-ear-headphones-zid27-XBA4/cat-27-catid-EOL-Headphones-Earbuds
> 
> This is a tricky IEM for a lot of solid state amplifiers to drive effectively.  I see that most SS headphone amps if not all are rated to be used with hps between 16-600 Ohms.  Besides the negative effects of high output impedance on an amp when using this IEM (must be 1 Ohm or below), how come amps can't drive this load or not designed to drive it?


 
  
  
 If you actually look carefully at the report for this technical test:
  
 http://www.head-fi.org/t/608553/review-comparison-two-flagships-pass-in-the-night-sony-xba-4-review-vs-the-mdr-ex1000-updated-with-7550-and-xba-40#post_8357374
  
 You will find that if finds 5 ohms, not 1 ohm  to be the minimum impedance of the XBA4.
  
 Still tough for your typical headphone amp, but since we have many speakers that have impedance curves this low building a headphone amp to drive the pants off of it should be far from impossible. In fact is has probably been done many times in the form of a low powered high quality amplifier for driving small speakers in small environments.


----------



## mindbomb

How do you calculate how much current an amp is capable of with just the power spec? For example, the jds labs element is 1.5w peak power into 32 ohms. Can you get a max current from that?


----------



## arnyk

mindbomb said:


> How do you calculate how much current an amp is capable of with just the power spec? For example, the jds labs element is 1.5w peak power into 32 ohms. Can you get a max current from that?


 
  
  I = Sqrt (P/R)
  
 I = Sqrt(1.5/32) =  

  
 0.216506  amps


----------



## mindbomb

arnyk said:


> I = Sqrt (P/R)
> 
> I = Sqrt(1.5/32) =
> 
> ...


 
 see, that's what I originally was thinking. But when I applied it to some amps with given max current values, it didn't work out. Like the O2 amp is 200mA but the power spec of 613mW at 33 ohm gives 136mA. The fiio e11k is 92mA, but the power spec of 450mW into 16 ohm gives 167mA.


----------



## arnyk

mindbomb said:


> see, that's what I originally was thinking. But when I applied it to some amps with given max current values, it didn't work out. Like the O2 amp is 200mA but the power spec of 613mW at 33 ohm gives 136mA. The fiio e11k is 92mA, but the power spec of 450mW into 16 ohm gives 167mA.


 
  
  
 The spec gives the absolute maximum under any condition. The calculation gives the maximum under a given condition.


----------



## castleofargh

mindbomb said:


> arnyk said:
> 
> 
> > I = Sqrt (P/R)
> ...


 

 for the O2 the only time I've seen 200mA mentioned it was *peak* current!!! what we usually deal with as power and voltage are RMS values.
 so sqrt(0.613/33)= 0.136rms indeed, but 0.136/0.7=0.194A peak and that's pretty much your 200mA from specs.
  
  
 about the e11k I just can't find any load associated with those 92mA(can't access fiio's website at all), but when nothing is written, it's often into 32ohm(or 16ohm or whatever, when it's not written it's just useless specs in the end). but it so happens to fit nicely with 32ohm this time ^_^
 power is 270mW into 32ohm so I=sqrt(0.27/32)=0.0918A
 for 16ohm you'll get another limit.


----------



## mindbomb

Oh, okay, so I was thinking that the peak current was constant no matter what load. So, atm, if you were wondering if you had enough current or power for a certain headphone at a certain volume, the only way you could know is if the amp manufacturer gives you specs for that specific load?


----------



## jcx

really need a I,V graph - but sometimes you can guestimate most properties of an amp's output limits from hi and low Z output power spec points - if hi Z power is limited by power supply Voltage/output stage Vswing and lo Z drive limited by max output current
  
 with more different load Z power specs sometimes you can even see evidence of output Z - some headphone amps have 10s of Ohms - the Senn HDVD amp is reputed to have 40 Ohms in series with its output


----------



## SearchOfSub

My amp which is a SET tube amp recommends 33 ohm impedence headphones. Headphone I plan to get is rated at 8 ohms impedence. Will there be lot of distortion? would it be ok?


----------



## Ruben123

Depends on the headphone but I guess there will be quite some distortion, as most very low earphones have huge FR differences when not optimally impedance-matched.


----------



## IBPhoenix09

A quick hypothetical question. If I was considering an amp, with a recommended headphone impedance of  32ohm- 600ohm. Does that mean it would damage a pair of headphones rated at 25ohms? I'm looking at getting a pair of AudioQuest's Nighthawks down the road and trying to find a balanced amp to pair with them.


----------



## cjl

It should be fine. The one concern would be if the amp's output impedance is greater than a couple ohms, but even then it wouldn't damage the 25 ohm headphones (it just would not necessarily drive them without audible artifacts/changes to the sound).


----------



## IBPhoenix09

cjl said:


> It should be fine. The one concern would be if the amp's output impedance is greater than a couple ohms, but even then it wouldn't damage the 25 ohm headphones (it just would not necessarily drive them without audible artifacts/changes to the sound).


 
 I see, so even if the amp doesn't damage the headphones it may not be the best match in terms of sound quality. Additionally does using a balanced connection versus single ended change impedance matching concerns? Or is that a non issue?


----------



## cjl

That depends on the design of the amp. If the balanced is identical circuitry to the single ended, just with 2 amps bridged, the balanced will have twice the output impedance (and therefore be worse for low impedance headphones). If the balanced topology is different though, it's difficult to say, and it'll depend on the specifics of the amp.


----------



## IBPhoenix09

cjl said:


> That depends on the design of the amp. If the balanced is identical circuitry to the single ended, just with 2 amps bridged, the balanced will have twice the output impedance (and therefore be worse for low impedance headphones). If the balanced topology is different though, it's difficult to say, and it'll depend on the specifics of the amp.


 
 Ah I see, Thank you for the explanation. I'm having a hard time with this search for an amp to go with them. I guess its a good thing it isn't an immediate purchase.


----------



## mindbomb

What do measurements of phase tell you? Just that you might need more power than you expect?


----------



## proton007

mindbomb said:


> What do measurements of phase tell you? Just that you might need more power than you expect?


 
  
 Hmm... my knowledge is limited in this respect, but I believe phase measurements are reflective of the Inductance properties of the coil. As much as the coil works with an outside voltage source, its own emf will oppose this change.
 So yeah, in some cases, more power may be needed because you'll have to overcome the reverse emf. This may be related to the damping factor.


----------



## waflet

Hideeho
  
 I am very new to the whole hifi thing, so I am trying to do a lot of reading to get an understanding of how things work. Currently I am having trouble wrapping my head around tube amps. Before I get to my hang up, what I am looking for is a nice tube amp for my HiFiMan HE-400i’s. I started with an SMSL M3 from www.Massdrop.com, but have found its few short comings (it is VERY bright). I am interested in a tube amp to get a more full sound & to play with tube rolling. I want to stay under $200 butdon’t have a problem waiting an extra paycheck or 2 if I need to go over. I have been looking at the Darkvoice 336se, Little Dot MKII, Little Dot I+, Schiit vali2, & Gemtune APPJ. I have been advised that the Darkvoice & Little Dot MKII would not be a good match for my 400i because they are OTL amps.
  
 That is where I am running into an inability to grasp the issue. I had never heard of an OTL amp, so I did some reading on the subject. From what I read OTL amp means Output TransformerLess. By my understanding an amp uses a transformer to convert the 110v input from the wall to whatever the tubes want to see & then uses something else (another transformer or capacitors) to convert to what the headphone wants to see or drives directly from the tube to the headphone (OCL amp). If there is a 2nd transformer to convert the tube output it is a standard amp. If there are capacitors or it drives directly from the tubes it is an OTL amp. Standard amps tend to be either more expensive or cheaper (nice transformers are EXPENSIVE, but cheap ones are very cheap).
  
 Of all the amps I mentioned only the Gemtune has (what I assume is) a transformer in it at all. Are these not all OTL amps? Something like the Schiit lyr2 has 2 transformers in it, so I assume it is not an OTL amp. The reports of the Darkvoice not being perfect for the 400i are fairly universal. The MKII gets some bad marks with the 400i, but there are not as many people reporting so I take that with a much larger grain of salt. The only difference I can see is the recommended headphone impedance listed (which is why I’m posting this question here). Both the Darkvoice & the MKII start listing at 32ohm, while the rest start at either 8ohm or 12ohm. The 400i is listed at 35ohm but I have seen several tests pegging it as high as 40ohm. Would this be the real reason the Darkvoice & MKII aren’t as popular with the 400i crowd? Might this be something like footroom (as opposed to headroom on the top end  ) allowing better sound in low impedance headphones? Are some of these OCL?


----------



## Krutsch

waflet said:


> Hideeho
> 
> I am very new to the whole hifi thing, so I am trying to do a lot of reading to get an understanding of how things work. Currently I am having trouble wrapping my head around tube amps. Before I get to my hang up, what I am looking for is a nice tube amp for my HiFiMan HE-400i’s.
> 
> ...


 
  
 I've listened to an HE-400i and they are nice cans, but low impedance (35 ohm). OTL amps do best with high impedance cans, like 150, 300 and above (e.g. Sennheiser HD-650). Low impedance cans will distort at higher volume (e.g. my Grado or AQ NightHawk).
  
 I think the 400i 'phones were designed to work right out of portable devices. Doesn't mean they won't sound better with more power, but you want a tube amp that works well with low Z cans (i.e. not an OTL).


----------



## waflet

Hideeho
 Thank you very much for making the effort to reply, but you did not answer any of the questions I asked or impart any information or knowledge I did not state in the op.
  
 Do you or does anyone else have an explanation of why the Darkvoice & MKII would not be suitable while the Vali2 & I+ would be even though they all seem to be OTL amps?


----------



## Ruben123

waflet said:


> Hideeho
> Thank you very much for making the effort to reply, but you did not answer any of the questions I asked or impart any information or knowledge I did not state in the op.
> 
> Do you or does anyone else have an explanation of why the Darkvoice & MKII would not be suitable while the Vali2 & I+ would be even though they all seem to be OTL amps?




Do you even need an amp? And if so, get one that doesn't colour the sound.


----------



## waflet

ruben123 said:


> Do you even need an amp? And if so, get one that doesn't colour the sound.


 
 Hideeho
 Thank you for taking the time to respond as well.
 Need? No, but then again I don’t NEED $400 plannar magnetic headphones & could get by with $10 inked headphones.
 The whole point of tube amps in this day & age is specifically to color the sound. If I didn’t want to color the sound I would be looking for a solid state amp & the impedance would not be an issue.


----------



## pinnahertz

waflet said:


> Hideeho
> Thank you for taking the time to respond as well.
> Need? No, but then again I don’t NEED $400 plannar magnetic headphones & could get by with $10 inked headphones.
> The whole point of tube amps in this day & age is specifically to color the sound. If I didn’t want to color the sound I would be looking for a solid state amp & the impedance would not be an issue.


 
 There are other, more flexible, and better ways to color the sound, if that's what you want to do.  What you are essentially doing here is trying to choose an "equalizer" in the form of a tube amp that you will be paying a lot of money for and want to live with for a long time.  Times change, tastes change, different music benefits from different...um...color...so why would to lock into a particular tube amp?  Or will you get lots of tube amps and pick the one you like for a particular situation?  
  
 The whole thing seems a bit like closing your eyes and shooting an arrow at a target that is moving.  You could, for example, get a really good SS amp, then insert resistors between it and your phones.  Resistors cost a few cents, even the really good ones, so you could get a couple hundred different ones to play with and end up with your own boutique sound using only passive components.  Pick out a few favorites, mount them on gold connectors, insert as desired.  Label them "dark", "open", "airy", "vaporous", "glassy", "solid", etc.  Now, doesn't that sound like fun?  And you be the only one with just exactly those combinations.  
  
 Passive...it's such a nice sounding word, isn't it?


----------



## waflet

pinnahertz said:


> There are other, more flexible, and better ways to color the sound, if that's what you want to do.  What you are essentially doing here is trying to choose an "equalizer" in the form of a tube amp that you will be paying a lot of money for and want to live with for a long time.  Times change, tastes change, different music benefits from different...um...color...so why would to lock into a particular tube amp?  Or will you get lots of tube amps and pick the one you like for a particular situation?
> 
> The whole thing seems a bit like closing your eyes and shooting an arrow at a target that is moving.  You could, for example, get a really good SS amp, then insert resistors between it and your phones.  Resistors cost a few cents, even the really good ones, so you could get a couple hundred different ones to play with and end up with your own boutique sound using only passive components.  Pick out a few favorites, mount them on gold connectors, insert as desired.  Label them "dark", "open", "airy", "vaporous", "glassy", "solid", etc.  Now, doesn't that sound like fun?  And you be the only one with just exactly those combinations.
> 
> Passive...it's such a nice sounding word, isn't it?


 

 Hideeho
 What you suggest does sound like fun, but I have to have something to waste my money on. I'm choosing tubes rather than pot or lsd or alcohol (although some in moderation is not too bad of a thing, unless you have to take a drug test for work...) . Honestly tube rolling sounds interesting, so I am trying to learn the hows & whys of it. My op was not meant to be a debate on what amp I need to buy (even out of the ones mentioned), I was looking for information about OTL vs standard amps vs other OTL amps. I am trying to gain some knowledge so I can make a more informed guess as to what amp will best punch the most buttons for me.


----------



## pinnahertz

waflet said:


> Hideeho
> What you suggest does sound like fun, but I have to have something to waste my money on. I'm choosing tubes rather than pot or lsd or alcohol (although some in moderation is not too bad of a thing, unless you have to take a drug test for work...) . Honestly tube rolling sounds interesting, so I am trying to learn the hows & whys of it. My op was meant to be a debate on what amp I need to buy (even out of the ones mentioned), I was looking for information about OTL vs standard amps vs other OTL amps. I am trying to gain some knowledge so I can make a more informed guess as to what amp will best punch the most buttons for me.


 
 I doubt you'll get any useful help.  You're asking for a recommendation that satisfies your current personal preferences.  We don't know them, and they will change.  Research has shown a strong preference for uncolored, neutral sound across a wide population segment.  
  
 You're also into this for the entertainment value of the hardware.  Well, someone might help you there, but their opinion now mesh with yours.  And now you want to go tube rolling?  Our goals are SO different.  I want the best, most accurate, undistorted sound possible. You're asking for something completely different and out of my world.  Probably most other in Sound Science.
  
 You already have the technical and performance differences between general topologies.  Other than that, it's all biases and opinions.  All I could suggest is buy several with return possibility, audition them all, pick your favorite...if you can narrow it down to one.  Personally, I've heard a few very nice tube amps, but never one that offered any advantage over a good SS amp, and what qualities it had, for better or worse, could be obtained better in other ways.  
  
 Oh, and BTW, my name is not Hideeho.


----------



## waflet

pinnahertz said:


> I doubt you'll get any useful help.  You're asking for a recommendation that satisfies your current personal preferences.  We don't know them, and they will change.  Research has shown a strong preference for uncolored, neutral sound across a wide population segment.
> 
> You're also into this for the entertainment value of the hardware.  Well, someone might help you there, but their opinion now mesh with yours.  And now you want to go tube rolling?  Our goals are SO different.  I want the best, most accurate, undistorted sound possible. You're asking for something completely different and out of my world.  Probably most other in Sound Science.
> 
> ...


 

 Hideeho
 My apologies, I left out a very important word in my last post. It should have read "My op was *NOT* meant to be a debate on what amp I need to buy...". That changes the whole sentence completely. My mistake, sorry.
  
 Yes, Pinnahertz, I know your name, hideeho is my greeting. Like hello, or hi, or hideeho neighbor (although I was saw it LONG before Tim Allen had a show).


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## pinnahertz

waflet said:


> Hideeho
> My apologies, I left out a very important word in my last post. It should have read "My op was *NOT* meant to be a debate on what amp I need to buy...". That changes the whole sentence completely. My mistake, sorry.
> 
> Yes, Pinnahertz, I know your name, hideeho is my greeting. Like hello, or hi, or hideeho neighbor (although I was saw it LONG before Tim Allen had a show).


 
 Doesn't change your position or mine.  

 I had to stop re-greeting people every time I had something to say in a conversation because I got too many odd looks.


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## MrMateoHead

waflet said:


> Hideeho
> My apologies, I left out a very important word in my last post. It should have read "My op was *NOT* meant to be a debate on what amp I need to buy...". That changes the whole sentence completely. My mistake, sorry.
> 
> Yes, Pinnahertz, I know your name, hideeho is my greeting. Like hello, or hi, or hideeho neighbor (although I was saw it LONG before Tim Allen had a show).


 

 Sometimes the best way to learn is to just buy the best (or worst or just cheapest) tube amp you can find and see if you can figure out its contribution (or distortion) to the music you like. Then spend more money on different tubes seeing if you can hear a difference between them.
  
 You can try to be an electrical engineer and decide, based on facts and theory, ahead of time, how things should sound. Or you can just go straight to the "play" phase. I suggest you do. Just understand that planers are less reactive to output impedance than dynamic headphones. They may not "color" as obviously via high-impedance outputs. A cheaper way to color the sound would be to just pick some random EQ curves and apply them. You won't get the even-order distortion of tube amps, but you will familiarize yourself with how different "shapes" sound.
  
