# How do subwoofers connect to an amp?



## alex98uk

I'm quite new to speakers and stuff (been into headphones more). However, I am looking into a new setup. I want a subwoofer as i'm into quite bassy music (electro/dub etc...). How do you wire a sub up to an amp? Do they have their own plug, does it wire to speakers etc...?
   
  I've been looking at amps, but I never know whether I can hook a sub up to them or what?


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## 3X0

Generally subwoofers have their own built-in amplifier, and hook up to a pre-amplified sub-out/LFE-out or pre-amplified RCA outputs via RCA cables. Some subwoofers also have speaker-level inputs that you connect to the speaker-level outputs of your amplifier via speaker wire, though the internal amplifier on the subwoofer is still doing the work. Few subs have speaker-level outputs that pass through the signal from the amplifier to speakers, but generally the speaker-level input-output transition negatively impacts the signal.
   
  Very few subwoofers are passive, in which case you will have to dedicate an amplifier to these units and wire it up via speaker cable. They end up being very expensive to get right, and generally don't perform any better than the best of active-powered subwoofers in the appropriate price range.


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## alex98uk

Quote: 





3x0 said:


> Generally subwoofers have their own built-in amplifier, and hook up to a pre-amplified sub-out/LFE-out or pre-amplified RCA outputs via RCA cables. Some subwoofers also have speaker-level inputs that you connect to the speaker-level outputs of your amplifier via speaker wire, though the internal amplifier on the subwoofer is still doing the work. Few subs have speaker-level outputs that pass through the signal from the amplifier to speakers, but generally the speaker-level input-output transition negatively impacts the signal.
> 
> Very few subwoofers are passive, in which case you will have to dedicate an amplifier to these units and wire it up via speaker cable. They end up being very expensive to get right, and generally don't perform any better than the best of active-powered subwoofers in the appropriate price range.


 
   
  Ah, thank you, this is what I was looking for. So, most subs just have red/white RCA cables and attach to a Line-Out plug, or is there a dedicated plug in which the sub has to be connected to? Do most amplifiers have a sub-out connector, or just the more expensive ones? I was looking at the Cambridge Audio 640A V2 (Can't afford the new ones!). So, from the picture below, the amp would connect to the "pre-out" RCA jacks?


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## 3X0

Quote: 





alex98uk said:


> Ah, thank you, this is what I was looking for. So, most subs just have red/white RCA cables and attach to a Line-Out plug, or is there a dedicated plug in which the sub has to be connected to? Do most amplifiers have a sub-out connector, or just the more expensive ones? I was looking at the Cambridge Audio 640A V2 (Can't afford the new ones!). So, from the picture below, the amp would connect to the "pre-out" RCA jacks?


 

 Yes, you would have to connect the pre-out RCA jacks to the line-in RCA jacks on the subwoofer via speaker cable. Lower-end subwoofers will have only a single RCA line-in/sub-in/LFE-in so you will only have to merge the outputs. Almost all subwoofers have just the inputs, so you'll have to buy the RCA cables for the hookup if they're not provided.
   
  Most 2-channel stereo amplifiers (music usage) have pre-amplified outputs only. Sub-outs and LFE-outs are used almost exclusively in AV receivers (home theater usage).


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## alex98uk

Quote: 





3x0 said:


> Yes, you would have to connect the pre-out RCA jacks to the line-in RCA jacks on the subwoofer via speaker cable. Lower-end subwoofers will have only a single RCA line-in/sub-in/LFE-in so you will only have to merge the outputs. Almost all subwoofers have just the inputs, so you'll have to buy the RCA cables for the hookup if they're not provided.
> 
> Most 2-channel stereo amplifiers (music usage) have pre-amplified outputs only. Sub-outs and LFE-outs are used almost exclusively in AV receivers (home theater usage).


 
   
  Cool, I think that just about answers everything! One more question, how would you merge two RCA cables from the Pre-Out jacks to a single plug for the Line-In on the subwoofer? Is there some sort of converter?
   
  What is the difference between LFE out, Sub Out and Pre-Out? Anything in particular?


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## chronomitch

Most subwoofers have RCA input jacks and speaker level inputs. Additionally, subwoofers may have a low-pass filter which filters out any high frequencies so that they the subwoofer doesn't try to play them. Depending on the subwoofer, this low-pass filter may be defeatable or may only work on the speaker level inputs. It just depends on the model, so read the subwoofer's manual.
   
  Amplifiers designed for home theater purposes (what you find at Best Buy) usually have a single RCA out jack labeled "LFE" (low frequency effect) or "SUB OUT." In this case, the amplifier either sends the LFE channel in a 5.1 mix (i.e. from Dolby Digital or DTS) directly to this jack or mixes in low frequencies from other channels and sends it to this jack. This LFE RCA jack should be connected to either the left or right RCA input jack on the subwoofer. It doesn't matter which one since they get mixed together by the subwoofer. Additionally, you should turn off the subwoofer's low-pass filter since the amplifier takes care of that job.
   
