# Multiple balanced armature speaker systems with crossover networks



## Moz-Art

Hi,
  
 I'm starting this thread to share information about crossover networks for In Ear Monitors (IEM) with balanced armature speakers (BA). Please share your thoughts and experience.
  
 In this thread I will be talking about my experience while I do a trail and error process, making custom in ear monitors (CIEM) in a three way setup with a passive crossover. I'm ordering my stuff online from Mouser.com and I'm still looking for an analyzing tool like a 711 coupler to simulate the ear canal and test frequency respons from my setup cause I think that is a very important step in the trail and error stage. I will also share all the documentation on the products and processes that I use.
  
 What's the goal for me? Find the best speaker with the best frequency response for the chosen bandwidth or frequency and fitting crossover to create a reference speaker sound in a three way system.
  
  
 Resources:
  
 Speakers: Knowles speakers (www.knowles.com) or Sonion (http://www.sonion.com/) but you can't seem to buy these in small quantities
 Inductors : Still reading on best quality brands
 Capacitors: Still reading on best quality brands, these are the most expencive and difficult things of the crossover network.
 Resistors: Same as for the inductors, still looking and reading
  
 All of the above available at www.mouser.com
  
 Cables:
  
 You can a cable from Westone and make the female connector:
 http://www.westone.com/store/index.php/westone-music-products/accessories/epic-replacement-cables.html
  
 I prefer the Amphenol coaxial MMCX connector. You might know them from the Shure IEM. They are available at Mouser too.
  
 Equipment:
  
 You'll need a decent soldering station with tempature control. BA speakers are very sensitive for tempature and if it's a bit too hot, they brake.
  
 If you really wanna go the whole nine yards it would be best to have an artificial ear simulator.
 You can find one here http://www.bksv.com/Products/transducers/ear-simulators/ear-mouth-simulators/4157?tab=accessories
 There is a lot of software out there to use with this tool. I will post more about that later.
  
 You'll need to put all this in a shell but I don't want to focus on that as there are other threads that cover that. So please, let's talk about sound, speakers and crossovers.
  
 I have some documents I will share in my next post.
  
 Hope you join in and share.
  
  
 English is not my native language so forgive me for my errors.


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## Moz-Art

Some documents for reading time:
  
 https://dl.dropboxusercontent.com/u/85757794/CIEM/711%20receiver%20response%20and%20impedance%20rev%201.2.pdf
  
 https://dl.dropboxusercontent.com/u/85757794/CIEM/Earphone%20Design%20Guide.pdf
  
 https://dl.dropboxusercontent.com/u/85757794/CIEM/Knowles%20Earphone%20BA%202014%20ver%204.pdf
  
  
 https://dl.dropboxusercontent.com/u/85757794/CIEM/Crossover%20Networks.pdf


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## Moz-Art

Here you can find the Shure connector type in plastic shape
  
 http://effectaudio.com/product/shure-se535-connectors/
  
 They are expencive but sure look good!
  
 You can get cheaper ones at Mouser.


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## Moz-Art

In a normal situation where you would have three classic speakers, you would create a crossover network using capacitors, resistors and inductors. Sonion writes on its site that balanced armature speakers are highly inductive and using inductors as a low pass filter is not very effective. 

So the low pass filter should be created using a resistor and a capacitor in series.

I'm wondering if there are any problems using inductors at all in a crossover network for BA speakers.

A high pass filter can be bet made with a capacitor, also because capacitors are more predictable then inductors.

Better check out how to best make the band filter for the mid range without using inductors.

Anybody who knows more about the use of inductors with balanced armature speakers, let me know.


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## MuZo2

As far as I know 99% use RC crossover with acoustic filters  sometimes for low pass.


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## Moz-Art

I know. Most of the brands say they use a three way crossover network but most of the time it's only a high pass you'll find.

That is what I want to find out. Is it possible to use a real three way crossover network with balanced armature speakers inside the environment of a in ear monitor.


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## MuZo2

I dont think its possible.


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## Moz-Art

Would you like to go demper intro that?

Edit *Damn autocorrect. It should have been "Would you like to go deeper into that"*


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## MuZo2

Two way designs  use tweeter with cap. Woofer with resistor & acoustic damper.
 Three way would be additional mid driver with rc band pass.
 So there are no real speaker like passive crossovers.


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## Moz-Art

This is what Westone say on their website:
  
*Individually hand-crafted in Colorado Springs, Colorado, the UM Pro 30’s superior build quality and sound signature are unmatched. Tuned for performing artists, the three-way crossover is matched to individual low, mid and high frequency drivers to make your mix smooth and balanced across all frequencies.*
  
 Basically they are lying? Or is it possible?


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## MuZo2




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## Moz-Art

Thanks MuZo2.
  
 From what IEM is this picture?


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## MuZo2

moz-art said:


> From what IEM is this picture?


 

 W3


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## Moz-Art

I should have guest that.
  
 I've been talking to a CIEM designer this morning and it seems that a "way" system is a wide term in CIEM. It's mostly a combination of some capacitors to make a high or low pass filter and sending full range signals to speakers that have a specific and narrow frequency respons. Or they just send full range signals to every speaker and us acoustic filters to filter and damp out unwanted frequencies.
  