 Recently I got tired of reading reviews of speakers and trying to understand measurement techniques since they vary. So I bought a $15 measurement mic, an Android App, and wasted hours of my life seeing how my measurements stood up to published data. It has been rewarding as I am coming to understand the process better, and interpret the results. To make a long story short, it isn't THAT hard to get the basic profile of a speaker nailed down. But any measurement I do will be a lot "noisier" than an anechoic chamber. Period. Turns out one hsa to be pretty creative even when they are trying to be "objective"!


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## bigshot (Sep 6, 2018)

The room is as much of a factor to sound quality as the speaker is, in both good and bad ways. It isn't just a matter of trying to eliminate the sound of the room. If you did that, you'd have an anechoic chamber and no one wants to listen to music in that. The trick is using the sound of the room to its strengths. How the speakers and room relate directly controls how the soundstage and sound location within it work.

An easier way to experiment with the sound of tubes is to just use a regular transparent solid state amp and use a tube emulator DSP. That way you can fine tune exactly the degree and type of coloration you're looking for. There is a good thread on that in this forum.


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## Steve999 (Nov 17, 2018)

This thread has been dormant for too long! And so much of it is waaaaaaaaaaaaaaay over my head. So let me bring things back down to earth.

I have this portable headphone amp. I think it cost me $245. It was some number of years ago. I don't think for a moment it's worth its value in parts. They told me they put some of the stuff from the XM6 in it because the delivery time took a little longer than was stated.

They actually answered the phone when I called and told me that there was no audible difference between their XM4, XM5 and XM6! As there are considerable price differences between the three, I thought that was very cool. If it was a sales tactic they bamboozled me for sure.

But the XM5 ticked ALL of the boxes for me--impedance switch, so I could drive low impedance or high impedance headphones; bass boost and treble boost buttons for when I am listening at low volumes or to anemic headphones; variable crossfeed so I don't get freaked out when I listen to Sgt. Peppers; a +10db gain button for when headphones are particularly hard to drive; and the ability to use it as a DAC with a computer or as an analog amp. Portable, rechargeable or works on mains power or normal batteries. I am using it as a DAC with my computer plus as a headphone amp right now. I've snipped the specifications and the purported measurements below. So I am just asking a generalist question, what does anyone see here? Good, bad, unusual, preposterous? Are the internal components pretty cool? Is there anything to be learned here?

I can tell you it works and you can drop it on the floor a few times and it still works.

Sometimes I want something, and I know it's not worth it's price in parts, but it's _exactly_ what I wanted. So that's what this was.

I am doing snips instead of links so you don't have to click to review the information and so I'm not being a shill for the manufacturer. I won't even show you a picture. I'll just say I got the slicker looking black version for no extra cost for some reason or other. It was a few years back at least.


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## bigshot (Nov 20, 2018)

Features, build quality, and convenience are the best reasons to choose one home audio component over another. Sound quality isn't a good reason because any DAC designed to perform to spec should be audibly transparent. Sound quality is a big issue with transducers.


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## JustASnack

This may seem a bit silly, but I'm not really sure if using my high-gain switch is affecting the way my music sounds (aside from obviously making the signal louder). Unfortunately blind AB testing is very impractical, since using the switch instantly increases/lowers the volume, without giving me time to volume-match the high and low settings. I'm using a Burson Soloist SL MKII

According to the amplifier's manual on page 5, switching from low to high gain increases the headphone amp output from 0.18W to 2W. My question is, does switching from low to high gain affect the way my music will sound if I listen to it at the same volume on both gain settings? When I switch to high gain for example, it always feels like there is better treble and bass response, though obviously it's not a fair judgement, since the music gets noticeably louder when switching, before I have enough time to adjust the volume knob accordingly.
If it helps, my daily drivers are currently the DT 1990 Pro, which have an impedance of 250Ohms and a sensitivity of 102 db SPL (1mW / 500Hz). Also the amplifier is rated at 2.5W @ 16Ohms, with an output impedance of 3Ohms @ 1W. I'm not sure if these specs matter to my question. Truth be told I've tried to understand how this stuff works so many times, but I just can't wrap my head around this kind of stuff. Physics was never my strong point


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## 71 dB

JustASnack said:


> This may seem a bit silly, but I'm not really sure if using my high-gain switch is affecting the way my music sounds (aside from obviously making the signal louder). Unfortunately blind AB testing is very impractical, since using the switch instantly increases/lowers the volume, without giving me time to volume-match the high and low settings. I'm using a Burson Soloist SL MKII
> 
> According to the amplifier's manual on page 5, switching from low to high gain increases the headphone amp output from 0.18W to 2W. My question is, does switching from low to high gain affect the way my music will sound if I listen to it at the same volume on both gain settings? When I switch to high gain for example, it always feels like there is better treble and bass response, though obviously it's not a fair judgement, since the music gets noticeably louder when switching, before I have enough time to adjust the volume knob accordingly.
> If it helps, my daily drivers are currently the DT 1990 Pro, which have an impedance of 250Ohms and a sensitivity of 102 db SPL (1mW / 500Hz). Also the amplifier is rated at 2.5W @ 16Ohms, with an output impedance of 3Ohms @ 1W. I'm not sure if these specs matter to my question. Truth be told I've tried to understand how this stuff works so many times, but I just can't wrap my head around this kind of stuff. Physics was never my strong point



The setting should not affect the sound. The trick is to have equal levels. There is a 10.5 dB level difference and if you don't correct that precisely, the louder setting is likely to sound better. The setting doesn't affect the power, just how loud the sound is for given volume knob setting. So, with very low sensitivity headphones you may want to use high gain setting to avoif having to crank the volume to "eleven."


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## JustASnack

71 dB said:


> The setting should not affect the sound. The trick is to have equal levels. There is a 10.5 dB level difference and if you don't correct that precisely, the louder setting is likely to sound better. The setting doesn't affect the power, just how loud the sound is for given volume knob setting. So, with very low sensitivity headphones you may want to use high gain setting to avoif having to crank the volume to "eleven."


Thanks for your reply! With what you've said in mind, is the reason some people describe certain headphones as sounding better when driven balanced because balanced can drive headphones louder? Or can balanced outputs drive certain headphones "to their fullest potential" when single ended can't, given we're driving the same headphones at the same volume from both outputs?


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## StandsOnFeet

JustASnack said:


> some people describe certain headphones as sounding better when driven balanced


Some people will claim that the system sounds better when they replace their volume knob with an expensive one made of rare wood. Being skeptical of any claim that isn't supported by blind testing seems like a sound plan.


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## castleofargh (Apr 23, 2019)

JustASnack said:


> Thanks for your reply! With what you've said in mind, is the reason some people describe certain headphones as sounding better when driven balanced because balanced can drive headphones louder? Or can balanced outputs drive certain headphones "to their fullest potential" when single ended can't, given we're driving the same headphones at the same volume from both outputs?


 balanced outputs, not always but very commonly have double the impedance and voltage. the difference in listening level alone is enough to invalidate any impressions they get. then you add the delay caused by having to switch the cables so users usually won't have the ability to rapidly switch between the 2 options. that's another red flag as far as listening tests are concerned. and as cherry on the cake, I'd say that the effort to get a balanced amp, and often purchase balanced cables for our headphone, is already the action of somebody who wishes and expects the balanced setup to sound different/better. so if it wasn't already obvious, people's impressions about this shouldn't be taken at face value.

as for the old question of SE vs balanced. until I see decisive evidence of the contrary, I'm of the opinion that it's a false dichotomy. good amps do not happen to all be SE or all be balanced. amps designed to nominally drive your headphone load at your desired level aren't all SE or all BA. some amps will do the job, some amps are crap or simply designed for a different range of loads and gains. those are relevant variables, along maybe with some concerns for basic fidelity.


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## E1DA

I have two HPAs, one with 1.5ohm output impedance, second with 50 mOhm, and I easily hear the difference in bass there. 1.5ohm has a bit less control but noticeable more punch vs 50mOhm. It is quite normal for the 4-8ohm speakers if less damping induces some hump on the frequency response but I use a planar headphone with perfectly flat impedance vs frequency. That's a bit confusing to me..


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## bigshot

You should make sure your impedance is matched properly. Then everything will sound correct and you won't run into imbalances like that.


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## castleofargh

E1DA said:


> I have two HPAs, one with 1.5ohm output impedance, second with 50 mOhm, and I easily hear the difference in bass there. 1.5ohm has a bit less control but noticeable more punch vs 50mOhm. It is quite normal for the 4-8ohm speakers if less damping induces some hump on the frequency response but I use a planar headphone with perfectly flat impedance vs frequency. That's a bit confusing to me..


with such a small impedance variation on a planar, I really doubt that it's the cause for what you feel in the low end. with impedance we always have as you mention some typical bass hump where the impedance rises most on the headphone/speaker(common for dynamic drivers). we have some usually inconsequential low freq roll off with low impedance loads(could become audible at some point, or really obvious when caps at the output join the headphone to form a high pass filter). when the damping ratio is horrendous, we end up hearing what's IMO just bad mechanical damping after the electrical damping has become bad enough. it's something we can also experience with big speaker drivers, but with headphones my personal experience is that it's pretty hard to create such circumstance because headphones tend to be pretty tight on their own. plus the typical impedance is much higher than that of speakers. 
so I would suspect other reasons due to design for audible difference in the low end in your case, and the difference in output impedance to be mostly or completely unrelated to how they sound.


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## bigshot

Which one is transparent and which one isn't then?


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## E1DA

castleofargh, you could be right again. These two design is completely different for topology reason, first is open loop Power DAC(PowerDAC V2 = TAS5558 I2S->PWM and lots of LVC logic gates in parallel as a PWM power stage + passive LC demodulation), the second one is conventional DAC+AMP(#9038S = ES9038Q2M+ AD8397 power stage). Both using a USB 5V as a power rail without extra regulation, just as is, with lots of capacitors with few milliohms ESR. For sure in the first case, just due to the system has no feedback at all, all 5V regulation dynamics goes directly to the output, of course, it is smoothed by 5000uF 5mOhm solid-polymer caps but not up to the bottom end,  simply no room for 20000uF, actually, USB will fail to start with >5000uF. In the case of AD8397 output stage, the system has a lot of loop gain targeted to correct 5V rail disturbances, and finally, THD+N vs frequency is perfectly flat. The PowerDAC has higher THD+N in low freqs, with about 100-200Hz corner, depends on the load impedance. BTW, 1 year ago I worked with proto of Power DAC amp 125W*2ch 4ohm, where I can bypass a noise-shaper in one single click i.e. the system could operate in the one of modes 1-open loop(no feedback)/2-closed loop(tonnes of feedback). And the situation is reproduced in the same manner as I have with headphones PowerDAC V2 and #9038S:
1) Open loop mode sounds more punchy in bass and kinda softer, bass less controlled but pleasantly
2) Closed loop mode has a lot less THD+N and much better SNR, bass sounds tight and a bit dry vs Open loop mode
1 year ago I explained that phenomenon by damping factor difference and complex speaker impedance nature but today I have the same with planar headphones 
 In my opinion, the open loop system sounds more pleasant(kind of more freely) but a bit less accurate in basses. In highs, both PowerDAC V2 and #9038S, sounds razor-detailed with no any smoothy unlike cheap HPA on TI chips like TPA6130(THD 6kHz is 10x times higher than 1kHz i.e. the different amount of loop gain applied withing audio-band. As claimed B. Putzeys this is the common reason for coloration in highs. It sounds like treble knob tuned down for -3-6db).


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## castleofargh

you're suggesting that I've had good ideas twice in 2019 already. now I know this is my year!!!!! ^_^


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## E1DA

Ideas made us a human.


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## maziarshaghaghi

*do you know that the impedance sometimes matter but sometimes not?
because the lowest headphone impedance is 8 ohms & the highest headphone impedance is 600 ohms and if you calculate them u can see that the difference is 75 in ohms or mW, so the voltage is more than 8 and less than 9 V rms

8^2=64, 9^2=81

so don't worry about the high impedance, i know that the higher impedance decreases the volume and needs more voltages but the highest impedance will decreases less than 19 dB volume

if u have no problem with the highest impedance u can find some noise cancellation headphones that have more than 600 ohms active impedance & u can measure what the difference is.*


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## FourT6and2

Informative thread. So how does one intelligently demo headphones? For example in a store. Let's say I'm comparing 3 different headphones in a store to decide which one to buy. But I'm using the same amp with all three. Amp's output impedance is... oh let's say 16ohms. Headphone 1 is 300ohm, Headphone 2 is 80ohm, and Headphone 3 is 36ohm. I would be better off using an amp with as low of an impedance as possible it seems. Let's through one more monkey wrench in there: amp power. amp with 16ohm output impedance can pump out 5 watts and is powered by mains/wall. There's another amp available, but it's battery powered and only puts out (35mW at 600ohm), but its output impedance is less than 1ohm. It's a fraction of an ohm.

So... what do?

Also, let's say I want to buy a quality planar magnetic headphone with a listed impedance of like 30-50ohms. And let's say my requirements for an amp are built-in DAC, balanced output (either 4-pin XLR or 4.4mm Pentaconn), and enough wattage to really get the job done. There aren't a lot of options out there it seems. Many headphone amp with DACs just don't have the wattage or their impedances are too high.


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## bigshot

The best way to compare headphones is with the proper impedance matching. You find the cans with the sound you want, and you build your system around that. However, that might not apply to portable rigs. You need to balance sound with convenience. People don't value convenience as much as they should. Hauling around a pile of black boxes and maintaining battery power in all of them is a pain. It might be better to sacrifice a tiny bit of sound quality in favor of simplicity.


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## Àedhàn Cassiel

Is there any truth to the notion that electrostatic "energizers" matter more than regular old headphone amps? People that admit the differences between regular amps are tiny often still think the differences between "energizers" matter a lot. I have an SRM-006t tube "energizer" that pairs with a SR-404 from Stax, and I've been told I shouldn't try the SR-007 out on it at all because it will just totally _totally _screw up the sound apparently. The SR-007 impedance is 170k ohms at 10kHz. Sensitivity 100dB/100V RMS at 1kHz. I can't find anything on the stats of the SRM-006t though.


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## pinnahertz

Àedhàn Cassiel said:


> Is there any truth to the notion that electrostatic "energizers" matter more than regular old headphone amps? People that admit the differences between regular amps are tiny often still think the differences between "energizers" matter a lot. I have an SRM-006t tube "energizer" that pairs with a SR-404 from Stax, and I've been told I shouldn't try the SR-007 out on it at all because it will just totally _totally _screw up the sound apparently. The SR-007 impedance is 170k ohms at 10kHz. Sensitivity 100dB/100V RMS at 1kHz. I can't find anything on the stats of the SRM-006t though.


The SRM-006TS specs are *here.*

On one hand it doesn't appear that it would cause a problem driving the SR-007, certainly no damage would occur.  As to "I've been told.....totally screw up the sound"....yeah, well who told you and why would you believe them? Are you here looking for a contrary opinion from someone equally uncredited and unqualified?  How is that going to help anything?  Why don't you just give it a try?  

On the other hand, electrostatic headphones and the manufacturer's recommended driver are something I've always considered a closed system, especially within a particular brand. If you want different sound from the same headphones, then use actual equalization rather than messing with un-verified, un-documented, and un-predictable combinations.  At least you'll know what you're getting, be able to document it, refine your settings, and progress forward.


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## Àedhàn Cassiel

My only way for me to try an SR-007 is by shelling 1400 out up front for a used pair. I was considering that, til someone warned me.


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## pinnahertz

Àedhàn Cassiel said:


> My only way for me to try an SR-007 is by shelling 1400 out up front for a used pair. I was considering that, til someone warned me.


Why try an SR-007 in the first place?  Who warned you not to?  I would analyze my goals.  What am I trying to achieve? Obviously "better", but there are many paths to "better" besides another electrostatic, recommendations either way not withstanding.  Done the DSP/EQ thing yet?  It's like painting with a limitless palette vs buying a different ($1400) paint and using the same brush.

If you bought a used pair and hated it, you can resell your used pair and recover most of the outlay.  Then you'd know if your warning was valid, and more importantly, you'd be the expert and we could all ask you!


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## Àedhàn Cassiel (Mar 20, 2020)

I've played around a lot with EQ over the last couple years, and have a good system down now for eliminating any troublesome peaks from new headphones. I tune my HD800 towards but not all the way to the Harman curve. I love the RAD-0 with no EQ, the Verite Closed needs a bit to reduce upper-mid shout with extreme metal.

I am inclined to agree that the only difference between different headphones is signature and distortion, but I think there are limits to how far digital EQ can take you, (1) because it gradually adds distortion and (2) because software just can't give you the number of taps you need running to truly take things to the next level - the studies emulating one headphone on another use dedicated DSP hardware running hundreds of taps, 200 is on the low end. So for a non-expert not planning to dump a hundred hours in, cutting troubling peaks, maybe throwing in a bass boost option is the most realistic use for EQ IMO. 