  Stereo amplifiers, on the other hand, usually do not have an output jack specifically for LFE signals because they do not mix low frequencies into a signal channel like a home theater amplifier does. In this case, you can either connect the pre-out RCA jacks (both left and right) to the subwoofers RCA input jacks (both left and right), or run another set of speaker wires for both the left and right channels from the amplifier's speaker outputs to the subwoofer's speaker inputs. In either case, you will want to enable the subwoofer's low-pass filter since you will be sending the full frequency spectrum to it.


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## alex98uk

Quote: 





chronomitch said:


> Most subwoofers have RCA input jacks and speaker level inputs. Additionally, subwoofers may have a low-pass filter which filters out any high frequencies so that they the subwoofer doesn't try to play them. Depending on the subwoofer, this low-pass filter may be defeatable or may only work on the speaker level inputs. It just depends on the model, so read the subwoofer's manual.
> 
> Amplifiers designed for home theater purposes (what you find at Best Buy) usually have a single RCA out jack labeled "LFE" (low frequency effect) or "SUB OUT." In this case, the amplifier either sends the LFE channel in a 5.1 mix (i.e. from Dolby Digital or DTS) directly to this jack or mixes in low frequencies from other channels and sends it to this jack. This LFE RCA jack should be connected to either the left or right RCA input jack on the subwoofer. It doesn't matter which one since they get mixed together by the subwoofer. Additionally, you should turn off the subwoofer's low-pass filter since the amplifier takes care of that job.
> 
> Stereo amplifiers, on the other hand, usually do not have an output jack specifically for LFE signals because they do not mix low frequencies into a signal channel like a home theater amplifier does. In this case, you can either connect the pre-out RCA jacks (both left and right) to the subwoofers RCA input jacks (both left and right), or run another set of speaker wires for both the left and right channels from the amplifier's speaker outputs to the subwoofer's speaker inputs. In either case, you will want to enable the subwoofer's low-pass filter since you will be sending the full frequency spectrum to it.


 

 Yeah, i'll be using a Stereo Amp, not a home receiver. So, if I buy a sub, I need to make sure it has "low pass filter". This I guess is just activated/deactivated via a switch on the back of the sub? I think I have my head around everything now!


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## chronomitch

Most decent subs have both a switch to turn the low-pass filter on and off and a dial to set the frequency cut-off point. Generally speaking, 80hz is a good cut-off point, but it all depends on your speakers and purpose of your setup. Also, you may not even want to turn the low-pass filter on. It just depends on your preference and speaker/amplifier setup. For example, I have a 2.1 setup with some small bookshelf speakers (B&W 686) and an HSU STF-2 subwoofer, and I find that it sounds better with the low-pass filter off because it allows the subwoofer to pick up and play the mid-bass better, a place where the speakers are a little weak.
   
  Just experiment and do whatever sounds best to you.
   
  Also, I'm not sure what brands you're looking at, but I'm a big fan of HSU subs. They are definitely not the best looking subs, but they give some of the best value (and sound) for the money, IMO.


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## alex98uk

Yea, 2.1 is what I want. It's kind of annoying, I was hoping there would be another line-out that I could use to pass onto my LD MKIII headphone amp. That way I could use the same source, DAC and just switch between headphones and speakers. But, if the subwoofer uses the pre-out, I guess I can't connect my headphone amp anywhere


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## chronomitch

In that case, why don't you connect the subwoofer using the Speaker B terminals? That would reserve the pre-out RCA jacks for your headphone amp.


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## alex98uk

Quote: 





chronomitch said:


> In that case, why don't you connect the subwoofer using the Speaker B terminals? That would reserve the pre-out RCA jacks for your headphone amp.


 

 You sir have good ideas! Is there any difference between using speaker B and Pre-Out jacks? I assume they both pass through the full spectrum? Just out of interest, is there any real advantage over bi-wiring speakers?
   
  Lastly, the pre-out will be an OK source for the Headphone Amp right and the Zero '09 an OK DAC (in terms of usability).


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## 3X0

Quote: 





alex98uk said:


> Yea, 2.1 is what I want.


 

 You will only get 2-channel audio proper. The .1 is specific to home theater usage and AVRs where the lower frequencies are mixed into the discrete LFE channel (the .1 in x.1 setups).
   
  You should be connecting the headphone amp to a fixed line-level output, not a pre-amplified output.


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## chronomitch

Actually, on second thought, you should probably connect your headphone amp to one of the "Rec Out" outputs on your integrated amplifier. The Rec Out is the same thing as a Tape Out, which is just a loop output from whatever is input (i.e. there is no volume control or amplification). This will prevent the source signal from being amplified twice (once in the integrated amplifier and once in the headphone amplifier). You can then use the Pre Outs for the subwoofer.
   