 Correct me if I'm wrong here.
  
 But it is possible to make a threeway crossover network using only resistors and capacitors. Apparantly you can use inductors too with BA speakers but they are less predictable and more expensive. So it's just a matter of testing the best combination speakers and see if they even need a filtered signal or can handle the full range signal.


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## Moz-Art

Not many people here that are trying this kind of stuff anymore.


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## SingaporeDriver

Hi there, have you come up with an ideal configuration of crossover(s) and drivers that you can recommend?


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## Xymordos

I always thought that using acoustic crossovers (such as length and size of tubing) is a better way for crossovers than components?


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## modulor

Thanks for starting this resource, Moz-Art!  I too am interested in learning more about BA applications and appropriate crossover networks so I've been reading about it a bit myself, but your links to Knowles documentation is definitely helpful.  I know Sonion has some documentation on their site about each unit as well, but they are much more difficult to acquire (I asked their customer support specifically about the AcuPass 1723 and there is a minimum of 1000 units per order) so I'll be sticking to Knowles units for now.  Another alternative to Mouser is Digikey, and the prices are pretty much identical so whichever gives you the better shipping price 
	

	
	
		
		

		
			




  
 Unfortunately, proper artificial ear measurement tools are extremely expensive, I recall Rin's write-up on the IEC 60318 stating that each unit was roughly $3k!  I suspect the other options like the GRAS RA0045 (or 43AG ear simulator) and B&K 4157 are similar...and after reading about what goes into them, rightfully so.  Now, I've definitely seen some DIY alternatives out there but it's hard to say just how accurate (rather, how much less accurate) they will be.  I guess one option would be to make friends with an audiologist or hearing-aid technician and see if they would be willing to measure your units - that could be a practical way to get accurate measurements without breaking the bank haha. I think at first I will go the route of attempting a fairly simple DIY measurement rig of some sort (still researching if it's worth the effort) using some software compensation and then subjective impressions from myself and others.  I'm interested to see your findings though!  I have come across some other potentially useful resources:
  
http://www.audiologyonline.com/articles
  
http://hearinghealthmatters.org/waynesworld/
  
http://www.aes.org/technical/documentDownloads.cfm?docID=177
  
http://www.comsol.com/model/download/154497/models.aco.generic_711_coupler.pdf
  
http://etd.dtu.dk/thesis/210600/MSc_thesis.pdf
  
I think for starters I am planning on trying a design using GQ-30783 (so just a two way crossover config at first) and then go from there, just due to availability and ease of use.  The GQ series seems to implement a similar design as Sonion's AcuPass but I'm not sure if they have a similar type of low-pass filter implemented in already.  I guess an alternative is to acquire a used TDK BA200 and cannibalize the drivers from there (I really love the BA200) but it's a shame nobody sells Sonion units in lower quantities.  I would say judging by the measurements they are fairly similar in topology though.  My other current IEM, the InEar SD-3, does utilizes the GQ-30783 in conjunction with an additional woofer (possibly a Sonion driver) but I believe it is still a two way crossover. I really like what these types of units mean for designers...primarily for simplicity in construction but also because it seems like a good base to start with if you're adding more in.  What do you think?​  
http://cymbacavum.com/2014/03/26/sonions-acupass-technology-making-things-easier-for-everyone/​  
http://www.sonion.com/Products/Transducers/Receivers/~/media/Files/Products/Application%20Notes/Transducers/AN_1723_AcuPAss_Rev001.ashx​  
 I've been sifting through some threads here on DIY CIEM, as piotrus-g and a few other well-known DIY'ers have posted some really useful information and this one has quite a bit:
  
http://www.head-fi.org/t/430688/home-made-iems
  
 I'll share any additional findings I come across


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## MuZo2

Where are you located, some Sonion distributors minimum order is 10pcs.


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## modulor

muzo2 said:


> Where are you located, some Sonion distributors minimum order is 10pcs.


 
 In the US - so far I've only contacted Sonion US but I know they have a few EU distributors...do you happen to know which might have low minimums?


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## zogster

Just came across this thread while looking into making my own custom IEMs.
  
 Great info Moz, thanks - did you write the Instructables piece also?
  
 Anyhooooo... if you're after Sonion drivers in small numbers, Colsan Microlectronics (http://www.colsanmicro.com/) in the UK will sell you as few as you like, though the per-unit price is significantly higher than buying 25+.


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## Moz-Art

Hey,
  
 It's been a while since my last post and this is mostly cause I've been very busy at work and because I spent a long time choosing the right speaker combination. I've ordered a rang of speakers and they arrived in the mail last week. Next week I start building my crossover network.
  
 To test the frequency respons of the setup, I've contacted a few university's and found one that had the ear simulator and was able to convince them to use it a couple of times. Because I don't assemble the in ears myself, I contacted a local lab specialised in hearing aids, they can recreate my setup over and over because they can test the frequency response in a special box (not ear simulator) to match my reference pair. They can also test that the left and right monitor has the same response.
  
 I'll try to post some pictures soon!
  
 M.


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## MuZo2

Cool , Good luck


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