I see an SR007 that's been going for sale here for a long while, looks like they aren't in high demand on the used market. Most people after that sound already flew to Japan and picked up a fresh pair, very few used buyers are looking there for Stax. I could easily get stuck with them and I'm already embarassed by the amount of money I have in headphones haha


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## pinnahertz

Àedhàn Cassiel said:


> I've played around a lot with EQ over the last couple years, and have a good system down now for eliminating any troublesome peaks from new headphones. I tune my HD800 towards but not all the way to the Harman curve. I love the RAD-0 with no EQ, the Verite Closed needs a bit to reduce upper-mid shout with extreme metal.
> 
> I am inclined to agree that the only difference between different headphones is signature and distortion,


Those are not small.  Add to them the method of delivery: closed, open, IEM...all very different.


Àedhàn Cassiel said:


> but I think there are limits to how far digital EQ can take you, (1) because it gradually adds distortion and (2) because software just can't give you the number of taps you need running to truly take things to the next level - the studies emulating one headphone on another use dedicated DSP hardware running hundreds of taps, 200 is on the low end. So for a non-expert not planning to dump a hundred hours in, cutting troubling peaks, maybe throwing in a bass boost option is the most realistic use for EQ IMO.


Depends on the type of EQ.  IIR-based EQ, sure, FIR not so much.  The number of "taps" doesn't describe a real limit though.  The real limits to EQ are how the curve is developed.  You can use others measurements, your own measurements, or subjective judgement. All have issues with precision.  Measurements and DSP that result in inverse FIR with target curve are limited only by the precision of the measurements, not filter complexity.   However, there is also a practical limit based on audible change too.  Lots of tiny corrections make for a complex filter with no audible effect.  And if you alter the measurement setup even slightly, all those tiny excursions will change too, so you effectively need a cluster and logical means of combining them.  An average is ok if you take a lot of measurements, something like fuzzy clustering would be better.  Smoothing is appropriate in any case.  Regardless, you don't need a complex filter to deal with the audible issues.   And you can't EQ a change in headphone/ear coupling because you can't EQ more than one arrival angle from the driver to the ear.  


Àedhàn Cassiel said:


> I see an SR007 that's been going for sale here for a long while, looks like they aren't in high demand on the used market. Most people after that sound already flew to Japan and picked up a fresh pair, very few used buyers are looking there for Stax. I could easily get stuck with them and I'm already embarassed by the amount of money I have in headphones haha


I'm still not understanding what your goal is.  I don't consider a used equipment purchase as being "stuck" with anything, if the purchase price is at or below market value. It's more like a rental or free loan.


----------



## bigshot

I have no complaints about the ability of digital EQ to correct cans. Digital EQs add no audible distortion, and a good parametric EQ can do pretty much anything that needs doing. It's not like decent headphones are that far off target. They usually just need a little tweak here and there. I'm lucky because my headphones are designed to not need EQ nor amplification. My major gripe against EQ is one of convenience, not quality.


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## Àedhàn Cassiel (Mar 20, 2020)

bigshot said:


> I'm lucky because my headphones are designed to not need EQ nor amplification.



What headphones do you use?



> I'm still not understanding what your goal is.



It's really neither here nor there, as far as establishing if there's a scientific answer to the question is concerned. I'm not sure why I should submit to probing over my personal purchase decisions at all, but especially if no one's sure about the answer to the question anyway  I don't plan to make the leap unless I can find some objective knowledge to assure me this wouldn't _actually _be a "bad pairing" and that's that


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## pinnahertz

Àedhàn Cassiel said:


> It's really neither here nor there, as far as establishing if there's a scientific answer to the question is concerned.


Understanding the goal would result in better information return.  The goal was not initially stated clearly, it was vague, so the information you got is also vague and general, with opinion thrown in.


Àedhàn Cassiel said:


> I'm not sure why I should submit to probing over my personal purchase decisions at all, but especially if no one's sure about the answer to the question anyway  I don't plan to make the leap unless I can find some objective knowledge to assure me this wouldn't _actually _be a "bad pairing" and that's that


Probing was to try to extract more information so the response would be more useful.  If you go to the doctor and say "I don't feel good", he's going to probe a lot more in order to prescribe a remedy or treatment. 

"Good" and "Bad" are relative here.  It's a non-destructive combination, and I see no reason (other than possibly manufacturer's recommendation) that the old driver box wouldn't work.  You did clarify your goal somewhat by stating that you already own the older box.  That makes your goal of owning and using the SR007 and driving them at the lowest possibly cost more obvious.  However, the strong reverse bias of "don't even bother" from the mythical other authority is a lot to counter with either logic or science.


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## bigshot (Mar 21, 2020)

Àedhàn Cassiel said:


> What headphones do you use?



Oppo PM-1



pinnahertz said:


> Understanding the goal would result in better information return.



Bingo. Random information yields random results. You have to define your criteria.


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## Nettlesomeness

I salute you proton007, great explanation and specifically at the beginning with the pipes example. The rest is something I'm sorta ashamed that I couldn't digest fully, will be coming back to this informative post again.


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## gooeyrich (Jun 25, 2020)

Gentleman, can anyone clarify what is sufficient power to get the Beyer 600 ohm cans to their full potential? We've been having a discussion in the last few pages of this thread regarding the matter for reference: https://www.head-fi.org/threads/the-beyerdynamic-dt880-discussion-thread.429371/page-780


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## Chris Kaoss (Jun 25, 2020)

Hi.
100mW to 300mW at 13 volts are a good point to start with.
The higher the volts the better.
Voltage is key on higher ohms, not only the raw power.


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## castleofargh

gooeyrich said:


> Gentleman, can anyone clarify what is sufficient power to get the Beyer 600 ohm cans to their full potential? We've been having a discussion in the last few pages of this thread regarding the matter for reference: https://www.head-fi.org/threads/the-beyerdynamic-dt880-discussion-thread.429371/page-780


Based on this https://www.innerfidelity.com/images/BeyerdynamicDT880600ohm.pdf , you'd get the usual upper target of 115dB SPL with about 9V or 140mW.
Tyll's pair at the time seemed to give him 93.6dB/mW.


On beyer's site you find this explanation of their lacking specs:


> The power handling capacity refers to the electrical power that can be supplied to the headphones/loudspeaker without causing damage to them.
> Important: While the maximum power handling capacity designates the maximum power that can be supplied to the product for a short time, the nominal power handling capacity describes the maximum power that will be tolerated by the product, even when permanently operating.


So with the 880 600ohm version apparently given as:
  Nominal SPL  . . . . . . . . . . . . . . . . . . 96 dB
Power handling capacity. . . . . . . . . . 100 mW

And innerfidelity's values, you would want to avoid going beyond around 113.5dB SPL with them.
I have no idea how reliable those measurements or specs are. And of course that 100mW limit, if accurate, doesn't mean you can't go and get amps with a much much higher maximum output into 600ohm. Just don't let kids play with the volume ^_^.


----------



## gooeyrich

Chris Kaoss said:


> Hi.
> 100mW to 300mW at 13 volts are a good point to start with.
> The higher the volts the better.
> Voltage is key on higher ohms, not only the raw power.





castleofargh said:


> Based on this https://www.innerfidelity.com/images/BeyerdynamicDT880600ohm.pdf , you'd get the usual upper target of 115dB SPL with about 9V or 140mW.
> Tyll's pair at the time seemed to give him 93.6dB/mW.
> 
> 
> ...



Thank you for the feedback, do you think the Atom is sufficient? I can't seem to find the voltage on the specs:

https://jdslabs.com/product/atom-amp/


----------



## SoundAndMotion

gooeyrich said:


> Thank you for the feedback, do you think the Atom is sufficient? I can't seem to find the voltage on the specs:
> 
> https://jdslabs.com/product/atom-amp/


Yes:


----------



## Chris Kaoss

gooeyrich said:


> Thank you for the feedback, do you think the Atom is sufficient? I can't seem to find the voltage on the specs:
> 
> https://jdslabs.com/product/atom-amp/


Not really, imo.
The specs mentioned by SoundandMotion are the max output specs.
I'd recommend higher than 10volts for such a high impedance headphone.

As i stated for the T1, the impedance of the dynamic driver got a hugh swing on certain frequencies.
For the T1, it rises up to nearly 1300ohm between 50Hz and 110Hz.
As you can see on the paper from innerfidelity, the 880 600 rises up to 750ohm.
So these are the specs you should calculate with.

A nice quote from RAA:
"
The resistance affects the amount of current that the amplifier should give to the headphones. If the current is not enough, the sound quality will deteriorate, beginning with harsh in the sound and ending with a crackling. In most cases, at low current values, the amplifiers operate in comparable quality to class A, and as the current level rises, the quality decreases toward AB, B, and the clipping zone.

Imagine that you have a water tank, which gradually fills with water. The voltage from the amplifier this is the pressure with which the pump draws water from the reservoir. If the inflow of water in the tank is lower than the volume that the pump pumps out, then at the pump outlet we collect water and "bubbles". Similarly will be with the sound from the headphones, which are lacked the current from the amplifier."
[Quote off]


----------



## castleofargh

Chris Kaoss said:


> Not really, imo.
> The specs mentioned by SoundandMotion are the max output specs.
> I'd recommend higher than 10volts for such a high impedance headphone.
> 
> ...


I don't agree with that. As a user you will set your listening level based mostly on the midrange. Once 1 or 2kHz is set to have a given output to deliver a given loudness into the headphone, everything else will be a function of that one setting. In this context the variation at 80Hz of about 100ohm compared to 1kHz should be irrelevant with a low impedance amplifier giving very high damping at all frequencies. 

On the other hand, there are many arguments in favor of having a good deal of headroom power/gain for the headphones, some legit(room for replay gain, EQ, less than 2V DAC, etc) but the amount needed is arguable as it often depends on user's habits who would have decided on a different max output target in the first place. Some arguments are legit but highly dependent on the type of amp used(IMO not relevant on that particular amp). And some are just audiophile misconceptions about power actually going into a load. In any case, many people would not be satisfied with an amplifier that just barely hits the highest output they had set as their target(again for good or bad reasons). In that respect I can somehow understand your concern for some users, but the 700+ohm thingy doesn't matter IMO.


----------



## Chris Kaoss

Yes, i'd agree.
But the imp curve of the 880 isn't just that one hump at around 80Hz.
Maybe my bias with the hugh impedance hump of the T1 kicks in a bit. ^^
Sounds even better with an amp that maxed out at 19volts, for example.
Of course, that's my experience with.


----------



## bigshot

Sometimes more isn't better. Sometimes it's just more.


----------



## magicscreen

gooeyrich said:


> Thank you for the feedback, do you think the Atom is sufficient?


The Atom cannot drive a Sennheiser HD6XX properly and that is only 300 ohm.


----------



## gooeyrich

magicscreen said:


> The Atom cannot drive a Sennheiser HD6XX properly and that is only 300 ohm.



Based on what?

https://www.audiosciencereview.com/...e-amplifier-to-drive-600-ohm-headphones.6910/


----------



## theaudiologist1

hey guys. I have an ATH-R70x paired with an RHA DACAMP L1. My R70x's are 470 with a sensitivity of 98 or 99dB/mW (my box says 98 but everywhere else even AT's website says 99 :/), and my DACAMP L1, well, RHA has given NO DATA on the impedance and voltage. The only info they gave was that it outputs 300mW@16Ohms and 28mW@300Ohms. Idk how much it outputs at 470Ohms if somebody does the math please let me know. 

Regardless, my DAC handles the quite well with PCM and gets very loud even with classical. With DSD it becomes somewhat quieter when listening to the quiet parts of a classical recording. I just want to know what should be the max loudness for a headphone to sound good with quiet and very dynamic music like in parts of a concerto? From my DAC specs, my DAC can push the R70x to a maximum of 112-113dB. I heard an orchestra at full force is 120dB so am I missing some details? Also is there a software for Mac that helps me determine my DAC's output power, impedance and voltage?


----------



## gooeyrich

*



			JDS Labs Atom
		
Click to expand...

*


> Audibly indistinguishable from Magni Heresy or Geshelli Archel 2 Pro
> 
> Second lowest power output (though ample for most headphones), has the most features here, with an unconventional pre-amp output (see below), dual gain settings and two inputs (1x RCA, 1x 3.5mm TRS), at the joint-lowest price, in a custom, neat, plastic chassis/case.
> 
> The pre-amp output on the Atom appears to be tapped either after the gain stage or from the actual headphone output,* and results in significantly higher voltage outputs than either the Liquid Spark or any version of Magni* (and likely higher noise - though still below audible levels). This higher voltage output from the pre-amp outputs may result in more limited volume control range and/or input level headroom issues with some consumer amplifiers or active speakers.



https://www.headphones.com/blogs/ne...-heresy-headphone-amplifier-review-comparison

I always read that voltage is what matters with high impedance headphones?


----------



## gooeyrich

Also dropping this here for additional info/reference:

https://www.headphonesty.com/2019/04/headphone-impedance-demystified/


----------



## gooeyrich




----------



## KeithPhantom

gooeyrich said:


> I always read that voltage is what matters with high impedance headphones?


Both current and potential are important for high and low impedance headphones. You also have to factor out sensitivity/efficiency (related but not the same). High impedance headphones are less sensitive to imperfection in the amplifying and source stages, also are less of a load to an amplifier (it is easier to supply voltage than current). Actually, low impedance headphones are *more* of a load to an amplifier, but it happens that portable gear has really high efficiency/sensitivity values which let them reach higher volume at a single mW (and being low sensitivity they don't need as much voltage). I also have to add that you need way more power to power lower sensitivity headphones, almost regardless of the impedance presented.


----------



## dazzerfong (Jul 28, 2020)

High impedance, high sensitivity: low voltage, low current
High impedance, low sensitivity: high voltage, low current
Low impedance, high sensitivity: low voltage, high current
Low impedance, low sensitivity: high voltage, high current

Power requirements are determined from your sensitivity/efficiency. The distribution between voltage and current is determined by your impedance. That's why whenever people say high impedance headphones need more power, I roll my eyes.


----------



## Chris Kaoss

Yes.
But it's like computer specs, there's a "minimum requirements", which drives them "well", and "recommended ones", which will have a small impact.


----------



## KeithPhantom

Chris Kaoss said:


> "recommended ones", which will have a small impact.


If you're able to reproduce the highest peaks of your chosen SPL within a power value, that's enough power for the transducer.


----------



## jotaku

OK so maybe I haven't spelunk' d the forums enough (but I think this is the right thread for this discussion this time), but I have never found an answer that even remotely satisfied me concerning this topic.

So I have a degree in electrical engineering. One of the classes I took was about transmission lines and the importance of matching your output and your load impedances. The grossly simplified version being the following:

When you match impedance from your source (amp; *ZS*) and your load (headphone/speaker; *ZL*) you are just fine._ (According to audio literature, the reactive part of impedance is ignored i.e. the inductive/capacitive part of impedance. So we only care about the resistance i.e. Ohms. Don't know how true this is. I have my doubts.)_
When you have an impedance mismatch you have signal reflections in your transmission lines that cause destructive interference.
I was wondering why no one talks about this when talking about equipment synergy. Is it a non-factor? Does *Dampening Factor* matter more? (*DF = ZL/ZS*) Or is it a large part of it and people don't realize it? 

It seems like when people talk about amps that work well with certain headphones, upon further research these amps have an output impedance closer to the impedance of the those headphones (less reflections/destructive interference). Or maybe it is the result of some magic *DF* ratio, but I didn't look at that closely.

As a slight tangent, signal reflections affect certain frequencies differently; supporting the claim that certain amp/headphone pairings improve certain frequency responses, like improved bass response or extension.

Am I missing something fundamental here? Oversimplifying things?

Just wanting to get my head screwed on straight.


----------



## castleofargh

jotaku said:


> OK so maybe I haven't spelunk' d the forums enough (but I think this is the right thread for this discussion this time), but I have never found an answer that even remotely satisfied me concerning this topic.
> 
> So I have a degree in electrical engineering. One of the classes I took was about transmission lines and the importance of matching your output and your load impedances. The grossly simplified version being the following:
> 
> ...


I'm going to do the captain obvious part. With impedance bridging design we don't need a different amplifier anytime we use a headphone with a different impedance.

About transmission line. We're dealing with short cables and most of all, audio frequencies. Digital interconnects go at higher frequencies and do use impedance matching(even for the cables). It's just not necessary at audio freqs. As far as I understand that's really the key point here.

About your potential correlation between sound preference and impedance matching. The scenario of 2 amps with vastly different impedance outputs, usually carries many variables changing along with the amps. In practice, maybe one amp would be 0.3ohm SS amp with a ton of negative feedback, while the other amp would most likely be some old tube amp design if we're looking for 100ohm or more. That makes observation not so conclusive about one single cause. And that's assuming the listeners even bothered to properly volume match the amps, and used blind testing. As that almost never happens, the existing testimonies should be taken with a grain of salt.