  *Edit*
  3X0 beat me to it.


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## alex98uk

OK, cheers guys. So to sum up:
   
  My headphone amp will go on the Rec Out
  Sub wired up to either speakers terminal B or pre-out (leaving space for another set of speakers if needs be).
  The sub should have "low pass filter" ability
   
  Excellent, well I think that has answered all my questions, now just to look for some nice speakers and a sub. Rep+ is just "thumbs up" on Head-Fi right?


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## Shogster

Sorry for bringing up the dead,but im in almost the same situation.I bought a Dali Sub E9F,and it has LFE and L/R Line Input.My M-Audio AV42 Speakers have also L/R Line Input.I have connected the speakers to my Fiio E10K with a 3.5mm to 3.5mm from the left speaker to the lineout of the Fiio.My question is do i need an amplifier or a reciever to hook the sub with the speakers and the Fiio?


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## voxie

Hi, are you thinking of a powered / active Subwoofer or a passive one? "passive need to be powered by an external amp, the same as traditional speakers. A powered Sub has its own internal amp that you connect to its own power source and line through to you receiver / amp.


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## Shogster

The Dali Sub is powered,also my speakers are powered.Im asking if i can connect the sub,the speakers and the Fiio amp/dac so i can use the system without a reciever?Is it possible,and if yes what cables will i need?A Y splitter maybe?Nor sure how all things connect thats all.Also,the Fiio has a coaxial out,if that helps out.
 If i connect the Fiio to the sub with a 3.5mm to 2rca cable into the Line input of the sub,how do i connect my speakers then?


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## al404

I'm bring this back up because I can't figure if I can connect a subwoofer to a my mini amp SMSL SA-36A

I read in the posto to use the Pre-Out jacks but I can't understand what is it
I have 2 RCA ( L/R ) to mini Amp IN and then output connectors to speakers


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## ProtegeManiac

al404 said:


> I'm bring this back up because I can't figure if I can connect a subwoofer to a my mini amp SMSL SA-36A
> 
> I read in the posto to use the Pre-Out jacks but I can't understand what is it
> I have 2 RCA ( L/R ) to mini Amp IN and then output connectors to speakers



That's because you can't do it that way since your amp doesn't have a sub output port - all it has is a line signal input and speaker outputs.










You need something that has something like this:

HT Receiver


 


Stereo Receiver


 


Car Audio Processor


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## al404

but the AMP of the original post doesn't seem to have it neither
it says to use the "Pre-Out jacks" but can't understand what it is, maybe a pre amp output?


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## ProtegeManiac

al404 said:


> but the *AMP of the original post* doesn't seem to have it neither



What amp on the original post?


 




al404 said:


> it says to use the "Pre-Out jacks" but can't understand what it is, maybe a pre amp output?



You mean this one? 


 


The difference between a "Subwoofer (Preamp) Output" and a "Pre(amp) Out(put)" is that the latter is fullrange stereo. 

In most HT receivers the subwoofer output may be labeled "LFE" for "Low Frequency Effects," aka the ".1" or ".2" when a receiver or system is described as a 5.1, 7.1, or 7.2 Dolby Atmos. It either runs what is specifically is in the LFE or ".1" channel of the surround sound program (ex a Blu Ray) but that has some kind of leeway so it can be cut at a higher or lower frequency depending on how much bass the mains can handle before they need help from the subwoofer (or however you want to shake the HT room). 

When playing regular stereo audio all of these just apply some kind of crossover or low pass filter to the 2.0 audio.

You can still use a fullrange preamp output that way but you have a few problems:
*
1. Your SMSL amp doesn't have that either, so it doesn't actually matter that that Cambridge amp has it or not, you still don't have it and therefore can't utilize what doesn't exist.
*
2. Depending on the implementation:
a. There might be a selector that selects only one of either speaker amp output or the preamp output, _not_ both simultaneously. If the amp is designed to run like that then you're basically choosing between all bass or no subwoofer.
b. In some amplifiers like the NAD 304, there is no internal wiring that connects its preamp circuit to the power amp circuit - it just has ports on the rear connected by a jumper. You can use an RCA Y-splitter from there and connect it to both the subwoofer and the amplifier circuit, or the subwoofer and a separate amplifier.
*
3. Your amp doesn't have that.

*
Your best bet if you're going to continue using that amp is if your subwoofer has High Level (ie amplified speaker signal) Input. Look at its plate amp - if you see terminals that look like speaker cable connectors, then run the cables from your SMSL amp into those terminals on the amp's High Level Input, and then run speaker cables from the subwoofer's high level/speaker output.


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## al404

ok, thanks


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