But there is no doubt that the impedance change at the amp could lead to audible changes with some headphones. Starting with good old frequency response. We can expect the amplitude in the subs to change a little. Also the typical impedance bump at the main resonant frequency of the transducer, would boost that freq with the high impedance amp. Then is the total damping of the transducer that might perhaps be audible in some cases, but I haven't seen much in term of demonstrating an audible impact on headphones. I've seen something regarding fairly massive sub-woofers once, but it's likely that the impact is much smaller for tiny very light transducers with an already high mechanical damping. Whereas the frequency response change from change in the impedance ratio, is something that will easily be audible as soon as it reaches big enough amplitude. And that impact has been confirmed several times. You just have to add resistors in series between the amp and the headphone so get frequency response change. 
So until I see supporting evidence for the rest, I'm tempted to assume that FR variations, and just 2 amps being 2 different amps, are the lead causes for perceived changes. That and of course, audiophiles hearing a lot of stuff with their eyes and wallet.😈


----------



## 71 dB

jotaku said:


> So I have a degree in electrical engineering. One of the classes I took was about transmission lines and the importance of matching your output and your load impedances. The grossly simplified version being the following:
> 
> When you match impedance from your source (amp; *ZS*) and your load (headphone/speaker; *ZL*) you are just fine._ (According to audio literature, the reactive part of impedance is ignored i.e. the inductive/capacitive part of impedance. So we only care about the resistance i.e. Ohms. Don't know how true this is. I have my doubts.)_
> When you have an impedance mismatch you have signal reflections in your transmission lines that cause destructive interference.
> ...



Impedance matching in transmission lines applies only when the transmission line is so long compared to the wavelength of the signal, that the voltage level at the ends of that transmission line differ from each other. At _audio frequencies_ this means the transmission lines (signal speed about 2/3 of the light speed or 200.000 km/s) must be kilometers/miles long. This is why audio cables don't require (thank God!) impedance matching. The frequencies are low enough. The reflections are nearly _identical_ with the signal and destructive interference doesn't really happen. At 20 kHz, just one full cycle of electrical signal in an audio cable would be 10 km (6 miles) long! Having cable length of 1 % of one cycle makes the reflections are nearly _identical. _That's 100 m (~300 feet) of cable and that's for 20 kHz, which older people can't even hear! 

Damping factor does matter, because it affects sound quality. The higher damping factor the more faithful the resulting sound is to the original signal, but one can of course reduce damping factor by increasing source resistance to have less faithful, but perhaps more relaxed sound.

Some headphones are mechanically damped so much they don't really need electrical damping meaning the damping factor can be poor. Typically these headphones also have very flat impedance curve (impedance is almost the same on all frequencies). This means high source impedance won't affect the frequency responce much. Some other headphones have very little mechanical damping and need electrical damping (low source impedance). Typically this kind of headphones have a very curvy impedance curve and a huge bump on the resonance frequency of the driver (around 100 Hz or so). If these headphones are driven from sources with high output impedance the result is not only inadequate damping, but even more seriously a poor frequency response with a bump on the  driver element resonance frequency.


----------



## jotaku

71 dB said:


> Impedance matching in transmission lines applies only when the transmission line is so long compared to the wavelength of the signal, that the voltage level at the ends of that transmission line differ from each other. At _audio frequencies_ this means the transmission lines (signal speed about 2/3 of the light speed or 200.000 km/s) must be kilometers/miles long. This is why audio cables don't require (thank God!) impedance matching. The frequencies are low enough. The reflections are nearly _identical_ with the signal and destructive interference doesn't really happen. At 20 kHz, just one full cycle of electrical signal in an audio cable would be 10 km (6 miles) long! Having cable length of 1 % of one cycle makes the reflections are nearly _identical. _That's 100 m (~300 feet) of cable and that's for 20 kHz, which older people can't even hear!
> 
> Damping factor does matter, because it affects sound quality. The higher damping factor the more faithful the resulting sound is to the original signal, but one can of course reduce damping factor by increasing source resistance to have less faithful, but perhaps more relaxed sound.
> 
> Some headphones are mechanically damped so much they don't really need electrical damping meaning the damping factor can be poor. Typically these headphones also have very flat impedance curve (impedance is almost the same on all frequencies). This means high source impedance won't affect the frequency responce much. Some other headphones have very little mechanical damping and need electrical damping (low source impedance). Typically this kind of headphones have a very curvy impedance curve and a huge bump on the resonance frequency of the driver (around 100 Hz or so). If these headphones are driven from sources with high output impedance the result is not only inadequate damping, but even more seriously a poor frequency response with a bump on the  driver element resonance frequency.


Thanks everyone for contributing to answer my question. I just found this article from sound on sound that makes a lot of sense coupled with everything people have said.
https://www.soundonsound.com/techniques/understanding-impedance


----------



## redrol

I read that a general rule of thumb is the driver impedance should be around 8x the amplifier impedance.  Sounds reasonable from what I know.  Is this a decent idea?


----------



## 71 dB

redrol said:


> I read that a general rule of thumb is the driver impedance should be around 8x the amplifier impedance.  Sounds reasonable from what I know.  Is this a decent idea?



Actually this is not a very good rule of thumb, because it all comes down to how much mechanical damping the driver has got on its own. Drivers with a lot of mechanical damping work well even when the driver impedance is less than 8x the amp output impedance while some headphones have for sensitivity reasons so little mechanical damping that even 8x ratio of impedances isn't enough. I think in the past headphones where less sensitive in general (not designed to work with portable devices) and they had generally enough mechanical damping for the 8x rule to make sense, but the World has changed and headphones of today can be quite sensitive (have very little mechanical damping meaning they require electrical damping which means very low amp output impedance). For this reason the 8x rule should be updated and I suggest to make it a 20x rule if we insist on having one. However, I think a better way to deal with this amp output impedance issue it to divide headphones into two categories:

1. High mechanical damping models (measured impedance curve is very flat) => Amp output impedance can be pretty high.
2. Low mechanical damping models (measured impedance curve is not flat) => Amp output impedance should be very low.

Even when mechanical damping is high, the voice coil inductance causes the impedance to rise at highest frequences. In order to avoid frequency response error bigger than 0.5 dB, the output impedance Zout of the amp should be at most:

Zout ≤ Zmax × Zmin × (𝛃 - 1) ÷ (Zmax - 𝛃 × Zmin),

where Zmax and Zmin are the maximum and minimum impedance values and 𝛃 = 10^(0.5/20) ≈ 1.06 is defined by the maximum allowed frequency response error. If we plot the maximum allowed amp output impedance as a function of Zmax/Zmin ratio, we get a graph like this:


----------



## redrol

OH wow.  I dunno why I never get notifications for these threads.  THANK YOU @71 dB 

I fully understand now.


----------



## 71 dB

redrol said:


> OH wow.  I dunno why I never get notifications for these threads.  THANK YOU @71 dB
> 
> I fully understand now.


You are welcome @redrol  
I'm glad I could help.


----------



## redrol

Yeah, I am now over here doing the maths on my expensive low impedance IEMs with wacky impedance curves to match.  Much appreicated!!  I am telling all my buddies because this is more important than DACs and other stupid things people spend money on.


----------



## Chris Kaoss

71 dB said:


> Actually this is not a very good rule of thumb, because it all comes down to how much mechanical damping the driver has got on its own. Drivers with a lot of mechanical damping work well even when the driver impedance is less than 8x the amp output impedance while some headphones have for sensitivity reasons so little mechanical damping that even 8x ratio of impedances isn't enough. I think in the past headphones where less sensitive in general (not designed to work with portable devices) and they had generally enough mechanical damping for the 8x rule to make sense, but the World has changed and headphones of today can be quite sensitive (have very little mechanical damping meaning they require electrical damping which means very low amp output impedance). For this reason the 8x rule should be updated and I suggest to make it a 20x rule if we insist on having one. However, I think a better way to deal with this amp output impedance issue it to divide headphones into two categories:
> 
> 1. High mechanical damping models (measured impedance curve is very flat) => Amp output impedance can be pretty high.
> 2. Low mechanical damping models (measured impedance curve is not flat) => Amp output impedance should be very low.
> ...


Thanks for heading up with and i do agree with.

Nonetheless, i'm struggling to apply this to the almost flat imp line (curve) of a planar.

Did someone encounter an unusual behaviour with a planar on a higher imp out amp?
Regarding to my Era-1, which is flat on 21 ohm from bottom to top. 

Sadly, i don't have an amp with higher imp out to test it by myself.

Thanks guys.


----------



## 71 dB

Chris Kaoss said:


> Thanks for heading up with and i do agree with.
> 
> Nonetheless, i'm struggling to apply this to the almost flat imp line (curve) of a planar.
> 
> ...


If you mean by struggling to apply this using the equation for the largest allowed output impedance then one needs to notice that it doesn't "work", if the variation of impedance is less than ~6 %. It will give NEGATIVE output impedance for the amp. This is not a problem at all. All it means is the headphone impedance curve is so flat it doesn't matter how high the amp output impedance is, the frequency response error will always be less than 0.5 dB. The only problem with high amp output impedance in these cases such as your 21 Ω cans is that only a small portion of the amp voltage is over the headphone, for example if the amp output impedance was 100 Ω, only ~17 %* of the amp voltage would be over the headphone. This means almost 12 dB attenuation** compared to an amp with 10 Ω output impedance given same amp voltage.

Hopefully this helps in your struggles.
________________________________
* 21 Ω ÷ (100 Ω + 21 Ω) = 0.173355... ≈ 17 %
** 20 × log10( (21 Ω + 10 Ω) ÷ (21 Ω + 100 Ω) ) = 20 × log10(31 ÷ 121) ≈ 11.8 dB


----------



## Chris Kaoss

71 dB said:


> If you mean by struggling to apply this using the equation for the largest allowed output impedance then one needs to notice that it doesn't "work", if the variation of impedance is less than ~6 %. It will give NEGATIVE output impedance for the amp. This is not a problem at all. All it means is the headphone impedance curve is so flat it doesn't matter how high the amp output impedance is, the frequency response error will always be less than 0.5 dB. The only problem with high amp output impedance in these cases such as your 21 Ω cans is that only a small portion of the amp voltage is over the headphone, for example if the amp output impedance was 100 Ω, only ~17 %* of the amp voltage would be over the headphone. This means almost 12 dB attenuation** compared to an amp with 10 Ω output impedance given same amp voltage.
> 
> Hopefully this helps in your struggles.
> ________________________________
> ...


Thank you. 

Got it.
So nothing to worry about if the amp is capable to deliver what's needed. 

I'm perfectly fine with.


----------



## 71 dB

Chris Kaoss said:


> Thank you.
> 
> Got it.
> So nothing to worry about if the amp is capable to deliver what's needed.
> ...


You are welcome. 

Yes, owners of headphones with ultra-flat (varies less than 6 %) impedance curve should worry only about the power and if that's in order too then happy listening!


----------



## redrol

How about a 6ohm set (@ 1000hz) with dips below 2ohm for the low BAs?


----------



## redrol

Here is said set with different OIs:


----------



## theaudiologist1 (Mar 12, 2021)

Hey guys. I have an R70x with 99dB/mW and the peak impedance at 900Ohms at the sub-bass. My amp can output 28mW at 300Ohms, so I guess 14mW at 600Ohms and 10.5mW at 900Ohms I think. My AMP does have gain options though, so the amp specs could just be at normal gain. Using a headphone calculator, I'm only 2mW away from the 12.6mW required for 110dB. Is that too low? Is it important for an amp to reach 115 and 120dB SPL or is 110dB the loudest most dynamic recordings get? Keep in mind my amp drives my heapdhones pretty loud and the bass sounds good too. Only classical recordings don't get loud and I think that's how they're designed to sound like. Also, my amp has an output impedance of 2.2 (4.4 in balance).


----------



## VNandor

theaudiologist1 said:


> I'm only 2mW away from the 12.6mW required for 110dB. Is that too low? Is it important for an amp to reach 115 and 120dB SPL or is 110dB the loudest most dynamic recordings get?


While your numbers are right, this isn't really how it works. *YOU *get to decide how loud you want your music to be in the first place. If you decide to listen quietly, then you don't even need your headphones to reach 110dB SPL. If you want to listen loudly you may need an amp that can push your headphones to 110dB SPL or even more. This is especially true if the kind of music you listen to is very dynamic. Listening this loud is also a really good way to damage your hearing in the long run.

There are two types of SPL (sound pressure level) to consider: the average SPL and the peak SPL. The sense of "loudness" mostly comes from the average SPL and not from the peak SPL. So if you play back music at an average of 80dB SPL it doesn't matter if it peaks at 110dB SPL, it's going to sound quieter than some other music that you play back at 90dB SPL average but with a peak level of 100dB SPL.

So the way to check if your amp could get your headphones to the loudness you want (besides just listening to it of course) is picking some average SPL you want to listen to and then checking how dynamic the music you listen to is. For example I listen to music at 70-80dB SPL most of the time and the music I listen to has an RMS ("average") level of -6 ~ -20dB so I have to add 6~20dB headroom to reproduce the peaks in my music. So even if I want to listen loudly to my most dynamic music, I will still most likely never push my headphones over 100dB peak SPL. After that all I have to check is the specs of my headphones and do some calculations the way you did to check what kind of amp I need for my listening habits.



theaudiologist1 said:


> My amp can output 28mW at 300Ohms, so I guess 14mW at 600Ohms and 10.5mW at 900Ohms I think.


You got that mostly right if you don't want to consider the output impedance of your amp (which you don't have to because it's really low compared to the impedance of your headphones), except I think you would get ~9,3mW at 900Ohms if you calculated it with 28/3.


----------



## 71 dB (Mar 13, 2021)

theaudiologist1 said:


> Hey guys. I have an R70x with 99dB/mW and the peak impedance at 900Ohms at the sub-bass. My amp can output 28mW at 300Ohms, so I guess 14mW at 600Ohms and 10.5mW at 900Ohms I think. My AMP does have gain options though, so the amp specs could just be at normal gain. Using a headphone calculator, I'm only 2mW away from the 12.6mW required for 110dB. Is that too low? Is it important for an amp to reach 115 and 120dB SPL or is 110dB the loudest most dynamic recordings get? Keep in mind my amp drives my heapdhones pretty loud and the bass sounds good too. Only classical recordings don't get loud and I think that's how they're designed to sound like. Also, my amp has an output impedance of 2.2 (4.4 in balance).



10.6 mW gives only 0.75 dB less sound than 12.6 mW. That's pretty irrelevant. Half the power, lose just 3 dB. At impedance peaks (resonance of driver) the headphone is more sensitive so it doesn't make sense to do calculations how much amp can deliver to that impedance. Do calculations for 1 kHz for example. Frequency response tells how that applies elsewhere.

Reaching those high dB values is only important if you want to listen to levels dangerous to your hearing. If the music is very dynamic (i.e. mostly quieter and more safe to ears), only the peaks here and there will hit the power limit causing distortion. Recordings get as loud as is your volume setting. 110 dB is just a _typical value_ given for the loudest parts of orchestral music, but if you go to a baroque music concert the peaks are far from that.

Your amp output impedance 2.2 Ω is so low compared to your cans that it is practically a short circuit. So no need to worry about it.


----------



## theaudiologist1 (Mar 13, 2021)

71 dB said:


> At impedance peaks (resonance of driver) the headphone is more sensitive so it doesn't make sense to do calculations how much amp can deliver to that impedance. Do calculations for 1 kHz for example. Frequency response tells how that applies elsewhere.
> 
> Reaching those high dB values is only important if you want to listen to levels dangerous to your hearing. If the music is very dynamic (i.e. mostly quieter and more safe to ears), only the peaks here and there will hit the power limit causing distortion. Recordings get as loud as is your volume setting. 110 dB is just a _typical value_ given for the loudest parts of orchestral music, but if you go to a baroque music concert the peaks are far from that.


so even the sensitivity i svaried at different frequencies? Oh I thought only impedance varied. But what is the loudest loudest peak that you can hear for a RECORDING (since even orchestral recordings get compressed a bit)? Are there recordings that hit 115dB max volume?

Also, are symphonies the most dynamic music out there?


VNandor said:


> While your numbers are right, this isn't really how it works. *YOU *get to decide how loud you want your music to be in the first place. If you decide to listen quietly, then you don't even need your headphones to reach 110dB SPL. If you want to listen loudly you may need an amp that can push your headphones to 110dB SPL or even more. This is especially true if the kind of music you listen to is very dynamic. Listening this loud is also a really good way to damage your hearing in the long run.
> 
> There are two types of SPL (sound pressure level) to consider: the average SPL and the peak SPL. The sense of "loudness" mostly comes from the average SPL and not from the peak SPL. So if you play back music at an average of 80dB SPL it doesn't matter if it peaks at 110dB SPL, it's going to sound quieter than some other music that you play back at 90dB SPL average but with a peak level of 100dB SPL.
> 
> So the way to check if your amp could get your headphones to the loudness you want (besides just listening to it of course) is picking some average SPL you want to listen to and then checking how dynamic the music you listen to is. For example I listen to music at 70-80dB SPL most of the time and the music I listen to has an RMS ("average") level of -6 ~ -20dB so I have to add 6~20dB headroom to reproduce the peaks in my music. So even if I want to listen loudly to my most dynamic music, I will still most likely never push my headphones over 100dB peak SPL. After that all I have to check is the specs of my headphones and do some calculations the way you did to check what kind of amp I need for my listening habits.


But isn't it true that you need to have a certain volume to hear all instruments, since some of the quieter instruments are only heard on higher volumes. At what average dB do you hear all instruments where the music is clear enough?

Also, what does "phase" mean that I saw in the impedance graphs?


----------



## 71 dB

theaudiologist1 said:


> 1) so even the sensitivity is varied at different frequencies? Oh I thought only impedance varied. But what is the loudest loudest peak that you can hear for a RECORDING (since even orchestral recordings get compressed a bit)? Are there recordings that hit 115dB max volume?
> 
> 2) Also, are symphonies the most dynamic music out there?
> 
> ...


1) Yes, that's one reason why the frequency response isn't dead flat. Recordings don't have any sound pressure level, only dynamic range. The recording doesn't know how loud the sound should be. Of course you can listen to at a volume level which makes the loudest parts hit 115 dB (if your gear has enough "juice" and your ears can take it), but you can also listen to the same recording 35 dB quieter meaning the loudest parts hit "only" 80 dB. When the recording was made, the sound pressure level varied in the hall. Near the orchestra mayby 108 dB. In the back row maybe 97 dB and so on... asking for correct dB level is like asking the correct picture size of movies. There isn't one. Picture can be small or big. Sound can be quiet or loud. It's up to what you prefer.

2) This is a complex question. Recordings of orchestral music tend to be dynamic, because usually the sound isn't compressed like it is with pop music for example. No loudness war. In practice the dynamic range is limited by background noise so a classical music concert isn't perhaps any more "dynamic" than a rock concert, or at least the difference isn't huge. Too much dynamic range can be annoying just as too little. 

3) Yes, because of equal loudness curves. At around 80-90 dB these curves start to be quite "straight".

4) It is the angular difference of voltage and current. Current can change "with" voltage (phase = 0), or it can change before or after if the system isn't purely resistive.


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## bigshot (Mar 14, 2021)

71 dB said:


> Reaching those high dB values is only important if you want to listen to levels dangerous to your hearing. If the music is very dynamic (i.e. mostly quieter and more safe to ears), only the peaks here and there will hit the power limit causing distortion. Recordings get as loud as is your volume setting. 110 dB is just a _typical value_ given for the loudest parts of orchestral music, but if you go to a baroque music concert the peaks are far from that



I used a SPL meter to measure the level of my speaker system at the loudest volume I was comfortable listening at. It was a little over 80dB. You might get a bit higher with headphones, (i know people who have unwittingly damaged their hearing because they didn't realize how much volume they were pumping into their ears.) but I doubt it would get over 85-90dB.

The peak level they quote for orchestral music is based on a listening position in the middle of the band a few feet from the brass section. From a normal listening distance the distance makes the peak drop down to the same peak I found in my speaker system, or a bit lower. 110dB is right at the point where you incur hearing damage. No one listens to music that loud. Commercially recorded music doesn't really have a dynamic range above 55dB. Your ears have a dynamic range of about 45dB at a time. They can adjust to more than that, but it takes time. A classical recording with peaks and valleys broader than 50dB is going to be very difficult to listen to. You'll be reaching to adjust the volume all the time.

I don't see any reason to worry about volumes above 90dB. Remember, the dB scale is (logarithmic), so 100 to 110 is a bigger jump than 50 to 60.

Another factor to consider is Fletcher Munson. At lower volumes your ears don't have a flat response. That's why amps have that loudness button to correct for it.


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## theaudiologist1

71 dB said:


> 1) Yes, that's one reason why the frequency response isn't dead flat. Recordings don't have any sound pressure level, only dynamic range. The recording doesn't know how loud the sound should be. Of course you can listen to at a volume level which makes the loudest parts hit 115 dB (if your gear has enough "juice" and your ears can take it), but you can also listen to the same recording 35 dB quieter meaning the loudest parts hit "only" 80 dB. When the recording was made, the sound pressure level varied in the hall. Near the orchestra mayby 108 dB. In the back row maybe 97 dB and so on... asking for correct dB level is like asking the correct picture size of movies. There isn't one. Picture can be small or big. Sound can be quiet or loud. It's up to what you prefer.
> 
> 2) This is a complex question. Recordings of orchestral music tend to be dynamic, because usually the sound isn't compressed like it is with pop music for example. No loudness war. In practice the dynamic range is limited by background noise so a classical music concert isn't perhaps any more "dynamic" than a rock concert, or at least the difference isn't huge. Too much dynamic range can be annoying just as too little.
> 
> ...



So at 90dB (which means at 110dB-115dB peaks) I can hear all the instruments? 90dB is already too loud for average SPL? Idk my levels but I'm guessing I listen at 85-90dB which means my peak SPLs will be 110dB-ish max.

Also, people here told me (or shilled me) that even though I can hear the song loud, because of the higher impedance of the sub-bass and my amp bring a bit weak there, my amp doesn't drive my headphones to their "full potential" whatever that means. Could that be true?


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## bigshot

There are a great deal of people who say things without knowing that of which they speak!


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## SoundAndMotion

bigshot said:


> There are a great deal of people who say things without knowing that of which they speak!


Case in point.


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## 71 dB

bigshot said:


> I used a SPL meter to measure the level of my speaker system at the loudest volume I was comfortable listening at. It was a little over 80dB. You might get a bit higher with headphones, (i know people who have unwittingly damaged their hearing because they didn't realize how much volume they were pumping into their ears.) but I doubt it would get over 85-90dB.
> 
> The peak level they quote for orchestral music is based on a listening position in the middle of the band a few feet from the brass section. From a normal listening distance the distance makes the peak drop down to the same peak I found in my speaker system, or a bit lower. 110dB is right at the point where you incur hearing damage. No one listens to music that loud. Commercially recorded music doesn't really have a dynamic range above 55dB. Your ears have a dynamic range of about 45dB at a time. They can adjust to more than that, but it takes time. A classical recording with peaks and valleys broader than 50dB is going to be very difficult to listen to. You'll be reaching to adjust the volume all the time.
> 
> ...


Yes, people worry about this too much. I also listen to music at levels of maybe 70-80 dB. I know the decibel scale well because I am an acoustic engineer (I't actually logarithmic).


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## 71 dB (Mar 14, 2021)

theaudiologist1 said:


> So at 90dB (which means at 110dB-115dB peaks) I can hear all the instruments? 90dB is already too loud for average SPL? Idk my levels but I'm guessing I listen at 85-90dB which means my peak SPLs will be 110dB-ish max.
> 
> Also, people here told me (or shilled me) that even though I can hear the song loud, because of the higher impedance of the sub-bass and my amp bring a bit weak there, my amp doesn't drive my headphones to their "full potential" whatever that means. Could that be true?


At those levels you danger/damage your hearing. You should hear "everything" at much lower level. Yes, 90 dB for average SPL is very loud. I measured loudspeakers for hifi-magazines. One watt of pink noise to 8 Ω = 2.83 Vrms. Typical loudspeakers give 80-90 dB at one meter at that power level. Sure, those speakers were inside a reverberation chamber, but the noise level was pretty loud. 

Amps may have difficulties with signal peaks, but it is another story how those short peaks translate into loudness levels for our ears. SPL meters use time weighting (fast, slow or impulse) so that very short peaks are averaged out. So, we can worry about if amps can produce enough power at peaks to keep the signal clean, but that's pretty much it.

The claim that your amp doesn't drive your headphones  to their "full potential" sounds bs to me.


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## VNandor (Mar 14, 2021)

71 dB said:


> The claim that your amp doesn't drive your headphones to their "full potential" sounds bs to me.


People seem to struggle with understanding how the amp interacts with the impedance curve of headphones. I had someone saying the amplifier is more likely to clip the signal around the frequencies where the impedance is higher than around the lower impedances. I couldn't convince him that higher impedance translates into less power drawn for headphone amplifiers. People see a big number for impedance and due to the big number, they automatically assume that it must be harder to drive than low impedance headphones.


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## theaudiologist1

VNandor said:


> People seem to struggle with understanding how the amp interacts with the impedance curve of headphones. I had someone saying the amplifier is more likely to clip the signal around the frequencies where the impedance is higher than around the lower impedances. I couldn't convince him that higher impedance translates into less power drawn for headphone amplifiers. People see a big number for impedance and due to the big number, they automatically assume that it must be harder to drive than low impedance headphones.



If the different parts of the spectrum have different impedances and sensitivities, doesn't that mean that they have different volumes?


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## VNandor

theaudiologist1 said:


> If the different parts of the spectrum have different impedances and sensitivities, doesn't that mean that they have different volumes?


You are right, it means exactly that. The so called frequency response is what tells you how the volume differs at the different frequencies. There are plenty of people who measure and publish their own  frequency response measurements, one of the most famous one is from Tyll at innerfidelity. Although he is retired, his measurements can still be found here.


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## theaudiologist1 (Mar 14, 2021)

VNandor said:


> You are right, it means exactly that. The so called frequency response is what tells you how the volume differs at the different frequencies. There are plenty of people who measure and publish their own  frequency response measurements, one of the most famous one is from Tyll at innerfidelity. Although he is retired, his measurements can still be found here.



So if the median volume is 85dB at the midrange, the sub-bass will have a lower dB? So you can't hear the bass as well? You have to increase the volume a lot to hear it? For example if you have a dynamic range of 20 it means 75dB on the loudest and 95dB at the quietest if the medium id 85dB right?


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## sander99

theaudiologist1 said:


> So if the median volume is 85dB at the midrange, the sub-bass will have a lower dB?


No, I think you are misinterpreting what @VNandor said as if the impedance curve is the only thing that influences the frequency curve. There is more going on, like:


71 dB said:


> At impedance peaks (resonance of driver) the headphone is more sensitive


So at a frequency where the impedance is higher you could still have the same, or even a higher level.


----------



## CADCAM

Can someone tell me the output voltage of your standard laptop headphone out? Also if you are feeding your external DAC from a laptops USB vs the output from a CD players digital output what effect can this have on volume? My NAD and Oppo disc players are 2V & 2.3V output respectively and the volume on my amp never goes beyond 9 or 10 o"clock but another member who has the same amp and headphones as me indicated his volume gets to 2 to 3 o'clock!!!
He feeds his DAC from a laptop where as I feed my DAC from the digital output of my disc players. So we both have the same OTL tube amp and 600ohm headphones but his volume is set much higher than mine.


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## castleofargh

CADCAM said:


> Can someone tell me the output voltage of your standard laptop headphone out? Also if you are feeding your external DAC from a laptops USB vs the output from a CD players digital output what effect can this have on volume? My NAD and Oppo disc players are 2V & 2.3V output respectively and the volume on my amp never goes beyond 9 or 10 o"clock but another member who has the same amp and headphones as me indicated his volume gets to 2 to 3 o'clock!!!
> He feeds his DAC from a laptop where as I feed my DAC from the digital output of my disc players. So we both have the same OTL tube amp and 600ohm headphones but his volume is set much higher than mine.


Do you also have the DAC in common?


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## CADCAM

castleofargh said:


> Do you also have the DAC in common?


No, same amp LD MKIII and same hp's Beyer 600ohm but his source is a laptop, mine is the cd player. 
I am using an external DAC and I believe he is using one as well. Also he has his amps gain set to high and mine is not, the LD has 4 gain setting 10-5-4-3 and I believe I am set at 5 for medium impedance hp's. So I would assume I'd be the one with higher volume settings being on the lower gain with 600ohm hp's.
Just wondering why the big discrepancy in volume settings.


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## sander99

CADCAM said:


> Just wondering why the big discrepancy in volume settings.


Likely in order of decreasing significance:
-Maybe the other guy is (knowingly or unknowingly) attenuating the signal in the pc (one of several volume controls).
-Maybe the other guy listens to higher SPLs
-Maybe his DAC or analog pc output produces a lower (maximum) signal level


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## castleofargh

Yup, that. 
To keep on with the list:
Some EQ, replaygain, soundcard DSP also leading to a lowered digital gain at the output. 
A mistake or a customer's request leading to different gain values for the same apparent gain setting.


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## bigshot

I just got a thing called Sound Booster for my work iMac. YouTube videos are all over the map when it comes to volume. Couldn't get some loud enough to listen to.


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## Tacman45

proton007 said:


> Hi all,
> 
> A lot of people ask this question in the other sections, so I thought this can be the thread to discuss it and hopefully it can act as a reference.
> 
> ...





proton007 said:


> Hi all,
> 
> A lot of people ask this question in the other sections, so I thought this can be the thread to discuss it and hopefully it can act as a reference.
> 
> ...


That was some phenomenal information, thank you.  Without trying to decipher all the math, I have a question.  My Topping DX7 Pro DAC/Amp on order has an output of 9.4 ohms on the XLR4 headphone out.  My Focal Clear MGs have a 55 ohm impedance.  I can connect them using the 4.7 ohm output on the 6.35mm jack but would prefer to use the XLR out if I can.  Could I damage my Mgs if I use the XLR and even if it would not do you think the impedance difference is enough to negatively affect their performance?  Thank you.


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## theaudiologist1 (Sep 1, 2021)

If my DAC/AMP can drive a pair of headphones that are 89dB/mW at 150Ohms to very loud levels (reviews said so), can it drive my headphones that are 99dB/mW at 470Ohms? My DAC/AMP outputs 28mW at 300Ohms.

Also on my 32Ohm headphones I was able to hear quieter noises I couldn't on my 470Ohms headphones. Is it because the 470Ohm headphone isn't loud enough to hear them?


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## castleofargh

theaudiologist1 said:


> If my DAC/AMP can drive a pair of headphones that are 89dB/mW at 150Ohms to very loud levels (reviews said so), can it drive my headphones that are 99dB/mW at 470Ohms? My DAC/AMP outputs 28mW at 300Ohms.
> 
> Also on my 32Ohm headphones I was able to hear quieter noises I couldn't on my 470Ohms headphones. Is it because the 470Ohm headphone isn't loud enough to hear them?


If you could get 28mW into 470ohm, the headphone would reach about 113dB with full scale signal. But how much power is that amp really delivering into 470ohm? I have no idea. 


About the second question, it can be the difference in FR between headphones, or the output level(or both). Or if the noises are generated by the amp, then it could be a matter of the amp not being a big fan of a low impedance loads.


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## VNandor

If the amp can deliver 28mW into 300 ohms it means that the amp can reach at least ~2.9V into 300ohm. If anything, the voltage slightly goes up as the load's impedance increases so I would assume the amp would deliver around ~18mW into 470ohms which is enough for 111~112dB SPL if the efficiency is 99dB/mW.


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## theaudiologist1

VNandor said:


> If the amp can deliver 28mW into 300 ohms it means that the amp can reach at least ~2.9V into 300ohm. If anything, the voltage slightly goes up as the load's impedance increases so I would assume the amp would deliver around ~18mW into 470ohms which is enough for 111~112dB SPL if the efficiency is 99dB/mW.


Despite that my very dynamic classical music (specially the DSD ones which for some reason are quiter than the PCM ones) is quiet on my 470Ohm headphones, and can't pickup some of the quieter sounds that my 35Ohm headphone does. If it could reach 111dB SPL I don't know what the problem is. The max impedance my heapdhone has is around 900Ohm in the lowerend.


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## VNandor (Sep 2, 2021)

theaudiologist1 said:


> Despite that my very dynamic classical music (specially the DSD ones which for some reason are quiter than the PCM ones) is quiet on my 470Ohm headphones, and can't pickup some of the quieter sounds that my 35Ohm headphone does. If it could reach 111dB SPL I don't know what the problem is. The max impedance my heapdhone has is around 900Ohm in the lowerend.


I didn't mention that it would reach these levels only at the moments when the music you are listening to is peaking at 0dBFS. Classical music typically have huge differences between the average and the peak levels. 25dB is fairly typical in my experience, some can even go as far as -30dB below the peak. So in these cases, you would listen at an average of maybe 81-86dB SPL and only the loudest parts would get to 111dB SPL. I'm guessing the loud parts of classical music is still loud enough, right?

The impedance swing at the low end shouldn't be a problem but the explanation might be a bit counter intuitive. A bigger impedance always draws less current for a given voltage. This could also mean that the headphone could be quieter around the impedance peak since less power is drawn, however I would expect the efficiency to also peak there which would mean that the headphone does require less power anyways to reach the same SPL. If you had a frequency response graph as well as an impedance graph of the headphone, the power drawn for a constant SPL over the frequencies could be calculated but it's kind of pointless, at least it would show that the headphone most likely doesn't need more power where the impedance peaks.


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## theaudiologist1

VNandor said:


> I didn't mention that it would reach these levels only at the moments when the music you are listening to is peaking at 0dBFS. Classical music typically have huge differences between the average and the peak levels. 25dB is fairly typical in my experience, some can even go as far as -30dB below the peak. So in these cases, you would listen at an average of maybe 81-86dB SPL and only the loudest parts would get to 111dB SPL. I'm guessing the loud parts of classical music is still loud enough, right?


Yes the loud parts are indeed very loud. I'm worried more about the quiet parts. I'm sure I listen to music at around 80dB average since 90dB would hurtmy ears. But assuming the peaks were 110dB and the dynamic range is 40dB (high even for classical) that means that the quietest parts of the music is at 70dB correct?



VNandor said:


> The impedance swing at the low end shouldn't be a problem but the explanation might be a bit counter intuitive. A bigger impedance always draws less current for a given voltage. This could also mean that the headphone could be quieter around the impedance peak since less power is drawn, however I would expect the efficiency to also peak there which would mean that the headphone does require less power anyways to reach the same SPL. If you had a frequency response graph as well as an impedance graph of the headphone, the power drawn for a constant SPL over the frequencies could be calculated but it's kind of pointless, at least it would show that the headphone most likely doesn't need more power where the impedance peaks.


I could not find a sensitivity graph for the R70x (my 470 Ohm headphones).


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## bigshot (Sep 2, 2021)

I don’t believe many commercial recordings have +30dB spikes above the normal peak level. I’ve found a couple like that. They were unlistenable. The normal volume was too low to listen to without turning the volume WAY up, and I spent the entire time turning the volume up and down so I could hear the quiet parts and avoid ripping the roof off the house. More is not better.

This sounds to me like an extrapolation of the common “fact” that orchestral peak levels reach 110dB. And yes they do if you stand directly in front of the brass section in a live performance. But no one listens to orchestral music like that. The front row might be 50 feet or more back from that. Volume level ten yards away isn’t the same as volume level an inch from your ear. Recordings are mixed to give a natural perspective from a theoretical best seat in the house. It isn’t mixed to sound like you’re sitting in the musician’s lap.

The most dynamic commercial recordings have a dynamic range of about 55dB. That reflects how it sounds in a concert hall. In fact, that is probably more dynamic than most concert halls. 110dB is past the flinch point and pushing the threshold of pain. When was the last time you attended a classical concert or listened to a symphony CD and experienced discomfort from volume spikes? That just doesn’t happen.

The peaks for very loud music are between 80 and 85 dB, not anywhere near 110.


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## theaudiologist1 (Sep 2, 2021)

bigshot said:


> I don’t believe many commercial recordings have +30dB spikes above the normal peak level. I’ve found a couple like that. They were unlistenable. The normal volume was too low to listen to without turning the volume WAY up, and I spent the entire time turning the volume up and down so I could hear the quiet parts and avoid ripping the roof off the house. More is not better.
> 
> This sounds to me like an extrapolation of the common “fact” that orchestral peak levels reach 110dB. And yes they do if you stand directly in front of the brass section in a live performance. But no one listens to orchestral music like that. The front row might be 50 feet or more back from that. Volume level ten yards away isn’t the same as volume level an inch from your ear. Recordings are mixed to give a natural perspective from a theoretical best seat in the house. It isn’t mixed to sound like you’re sitting in the musician’s lap.
> 
> ...


That's the problem: when listening to classical, in order to hear the quiet parts I have to put my amp on hi gain, max volume to hear them, and then the loud parts hurts my ears and I have to turn down the volume. Don't know how many dB the peaks are.

In one of the reviews for my DAC/AMP it said it can drive the 89dB/mW 150Ohm headphone on low gain at half volume and it gets loud. I put it on high gain max volume and it's still quiet (only with classical though).

 Another thing: my 32Ohm headphones are closed while my 470Ohm headphones are open. Maybe that's why it picks up the quieter sounds less?


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## bigshot (Sep 3, 2021)

Your headphones and amp are probably fine. The problem is bad engineering. More dynamics isn't automatically better. Too much dynamics is actually worse than too little. I find that BIS is the label that is the biggest offender at that.

Human hearing can only hear a dynamic range of about 40dB at a time. If there are immediate contrasts in volume that go beyond that, it either is irritatingly loud or you try to strain to hear it because it is too quiet to hear. It takes ears a minute or two to adjust to a lower or louder volume level. That's why the dynamics in commercially recorded music don't generally go much further than that.


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## 71 dB

bigshot said:


> This sounds to me like an extrapolation of the common “fact” that orchestral peak levels reach 110dB. And yes they do if you stand directly in front of the brass section in a live performance. But no one listens to orchestral music like that. The front row might be 50 feet or more back from that. Volume level ten yards away isn’t the same as volume level an inch from your ear. Recordings are mixed to give a natural perspective from a theoretical best seat in the house. It isn’t mixed to sound like you’re sitting in the musician’s lap.


An orchestra is not a small point source. When you stand "directly in front of the brass section", you might be 5 feet from the closest brass player, but some other brass players are much further away from you. You can't be 5 feet away from all players of the orchestra at the same time. That's why when you integrate the acoustical power at your ears, it gets "only" to 110 dB SPL. When you walk away to the "best seat in the house", your distance to those players who where originally furthest away from you increases much less relatively (relative distance matter in distance attenuation calculations). Your distance to the closest player perhaps 10-folds ( -20 dB), but your distance to the furthers players maybe only doubles ( -6 dB) or even less. That's why the integrated acoustical power at your ears doesn't drop 20 dB. Also, the hall has reverberation. It is far from a free-field situtation. The reverberation (without early reflections and direct sound) is the same level everywhere in the hall and increases the overall sound pressure level significantly. 

Reverberation radius rH is the distance where the sound energy densities of the direct sound and the reverberation are equal. It can be calculated using the formula

rH = SQRT ( Q * R / 𝜋 ) / 4,

where SQRT is simply square root, Q is directivity index of the sound source and R is room constant related to total absortion area A:

R = A / (1 - ā),

where ā is the average absorption coefficient.

Let's assume a concert hall of the size 40 m x 30 m x 15 m (133' x 100' x 50' for Americans). Desirable value for reverberation RT for an orchestral music hall of this size is about 1.8 seconds. Reverberation time can be calculated using the simple formula (there are better formulas, but this will do for this example):

RT = 0,161 * V / A,

where V is the volume of the hall. So, from this formula we get that total arborption are A = 0,161 * 40 * 30 * 15 / 1.8 = 1610 m². Now we can calculate the needed average absorption coefficient ā for the hall: ā = A / S = 1610 / (2 * 40 * 30 + 2 * 30 * 15 + 2 * 30 * 15) = 1610 / 4500 = 0.36. Now we can calculate the room constant : R = 4500 / (1 - 0.36) = 7031 and finally the reverberation radius assuming Q = 1.5 (almost omnidirectional sound source): rH = SQRT ( 1.5 * 7031 / 3.14) / 4 = 14.5 meters (almost 50 feet). 

This means that 50 feet away from the orchestra we are in the border of near field and free field. I'd say the peaks for the listeners are 90 - 95 dB.



bigshot said:


> The most dynamic commercial recordings have a dynamic range of about 55dB. That reflects how it sounds in a concert hall. In fact, that is probably more dynamic than most concert halls. 110dB is past the flinch point and pushing the threshold of pain. When was the last time you attended a classical concert or listened to a symphony CD and experienced discomfort from volume spikes? That just doesn’t happen.
> 
> The peaks for very loud music are between 80 and 85 dB, not anywhere near 110.


I wouldn't call music with peaks of 80 dB "very loud". Loud maybe. Peaks of 85 dB is perhaps "very loud", but yes, 110 dB is "damage your hearing in minutes" loud.


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## 71 dB

theaudiologist1 said:


> That's the problem: when listening to classical, in order to hear the quiet parts I have to put my amp on hi gain, max volume to hear them, and then the loud parts hurts my ears and I have to turn down the volume.


There is of course less dynamic types of classical music compared to romantic era and newer orchestral music.


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## theaudiologist1

71 dB said:


> There is of course less dynamic types of classical music compared to romantic era and newer orchestral music.


If you're talking about periods, then I hardly listen to classical. I listen to Baroque and Romantic. I don't know any clssical composers outside the big 3 (Mozart,Beethoven,Haydn) besides J.C. Bach. And I did notice Romanic was a lot more dynamic than Baroque.


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## 71 dB (Sep 3, 2021)

theaudiologist1 said:


> If you're talking about periods, then I hardly listen to classical. I listen to Baroque and Romantic. I don't know any clssical composers outside the big 3 (Mozart,Beethoven,Haydn) besides J.C. Bach. And I did notice Romanic was a lot more dynamic than Baroque.


1400 - 1600 Renaissance
1600 - 1750 Baroque
1750 - 1820 Classical
1820 - 1914 Romantic

Romantic era definitely is more dynamic. Hector Berlioz "invented" orchestration. Orchestras became bigger. The music became more turbulent and emotional.

However, I was talking about types of music: Instrumental / chamber / orchestra. If romantic era orchestral music is too dynamic, chamber music can be a nice option.


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## theaudiologist1

71 dB said:


> 1400 - 1600 Renaissance
> 1600 - 1750 Baroque
> 1750 - 1820 Classical
> 1820 - 1914 Romantic
> ...


That's something I noticed too, all the concertos and symphonies tend to be the most dynamic and hard to drive. I myself like all the types of Baroque/Romantic, as long as they have no vocals (I HATE vocals), but my favorites are always the concertos and symphonies.


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## gregorio

71 dB said:


> [1] This means that 50 feet away from the orchestra we are in the border of near field and free field. I'd say the peaks for the listeners are 90 - 95 dB.
> [2] I wouldn't call music with peaks of 80 dB "very loud". Loud maybe. Peaks of 85 dB is perhaps "very loud", but yes, 110 dB is "damage your hearing in minutes" loud.


1. You haven't accounted for absorption from the musicians, other audience members and carpets and chairs. Probably your figure isn't far wrong though, maybe a few dB less in most cases.

2. We have to be careful here, it's not a fixed point, even for the same individual! There's a perceptual effect at work here that many don't consider. I don't believe it's fully understood yet (although there are various theories/suggestions of course) but for some reason our perception of loudness changes with room size and distance to the sound source. Cinemas are calibrated to 85dB at a listening position in about the middle of the cinema, 85dB in a cinema is loud but not very loud. However, 85dB at the listening position in a sitting room or an good sized sound editing room sounds significantly louder. Perceptually, the difference in loudness of 85dB at the listening position in a very large room (cinema or concert hall) and an average sitting room/editing room is typically about 6-7dB. EG. 78dB in your sitting room sounds roughly the same loudness as 85dB in a cinema/concert hall. This is very rough though, the difference can be as little as about 3dB and in the case of a smaller room and sitting just a couple of meters from the speakers, as much as about 11dB. Clearly then, to some people, 80dB in their home listening environment could indeed be perceived as "very loud", especially if they're are older.


71 dB said:


> Romantic era definitely is more dynamic. Hector Berlioz "invented" orchestration. Orchestras became bigger.


Berlioz didn't invent orchestration. Orchestration had been around for centuries before Berlioz was even born, however he did write the definitive book on the subject (including it's prior history), it became required reading for composer students and was therefore very influential. I agree though that orchestras gradually became bigger and more dynamic. In Mozart's day an orchestra was around 40 musicians, Bach's typically around 20 - 30 and by the early part of the C20th, it became it's current standard full symphony orchestra size of around 90. That's in addition to the more sudden/dramatic changes in dynamics often employed by the Romantic era and later composers and the fact that most modern orchestral instruments are significantly louder than their Baroque and even Romantic era ancestors.  


theaudiologist1 said:


> That's something I noticed too, all the concertos and symphonies tend to be the most dynamic and hard to drive. I myself like all the types of Baroque/Romantic, as long as they have no vocals (I HATE vocals), but my favorites are always the concertos and symphonies.


Generally, symphony recordings have the largest dynamic ranges of all music genres, particularly the later romantic period symphonic composers such as Mahler, the post romantics such as R. Strauss and some of the impressionists and later composers, such as Ravel and Stravinsky.

G


----------



## 71 dB

gregorio said:


> 1. You haven't accounted for absorption from the musicians, other audience members and carpets and chairs. Probably your figure isn't far wrong though, maybe a few dB less in most cases.


Yes, I didn't do that, because I just wanted to make a simplified calculation that is definitely a little bit off, but gives us the ballpark.



gregorio said:


> 2. We have to be careful here, it's not a fixed point, even for the same individual! There's a perceptual effect at work here that many don't consider. I don't believe it's fully understood yet (although there are various theories/suggestions of course) but for some reason our perception of loudness changes with room size and distance to the sound source. Cinemas are calibrated to 85dB at a listening position in about the middle of the cinema, 85dB in a cinema is loud but not very loud. However, 85dB at the listening position in a sitting room or an good sized sound editing room sounds significantly louder. Perceptually, the difference in loudness of 85dB at the listening position in a very large room (cinema or concert hall) and an average sitting room/editing room is typically about 6-7dB. EG. 78dB in your sitting room sounds roughly the same loudness as 85dB in a cinema/concert hall. This is very rough though, the difference can be as little as about 3dB and in the case of a smaller room and sitting just a couple of meters from the speakers, as much as about 11dB. Clearly then, to some people, 80dB in their home listening environment could indeed be perceived as "very loud", especially if they're are older.


Music I hate at 85 dB is torturously loud to me while music I love at 85 dB is probably awesome level. Yeah, how loud something is to someone somewhere is subjective. Here we were talking about loudness in _concert hall_. When I did the mixing course last year, the teacher instructed to use 80-85 dB levels while mixing. Anyway, this discussion wasn't about how loud people find the sound. It was about how many decibels there is. For example cinemas are calibrated to 85 dB _regardless_ of what an older person thinks about it. It is considered generally loud but not very loud = good level.



gregorio said:


> Berlioz didn't invent orchestration. Orchestration had been around for centuries before Berlioz was even born, however he did write the definitive book on the subject (including it's prior history), it became required reading for composer students and was therefore very influential. I agree though that orchestras gradually became bigger and more dynamic. In Mozart's day an orchestra was around 40 musicians, Bach's typically around 20 - 30 and by the early part of the C20th, it became it's current standard full symphony orchestra size of around 90. That's in addition to the more sudden/dramatic changes in dynamics often employed by the Romantic era and later composers and the fact that most modern orchestral instruments are significantly louder than their Baroque and even Romantic era ancestors.


That's why I wrote "invented". 



gregorio said:


> Generally, symphony recordings have the largest dynamic ranges of all music genres, particularly the later romantic period symphonic composers such as Mahler, the post romantics such as R. Strauss and some of the impressionists and later composers, such as Ravel and Stravinsky.
> 
> G


I have a boxset of Ravel's orchestral works on Brilliant Classics (Eliahu Inbal) and the combination of how it has been recorded and Ravel's music makes it too dynamic to enjoy. That's the worst case of "too much dynamic variation" in my classical music collection. Other recordings of "very dynamic music" just work better.


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## gregorio (Sep 4, 2021)

71 dB said:


> [1] Here we were talking about loudness in _concert hall_. When I did the mixing course last year, the teacher instructed to use 80-85 dB levels while mixing. Anyway, this discussion wasn't about how loud people find the sound. It was about how many decibels there is. For example cinemas are calibrated to 85 dB _regardless_ of what an older person thinks about it. It is considered generally loud but not very loud = good level.
> 
> [2] That's why I wrote "invented".


1. Firstly, you seem to have missed my point: In addition to the subjective opinion that everyone has about what is loud, there's also a perceptual difference regarding decibels in significantly larger rooms and I specifically mentioned it because obviously there's a very significant difference between the size of a concert hall and the size of a consumer's listening environment. Using the cinema analogy again, 85dB in a cinema is considered "loud but not very loud", while exactly the same 85dB in a home listening environment is significantly louder, EG. Very loud, and that's for the same person with the same subjective opinion on what is loud! Secondly, as a calibrated level, 80-85dB is too high a level for mixing, unless it's film mixing in a full sized dubbing theater. Even film mixing in a sitting room sized environment should be done at a lower level than that, and films are mixed much quieter than music! As a peak (rather than a calibrated) level, 80-85dB for music mixing is probably about right, depending on the music.

2. And that why I corrected you, because he didn't "invented" orchestration, he just wrote a book about it's prior history and current (at the time) usage!

G


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## 71 dB

gregorio said:


> 1. Firstly, you seem to have missed my point: In addition to the subjective opinion that everyone has about what is loud, there's also a perceptual difference regarding decibels in significantly larger rooms and I specifically mentioned it because obviously there's a very significant difference between the size of a concert hall and the size of a consumer's listening environment. Using the cinema analogy again, 85dB in a cinema is considered "loud but not very loud", while exactly the same 85dB in a home listening environment is significantly louder, EG. Very loud, and that's for the same person with the same subjective opinion on what is loud! Secondly, as a calibrated level, 80-85dB is too high a level for mixing, unless it's film mixing in a full sized dubbing theater. Even film mixing in a sitting room sized environment should be done at a lower level than that, and films are mixed much quieter than music! As a peak (rather than a calibrated) level, 80-85dB for music mixing is probably about right, depending on the music.


I admit I missed your point of comparing concert halls and smaller rooms. In a concert the audience can't tell the orchestra to play quieter (only the conductor can do that) so the audience is at the mercy of what is happening or walk out. At home I can turn the volume down if the music is too loud for me. Or up if it is not loud enough. I kind of agree with you about the mixing levels. I felt that the overall volume levels used in the course were about 5 dB too high, but that's my opinion. Not only that, but I instantly noticed that the stereo image is way off to the left and mentioned about it to the teacher. The Genelec 8331A speakers they had should give very sharp and accurate soundstage in a studio room with proper acoustics, but that wasn't the case at all. Turned out the DAC had a glitch that made the right channel no less than 8 dB quieter! After fixing the issue the soundstage was as precise as expected. 



gregorio said:


> 2. And that why I corrected you, because he didn't "invented" orchestration, he just wrote a book about it's prior history and current (at the time) usage!
> 
> G


I am not a Berlioz expert, but I think his contributions were more than just writing a book. You do fine job at correcting people whenever needed, but there are situations where it becomes nitpicking.


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## theaudiologist1 (Sep 4, 2021)

So today I made my research on amp power and I want to know:

1) Is it true that if you use your amp at max volume at high gain, even if it drives the headphones loud, it will cause distortion, higher THD% and clipping since the amp is using its full power? It is said that a stronger amp outputting the same power to a headphone while not being at 100% is better than an amp using all its power? And how can I tell if it's distorting or clipping? I notice the lower end isn't as loud but I don't know it that's the amp or the recording.

2)This website:
https://nwavguy.blogspot.com/2011/09/more-power.html
claims 115dB peak SPL is preferred for dynamic recordings (which probably means classical).

*"The research indicates the average maximum level should be at least 85 dB, and with classical music, that puts the peak level up to 30 dB higher at a worst case 115 dB)."*

 How true is this and how much of a difference does it make? My amp drives my headphones to 108-112dB SPL peaks (maybe more on high gain).

3)Is it true that a weak amp will also skew the frequency curve of a headphone? Someone mentioned it in a thread.


----------



## theaudiologist1

gregorio said:


> Generally, symphony recordings have the largest dynamic ranges of all music genres, particularly the later romantic period symphonic composers such as Mahler, the post romantics such as R. Strauss and some of the impressionists and later composers, such as Ravel and Stravinsky.
> 
> G


Agreed. Mahler's music, specially his 8th, are some of the most dynamic recordings I ever heard.


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## 71 dB

theaudiologist1 said:


> So today I made my research on amp power and I want to know:
> 
> 1) Is it true that if you use your amp at max volume at high gain, even if it drives the headphones loud, it will cause distortion, higher THD% and clipping since the amp is using its full power? It is said that a stronger amp outputting the same power to a headphone while not being at 100% is better than an amp using all its power? And how can I tell if it's distorting or clipping? I notice the lower end isn't as loud but I don't know it that's the amp or the recording.
> 
> ...


1) Amps always generate some distortion, but at lower levels it is typically totally inaudible (unless we are talking about something like tube amps). When the power level approaches the maximum power level, distortion starts to rise rapidly. So, an amp may give 50 watts, but with large distortion (e.g. 2 % THD) and 40 watts at a low distortion rate such as 0.05 % TDH. As a rule to thumb 0.1 % THD or lower is safe/inaudible, but the audibility depends a lot on the frequency and distortion spectrum (odd/even harmonic etc.) If you can't tell if the amp is distorting or clipping you probably don't have a problem. What you _can hear_ is a problem. 

2) Peaks of 115 dB is very very loud (almost pain threshold!) and endangers hearing. Peaks of 100 dB allow very loud music listening experience. Dynamic music doesn't mean the peaks must make you deaf. It means the quiet parts are QUIET!

3) Too high output impedance together with uneven headphone impedance curve causes further curved frequency response, because the amp voltage is divided differently over the amp output impedance and headphone (+cable) impedance. Let's assume the output impedance of the amp is 33 Ω and the minimum and maximum impedances of the headphone are 25 Ω and 72 Ω. The level diffrence caused by the amp output impedance compared to a zero or very small output impedance is:

20 * Log10 ((72*(25+33)) / (25*(72+33))) = 4 dB.​
If the amp output impedance was just 1 Ω, we would have:

20 * Log10 ((72*(25+1)) / (25*(72+1))) = 0.2 dB.​
If the amp output impedance was just 33 Ω, but the headphone impedance was flatter (min 45 Ω, max 52 Ω), we'd have:

20 * Log10 ((52*(45+33)) / (45*(52+33))) = 0.5 dB.​


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## VNandor (Sep 5, 2021)

theaudiologist1 said:


> That's the problem: when listening to classical, in order to hear the quiet parts I have to put my amp on hi gain, max volume to hear them, and then the loud parts hurts my ears and I have to turn down the volume. Don't know how many dB the peaks are.


If the loud parts are already getting too loud and you have to adjust the volume during playback, that's not really the the amp's fault. Either you listen in a too noisy environment (even PC fans or HDDs can be too loud in this context) so you can't turn down the volume as much as you should without losing detail in the quiet parts, or if you listen in a quiet room but the music is still too dynamic, that's really just bad mastering.


theaudiologist1 said:


> Is it true that if you use your amp at max volume at high gain, even if it drives the headphones loud, it will cause distortion, higher THD% and clipping since the amp is using its full power? It is said that a stronger amp outputting the same power to a headphone while not being at 100% is better than an amp using all its power?


This isn't always true. For example a tube amp would most likely create more distortion at any volume level compared to an almost maxed out solid state amp even if the solid state amp's max output power is lower compared to the tube amp.


----------



## theaudiologist1

71 dB said:


> 1) Amps always generate some distortion, but at lower levels it is typically totally inaudible (unless we are talking about something like tube amps). When the power level approaches the maximum power level, distortion starts to rise rapidly. So, an amp may give 50 watts, but with large distortion (e.g. 2 % THD) and 40 watts at a low distortion rate such as 0.05 % TDH. As a rule to thumb 0.1 % THD or lower is safe/inaudible, but the audibility depends a lot on the frequency and distortion spectrum (odd/even harmonic etc.) If you can't tell if the amp is distorting or clipping you probably don't have a problem. What you _can hear_ is a problem.
> 
> 2) Peaks of 115 dB is very very loud (almost pain threshold!) and endangers hearing. Peaks of 100 dB allow very loud music listening experience. Dynamic music doesn't mean the peaks must make you deaf. It means the quiet parts are QUIET!
> 
> ...


2) so you're saying 100dB is enough for peaks? what about for a classical recording with a dynamic range of 40dB? Wouldn't that make the very quiet parts hard to hear at 60dB? What difference will a headroom of 110/115dB bring compared to a headroom of 100dB?

3) My DAC/AMP outputs 2.2Ohms in single-ended and 4.4Ohm in balanced mode and my two headphones have impedances of 470Ohm and 35Ohms. Will this problem affect my headphones?

Another thing: today I learned my DAC's max input is 1.5V (from source I guess), will this affect the amp output power?



VNandor said:


> If the loud parts are already getting too loud and you have to adjust the volume during playback, that's not really the the amp's fault. Either you listen in a too noisy environment (even PC fans or HDDs can be too loud in this context) so you can't turn down the volume as much as you should without losing detail in the quiet parts, or if you listen in a quiet room but the music is still too dynamic, that's really just bad mastering.


Sometimes I have the room window open, and my headphones are open headphones. Maybe that causes interference.


VNandor said:


> This isn't always true. For example a tube amp would most likely create more distortion at any volume level compared to an almost maxed out solid state amp even if the solid state amp's max output power is lower compared to the tube amp.


I see. So it all depends on the amp and solid state amps have a lower distortion than tube amps?


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## bigshot (Sep 5, 2021)

The average quiet living room has a noise floor of about 30dB. With a fairly dynamic track with a dynamic range of 40dB, That would allow you to boost the loudest peaks up to a comfortable level of 70dB and still hear the quietest parts just above 30dB. You'd have room to push it up to 80dB for a very loud listening level too.

40dB is a comfortable dynamic range for music. When you get into peak levels above that, you have to listen loud to hear everything. That's OK with Wagner, but maybe not so much for Haydn.


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## gregorio

theaudiologist1 said:


> 1) Is it true that if you use your amp at max volume at high gain, even if it drives the headphones loud, it will cause distortion, higher THD% and clipping since the amp is using its full power? It is said that a stronger amp outputting the same power to a headphone while not being at 100% is better than an amp using all its power? And how can I tell if it's distorting or clipping? I notice the lower end isn't as loud but I don't know it that's the amp or the recording.
> 2)This website:
> https://nwavguy.blogspot.com/2011/09/more-power.html
> claims 115dB peak SPL is preferred for dynamic recordings (which probably means classical).
> ...


1. Yes, driving an amp or headphone at max power will likely introduce audible distortion. As a decent rule of thumb, calculate what amp you need on the basis that you won't use it with a setting higher than about 75%. This will avoid the possibility of audible distortion from any half decent amp, although not necessarily from tube amps.

2. That's not true. The research indicates average max of 85dB for films in a cinema but when listening to audio in a home environment, the research indicates an average maximum level of 78dB, which is why 78dB is specified for calibrating TV loudness. Furthermore, these levels are referenced to -20dBFS, which means the maximum peak level in a cinema is 105dB (not 115dB) and in a consumer environment (TV) the max peak level would be 97dB. However, it might not be a bad ideal to aim for an amp that could output levels up to 115dB on the basis of the previous point, that you will always use it at settings lower than about 75% of that.

3. It can be true, @71 dB explained it.



theaudiologist1 said:


> Another thing: today I learned my DAC's max input is 1.5V (from source I guess), will this affect the amp output power?


No, what could affect your amp is the output (not the input) of your DAC, as obviously, the lower your DAC's output the more gain your amp will need to apply. This generally wouldn't be of any concern with a standalone DAC though.

G


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## 71 dB (Sep 6, 2021)

theaudiologist1 said:


> 2) so you're saying 100dB is enough for peaks? what about for a classical recording with a dynamic range of 40dB? Wouldn't that make the very quiet parts hard to hear at 60dB? What difference will a headroom of 110/115dB bring compared to a headroom of 100dB?


60 dB SPL isn't generally "hard to hear" in reasonable listening oonditions. Spoken communication happens typically at 60-70 dB and people can mostly understand each other. If the music has 40 dB of dynamic range, it means most of the music really is rather quiet. Otherwise the peaks get uncomfortable, even painfully loud. The difference is like similar to the difference of cars with stop speeds of 100 mph and 115 mph. You can go faster/louder, but should you? You may have a system that can give you 120 dB peaks, but when you listen to music you set the volume to comfortable levels and the peaks are maybe 100 dB.



theaudiologist1 said:


> 3) My DAC/AMP outputs 2.2Ohms in single-ended and 4.4Ohm in balanced mode and my two headphones have impedances of 470Ohm and 35Ohms. Will this problem affect my headphones?


The 470 Ω model should be fine, because the impedance is over 100 times bigger than the amp output impedance. The 35 Ω (earlier you said 32 Ω) was closed, right? Closed headphones tend to have very flat impedance curve meaning higher output impedance isn't an issue so you should be fine.



theaudiologist1 said:


> Another thing: today I learned my DAC's max input is 1.5V (from source I guess), will this affect the amp output power?


( brainfart pointed out by *gregorio* extracted with a brainfart extractor fan )

No.



theaudiologist1 said:


> Sometimes I have the room window open, and my headphones are open headphones. Maybe that causes interference.


Certainly! That would explain why 60 dB is hard to hear. You need much quieter listening conditions when listening to dynamic classical music! Listen to much less dynamic music when your window is open. Closed headphones can help too.



theaudiologist1 said:


> I see. So it all depends on the amp and solid state amps have a lower distortion than tube amps?


Yes. The distortions tube amps generate is the reason why people bother to use them anymore. Some people love the distortion because it makes the sound "warmer". On technical point of view solid state amps are far superior, but sometimes people don't want _technically_ correct answers.


----------



## bigshot

glad to see some answers being listened to


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## gregorio

71 dB said:


> 1.5 V sounds low, because line level signals are typically 2 V and can be even more than that.


Don't forget he's talking about a DAC, so the input signal is an eye pattern electrical signal, not a line level analogue signal. So in the case of say USB 2, the input signal would be about 400mV.

G


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## 71 dB

gregorio said:


> Don't forget he's talking about a DAC, so the input signal is an eye pattern electrical signal, not a line level analogue signal. So in the case of say USB 2, the input signal would be about 400mV.
> 
> G


Thanks for this correction, my bad! Some sort to brainfart. 
I totally forgot the DAC-part and only thought about an amp taking in analog line lever signal.


----------



## theaudiologist1

gregorio said:


> Don't forget he's talking about a DAC, so the input signal is an eye pattern electrical signal, not a line level analogue signal. So in the case of say USB 2, the input signal would be about 400mV.
> 
> G


Yes. My DAC/AMP has a microUSB which only has USB 2.0.


bigshot said:


> glad to see some answers being listened to


Glad to hear I'm not a burden at least



71 dB said:


> 60 dB SPL isn't generally "hard to hear" in reasonable listening oonditions. Spoken communication happens typically at 60-70 dB and people can mostly understand each other. If the music has 40 dB of dynamic range, it means most of the music really is rather quiet. Otherwise the peaks get uncomfortable, even painfully loud. The difference is like similar to the difference of cars with stop speeds of 100 mph and 115 mph. You can go faster/louder, but should you? You may have a system that can give you 120 dB peaks, but when you listen to music you set the volume to comfortable levels and the peaks are maybe 100 dB.
> 
> 
> The 470 Ω model should be fine, because the impedance is over 100 times bigger than the amp output impedance. The 35 Ω (earlier you said 32 Ω) was closed, right? Closed headphones tend to have very flat impedance curve meaning higher output impedance isn't an issue so you should be fine.


It's actually 35 Ohms. 32 Ohms was my guess before I checked the official specs (It's an ATH-MSR7). Using the 1:8 ratio on the 4.4 Ohm balanced out means the headphone needs to be 35.2 Ohms, almost exactly the same as my MSR7. Is that OK?


71 dB said:


> Certainly! That would explain why 60 dB is hard to hear. You need much quieter listening conditions when listening to dynamic classical music! Listen to much less dynamic music when your window is open. Closed headphones can help too.


Thanks. It's just that classical sounds way better with open headphones.


71 dB said:


> Yes. The distortions tube amps generate is the reason why people bother to use them anymore. Some people love the distortion because it makes the sound "warmer". On technical point of view solid state amps are far superior, but sometimes people don't want _technically_ correct answers.


One reason people like vinyls.


gregorio said:


> 1. Yes, driving an amp or headphone at max power will likely introduce audible distortion. As a decent rule of thumb, calculate what amp you need on the basis that you won't use it with a setting higher than about 75%. This will avoid the possibility of audible distortion from any half decent amp, although not necessarily from tube amps.


Thanks. I put my DAC/AMP on high gain max volume (only for dynamic classical) and the sound appears clean to me. I don't know how to detect distortion. There is some noise when I change the volume on my DAC but nothing noticable fromm the music.


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## 71 dB

theaudiologist1 said:


> 1. It's actually 35 Ohms. 32 Ohms was my guess before I checked the official specs (It's an ATH-MSR7). Using the 1:8 ratio on the 4.4 Ohm balanced out means the headphone needs to be 35.2 Ohms, almost exactly the same as my MSR7. Is that OK?
> 
> 2. Thanks. It's just that classical sounds way better with open headphones.
> 
> 3. One reason people like vinyls.


1. The 1:8 ratio is very general and outdated (headphones and amps driving them are different beasts than when that rule was created). To be on the safe side with _any_ headphone model out there one needs something like a 1:20 ratio rule, but much better is to know the impedance curve of the headphone and calculate how small output impedance is needed. In case of ATH-MSR7 (see the link below) the impedance is "ruler flat" meaning even output impedance of hundreds of ohms doesn't cause frequency response issues. So, 4.4 Ω is fine. So is 44 Ω or even 440 Ω! Flat impedance curve is one strength of closed headphones.

https://diyaudioheaven.wordpress.com/headphones/measurements/audio-technica/ath-msr7/

2. Perhaps true.

3. Yes, at least one of the reasons.


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## 71 dB

theaudiologist1 said:


> Glad to hear I'm not a burden at least


You are not a burden. People who reject information and insist on knowing better when they don't are a burden.


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## gregorio

theaudiologist1 said:


> Yes. My DAC/AMP has a microUSB which only has USB 2.0.


It's a bit weird they would give the spec of max input signal level. Input level is defined by the USB 2.0 specification, so either a USB 2.0 DAC can easily handle that spec or it won't work.

G


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## theaudiologist1 (Sep 7, 2021)

71 dB said:


> You are not a burden. People who reject information and insist on knowing better when they don't are a burden.


Thanks for the help, but at the end of the day I feel like my DAC/AMP sounds too quiet when listening to classical and the sound isn't "wide/full" outside the loudest moments. This is not the case with other genres. Is that my amp's problem?

Another thing: If I get balanced cables for my headphones, does the adapter also need to be balanced?


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## 71 dB

theaudiologist1 said:


> Thanks for the help, but at the end of the day I feel like my DAC/AMP sounds too quiet when listening to classical and the sound isn't "wide/full" outside the loudest moments. This is not the case with other genres. Is that my amp's problem?


No, it should not be your amp's problem. If it plays loud parts well, it should have even easier to play the quieter parts. You are just expecting less dynamic sound than classical music is.



theaudiologist1 said:


> Another thing: If I get balanced cables for my headphones, does the adapter also need to be balanced?


What adapter are you talking about? Didn't your amp have a balanced output (4.4 Ω?)


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## theaudiologist1 (Sep 7, 2021)

71 dB said:


> No, it should not be your amp's problem. If it plays loud parts well, it should have even easier to play the quieter parts. You are just expecting less dynamic sound than classical music is.


Thanks. I guess it is just my ears and me having a "grass is greener" thought that a more powerful amp will make my classical recordings sound more "full".


71 dB said:


> What adapter are you talking about? Didn't your amp have a balanced output (4.4 Ω?)


Yes it does. My amp has a weird 4 pin mini-XLR as balanced. So I have to get balanced cables for my headphones and also get a 3.5/2.5mm to 4-pin mini-XLR.
btw how do you input the Ohm symbol?


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## 71 dB

theaudiologist1 said:


> btw how do you input the Ohm symbol?


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## 71 dB

Someone with more knowledge about he balanced connection stuff could jump in, because I don't think I can say anything of value on that.


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## theaudiologist1 (Sep 7, 2021)

I noticed my DSD files (SACD rips) are quieter than my PCM files (CD Rips) (or maybe it's just the mastering)

Or, as you just said recently, it's just the way classical is.

I checked. It's pretty much just classical, more specifically Romantic that's quiet. Some of my non-Classical SACD's are still quieter than my PCM music, even the very dynamic PCM ones, but they're still less quiet than Romantic. Even Baroque and Classical were less quiet.


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## Sinistrail

At what point will the loss of volume/dynamic range/frequency response be apparent due to underpowering?
I was fancying this flat pair of headphones, but I'd end up connect it to something which is rated about 15 Ohms lower. That's a really negligible amount, right? Or is it not/it's too hard to measure with just this data?


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## 71 dB

Sinistrail said:


> At what point will the loss of volume/dynamic range/frequency response be apparent due to underpowering?
> I was fancying this flat pair of headphones, but I'd end up connect it to something which is rated about 15 Ohms lower. That's a really negligible amount, right? Or is it not/it's too hard to measure with just this data?


The _ratio_ of headphone and amp output impedances is more relevant than absolute values. Are you connecting 16 Ω cans to 1 Ω amp or 300 Ω cans to 285 Ω amp?


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## AxeMadman81

Hi Guys, I need Your Help
I've an ALL IN ONE Ampli+Dac by FX-AUDIO
The model is FX-AUDIO X6MKII
Taking a look at the specs I've found this:

No chance to find The Output impedence of The Amplifier,I've find This

*Output Power *940 mW @ 16 Ohms, 900 mW @ 32 Ohms, 700 mW @ 64 Ohms, 450 mW @ 120 Ohms, 200 mW @ 300 Ohms.

My question is: Is this Amplifier capable to drive HD600 safely? 

I'm using this calculator 

                                           Power Needed 

Safe               85  db           0.07 mW
Moderate      100 db          1.98 mW
Fairly Loud     110 db          20.01 mW
Very Loud      115  db         63.08 mW
Painful           120  db         199.69 mW

If I f I have correctly interpreted the numbers, to manage the Peak of Volume, I need 199.69 mw
My amp is able to manage 200mw at 300 ohm
Is it correct?

Thanks


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## Sinistrail

71 dB said:


> The _ratio_ of headphone and amp output impedances is more relevant than absolute values. Are you connecting 16 Ω cans to 1 Ω amp or 300 Ω cans to 285 Ω amp?


Eheh... I know I phrased it really badly. The headphones are 63 Ohms.


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## hamcha

I got a simple two for a not-so-smart noobie on old equipment and hopeful holiday addition.

Does an *old vintage receiver *(Kenwood KR-9400) have enough power to get the most out of the *Sennheiser HD 600* or *Hifiman Sundara*?
Does the *Little Dot 1+ *have enough power to get the most out of the *Sennheiser HD 600* or *Hifiman Sundara*?
Thank you!!!


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## harry501501 (Jun 26, 2022)

So a few non technical questions on DACs and amps.

1) I just bought the FIIO K5 Pro ESS and really enjoying it. It has three gains. When you go from one gain to the other, are you only adding power/volume?

E.g. I listen to my FIIO FD5 on LOW at 30%. I press to MEDIUM at same volume it's louder, at HIGH louder still. So is the increase in 'loudness' at 30% basically the whole point of a gain setting? OR is that added power to bring out the best in your headphone... E.g. tighter bass, more air, etc?

2) I read sometimes people saying a "good DAC should let you hear your gear and not the DAC", similar for headphone amps. I also read that different headphone AMPs should have no effect on your headphone gear, except for power. Which of these is more likely tho to have an impact on sound e.g. smoother, brighter, etc (dac or amp)? Or is it both equally? I do hear a difference between my SMSL DAC with AK4993 and FIIO with ESS for example. A lot of information and opinions seem very contradictory at times depending on the person. Very confusing.


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## castleofargh (Jun 26, 2022)

I see no indication of a change in impedance with a different gain setting, so most likely it just makes sound louder on the higher settings.
There can be different reasons to use gain settings, but often enough it’s to optimize things and make an amplifier easier to use with a wider range of headphones and perhaps IEM. It's nice to have gain settings but they don’t make your car go faster and won’t shoot lasers. It’s about voltage gain, which correlates with loudness(twice the voltage makes the music 6dB louder).
I don’t know that device, but there is a rule of thumb for gain that tends to apply to almost all amps sections:
Because higher gain almost always means higher noise, even though it’s rarely important and often inaudible, objectively speaking you should probably try to stick to the lowest gain value that manages to gives you enough loudness with a given transducer.
Also, depending on how the volume level is handled, it’s possible for the volume knob to show bigger channel imbalance near the lowest volume position. At a lower gain you have to turn the knob up and often avoid or reduce channel imbalance.


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## gregorio (Jun 27, 2022)

In addition to what castleofargh stated:


harry501501 said:


> I also read that different headphone AMPs should have no effect on your headphone gear, except for power.


This is correct. However, there are a few exceptions, tube amps will commonly add audible distortion and so can a solid state amp if it’s the wrong amp for your HPs, for example if it’s underpowered and you have to run it at or near max gain.


harry501501 said:


> Which of these is more likely tho to have an impact on sound e.g. smoother, brighter, etc (dac or amp)? Or is it both equally? I do hear a difference between my SMSL DAC with AK4993 and FIIO with ESS for example.


With the above exceptions for amps, plus a NOS DAC for DACs, no amp or DAC should have any “impact on sound”. Or more precisely, there is a minuscule impact on the sound but not enough to be audible.


harry501501 said:


> A lot of information and opinions seem very contradictory at times depending on the person. Very confusing.


That’s because psychoacoustics comes into play, the science of the perception of sound. For example, if we play music at a low level, it will obviously be quieter but it will also appear to change balance, it will seem to have less bass and treble, even though the balance hasn’t changed at all. This effect has been studied in detail for nearly a century and first published in the early 1930’s (Fletcher/Munson Equal Loudness Contours) and audiophiles can have many different ways of describing this perceived balance change: Richer, brighter, smoother, etc.

In addition there is a psychoacoustic effect which is closely related to the “placebo effect”; if we see or know a different piece of equipment is being used, our brain will often create a difference in our hearing perception to reflect this, even though there is no audible difference. If and what this (imagined/placebo) difference will be, varies from person to person, which is why there are different and often “very contradictory” perceptions and opinions. Unfortunately, audiophiles typically do not accept they, like all other humans, are subject to this “placebo effect” and therefore have to invent information to explain this audible difference in sound that doesn’t actually exist, which is why that information is often “very contradictory” and “confusing”.

G


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## bigshot

The biggest error I see audiophiles make is thinking that if they are aware of expectation bias, they can consciously suppress it by just listening more carefully. That belief shows a fundamental misunderstanding of the placebo effect. You can't eliminate human nature by force of will.


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## harry501501

Thanks for the feedback. I do try take the placebo effect into consideration. So when reviewers say "X amp is bassier or bass light... Y has a bigger than usual soundstage.... Etc"...  Is this nonsense?


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## castleofargh

harry501501 said:


> Thanks for the feedback. I do try take the placebo effect into consideration. So when reviewers say "X amp is bassier or bass light... Y has a bigger than usual soundstage.... Etc"...  Is this nonsense?


Who knows? A reviewer almost never bothers to use a setup with a switch to have near instantaneous comparison, and almost never does a proper volume matching before listening.
Of course actual blind tests to stop listening with their eyes is the ultimate rarity, so all in all, nobody knows for sure(certainly not the reviewer) if the impression is close enough to be considered right, or if it’s filled with made up stuff caused by a flawed test.
Sadly, reviewers and audiophiles tend to think all that is irrelevant to them, they ”know better”, they ”have experience”, as if knowing about biases magically made them go away. They’re so ignorant and/or so confident(usually goes hand in hand) that they really believe anything they feel to be objectively true about sound. It’s a level of delusion that always surprises me. Even more so when there is a constant reminder about objective and subjective stuff in audio forums. One would normally get a hint that maybe they’re not the same thing.

At some point it’s like basic psychology where someone tells you about a third person and you can see bits and pieces of the one talking to you based on what he/she has to say about that third person(you can find stuff about me right now  ). IMO it’s the same with reviewers. they end up talking about themselves and their biases/beliefs a lot more than they think. After a few reviews hopefully you can start to see how often the price changes their mind, how often they favor an amp just because it’s written ”balanced” or ”class A” on the box.


Of course some changes can happen and the final frequency response could be altered(it’s usually the amp + a given headphone’s impedance causing a certain amount of change instead of the amp itself always doing that alone). And soundstage... well, as I said recently somewhere, it’s used to describe anything and everything, and different people are still likely to create a more or less different interpretation of space anyway. Almost anything audible, visible, or from any other senses, has the potential to alter that interpretation.
So they could be correct about the description with that headphone only, or they could say ”soundstage this and that” because one amp has more distortions(tube amps usually do and it could reach audible levels), or again, simply because one is a little louder. That would be real sound difference. Or it could be any sort of bias altering their interpretation of what they think is sound. Could also be that they have a deal with a brand.
It’s the uncertainty that ruins everything. More controls over the variables is the only proper way to increase confidence.


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## gregorio (Jul 1, 2022)

harry501501 said:


> I do try take the placebo effect into consideration.


Which generally will have no effect whatsoever on whether you actually experience it or not in a given situation.  Unless of course one does more than just consider it and actually take steps to eliminate placebo, with a controlled test as castleofargh explained.

Placebo effect is a type of aural illusion, some illusions don’t work once you’re aware they’re just an illusion, others don’t work as well or change somewhat once you’re aware of them but in many cases, knowing about them and/or taking them into consideration makes absolutely no difference at all. The aforementioned Fletcher/Munson “curves” and balance appearing to change with volume is an example of the latter as is the stereo effect, and there are numerous others. Another example that surprises many people is the McGurk Effect, where our brain changes the word we think we’re hearing.


harry501501 said:


> So when reviewers say "X amp is bassier or bass light... Y has a bigger than usual soundstage.... Etc"... Is this nonsense?


Typically “yes”, it’s complete nonsense! There are various reasons why we might perceive say a “bassier” sound where in fact there’s no difference at all. For example:
1. Placebo effect due to some bias or combination of biases, expectation and confirmation bias being the most common but there are others.
2. The Fletcher/Munson “curves” if the volume is different.
3. How we are listening can obviously make a difference. If for example we listen to exactly the same track twice, without changing anything at all but during one of those playbacks we focus our concentration on the bass, then we’ll obviously perceive more bass/bass detail.
4. Reducing the amount of mids and/or treble can be perceived as the inverse, increasing the bass. This is virtually always the case if the volume is adjusted to compensate for a loss of treble.

However, there are various reasons why the bass might actually change when we change amps (or anything else) but which have nothing to do with that change. For example:
1. Typically when changing amps or another system component, we’ll have to remove our HPs/IEMs to do so. A slightly different position when we replace/reposition them, just a millimetre or two, can have a relatively very large effect on the amount of bass impacting our ear drum.
2. A similar situation can occur with speakers, a different seating or head position of just a couple of inches or so can make a significant difference to the amount of bass/treble entering our ears, due to the effects of room acoustics.
3. User error is also a possibility. For example, some EQ or other setting inadvertently engaged on one of the amps.
4. An impedance mismatch due to certain HPs/IEMs/speakers, as castleofargh mentioned.

And lastly, the amp may actually be “bassier”, for example some tube amps might add distortion in the bass/mid bass region.

ALL the above possibilities (in both categories) are far more probable than the last possibility (that the amp is actually “bassier”), unless you’re comparing certain tube amps of course. The problem, as castleofargh stated, is that audiophiles and audiophile reviewers typically just jump straight to this last possibility and will usually either just completely ignore the existence of all the other more probable causes of their “bassier” perception or, consider some (or very rarely all) of them but then fail to adequately eliminate them or just discount them regardless.

If we wish to be factually accurate or logical/“scientific”, then obviously we cannot just jump to the last possibility without eliminating the other possibilities, especially as those other possibilities are more probable. Therein lies the issue; despite implying and often asserting otherwise, many audiophiles’/reviewers’  ONLY concern is their perception and their (typically fallacious) assumption/belief of what’s causing it. Being factually accurate, logical, scientific or even rational about the causes of their perceptions are at best a distant 2nd place but more commonly, of no concern/interest whatsoever! This is due to either: Ignorance, incapable of critical thinking, marketing BS, being antisocial/a sociopath (simply not caring about misleading others and/or being disingenuous/a liar) or a combination of some or all of the above.

G


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## bigshot

The placebo effect is an subconscious bias. By definition, taking it into consideration won't make any difference. It's not a conscious decision.


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## redrol

Im personally tuning IEMs.  I take 3-4 weeks in general to hit the mark.  My own ears are not infallible and I do often run music too loud.  Time works it all out.  Fresh ears in the morning are my favorite.


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## ddlo (Jul 16, 2022)

bigshot said:


> The biggest error I see audiophiles make is thinking that if they are aware of expectation bias, they can consciously suppress it by just listening more carefully. That belief shows a fundamental misunderstanding of the placebo effect. You can't eliminate human nature by force of will.


very true! i myself couldn't identify between most decent dac/amp setups (much less cabling and other audio accessories like adaptors or mounts) in abx blind tests. however, as many knowledgeable headfiers here already mentioned, i often feel my cans/setup sounds different under different time/vol setting/wearing positions. while we hear differently and have different preferences on sound signature, it seems to me that the capability of most decent audio electronics have already exceeded the hearing capability of most listeners.

i can see the value of argument that personal enjoyment matters, no matter if there's actual/objective differences.  i enjoy beautiful packing or finely finished surfaces of my audio gear too (which has no impact in audio performance at all).  But it's quite wrong to spread the unfounded claims/myths clearly defying scientific evidences.  i often was puzzled why a headphone needs over 10W or even stereo amps to power when the least efficient of them, as far as i know, is still rated at 83dB/mW or why an exotic power cable matters when the miles of length before it is only perfectly adequate industrial grade (including aluminum ones!)

it's quite weird that so many in this hobby insist their bias is "true" in the face of so many obvious and subjective scientific evidence suggesting otherwise.  this sentiment seldom happens in other hobbies - i never saw mech watch lovers claimed the exemplary beautiful finishing or the double assembly process on ALS watches made any differences in terms of time keeping accuracy.  i also never heard anyone claiming titanium leica rangfinder special editions have any difference in image quality over the normal ones.  neither will shoe snobs claiming that bespoken JLL or saint crispin's is more comfortable than cheap nike sneakers. only audiophiles seem to insisting the minute details such as cable, materials of device enclosures, exotic mounts for electronic without moving parts, or even stickers could have profound impact to sound.

i myself see and value the effort and dedication putting into finely made products (even without any audible advantage) but it's misleading to claim audible improvement (in some cases) when there're clear scientific evidence against it (the claims that titanium/copper cases of DAP or hifi grade network switch or stickers that claim to bring "darker" background come to mind!). such obsession likely will cause more harm than good for this hobby.

just my 2cents


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## gregorio

Couldn’t agree more with practically everything you said, with the possible exception of this:


ddlo said:


> it's quite weird that so many in this hobby insist their bias is "true" in the face of so many obvious and subjective scientific evidence suggesting otherwise.


It’s not really so weird because the audiophile community is very closed. The vast majority of audiophiles are not “faced” with so much obvious scientific evidence. What they’re actually faced with is audiophile marketers, audiophile marketing and those who are reliant on it (such as reviewers and sites like this one), who do their best to make sure that audiophile consumers are not faced with the scientific evidence and who invent falsehoods to discredit the science if it is brought up.

G


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## BobG55

gregorio said:


> Couldn’t agree more with practically everything you said, with the possible exception of this:
> 
> It’s not really so weird because the audiophile community is very closed. The vast majority of audiophiles are not “faced” with so much obvious scientific evidence. What they’re actually faced with is audiophile marketers, audiophile marketing and those who are reliant on it (such as reviewers and sites like this one), who do their best to make sure that audiophile consumers are not faced with the scientific evidence and who invent falsehoods to discredit the science if it is brought up.
> 
> G


This Forum has saved me tons of money.


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