how to hook up 2 subs

gmorris

Lets say I have 2 subs I want to hook up. How do I do this?

Here are some scenarios I've come up with & what I see wrong with them:

1. Using the speaker level inputs, connect the left speaker output on the amp to the left speaker input on the left sub, connect the left sp. out on sub to left satellite speaker. Do the same for the right channel. What I see wrong here is by only using one speaker level input at the sub, I may be "missing out" on some bass info. (is this true?) The satellite speaker should be fine. Advantage: normal amount of speaker cable required.

2. Connect both left & right speaker outs from the receiver to left sub, run speaker cable from sp. out of first sub to sp. in on second sub, then connect satellites to second sub speaker outs. Disadvantage: twice the speaker cable needed. Advantage: both subs get right & left signals, and sat. should be fine.

3. Using the line level inputs (RCA) on both subs (no LFE input on the sub) connected to the reciever. My question here is how to do this using the single RCA sub output from the amp. Can you connect the single RCA sub out to just one of the RCA sub inputs? Disadvantage: I'm pretty sure I'd be double crossover-ing the sub.

What is the best way to hook up two subs. My particular sub amps have speaker leve & RCA inputs. They do not have an LFE input. Also, I don' think you can turn off the sub amp crossover.

Thanks,
Greg

John K.

Greg, use connection 3. From the single sub out on the receiver run a shielded coaxial cable to one of the subs. There you plug the RCA connector on the cable from the receiver into a short "Y" connector(about $3 at RadioShack)and plug one end of the Y into a line level input on the sub. The other branch of the Y then connects to an extension sub cable(however long you need to reach the other sub)with a female connector to connect to the Y and the other end a regular RCA plug to fit a line level input on the second sub. An alternative arrangement, if more convenient, would be to have a Y connector for the receiver sub output and run separate coaxial cables all the way to each sub.

Since you say that you can't bypass the sub crossovers, you should turn them all the way up so as to get them as far away from interfering with the receiver crossover to the sub as possible. If you have a choice, the receiver crossover filter should be set at 80hz, unless your speakers have very little output that low.

gmorris

Thanks for your input John.

What do you think of my speaker level arrangements? I am an oldschool believer when it comes to connecting subs. I believe the best way to hook up a sub is with speaker level so you can use the crossover on the sub. I think it is easier to blend the sub with the mains. I just am not sure what the best way to this is with 2 subs. What do you think?

The more I think about it, scenario #1 seems like the better way, it is just as if each main speaker had its own sub.

John K.

Greg, my thoughts are that back when receivers didn't have subwoofer outputs and bass management(and stereo receivers which still don't)the speaker level connection was the only one possible and the sub had to have an adjustable internal crossover to try to get a "blend" with speakers having various bass capabilities. When a receiver has a sub out and bass management at a certain frequency or choice of frequencies the "blending" is automatically taken care of and we don't have to fool around trying to work with what is often an inaccurately calibrated sub crossover control.

So, let the receiver do the work in bass management that it's designed to do by using the line level sub output. If the sub has a switch or input to bypass its crossover it should be used. If not, it should be turned all the way up to get it out of the way of the crossover filter on the receiver.

gmorris

That makes sense. Very tough to argue with that.

So if I use a Y adapter to hook up both subs with the recievers sub output, will having only 1 RCA style connection going into the right or left RCA input on the sub work? I will check with the manufacturer to see just which input (R or L) should be used with the sub out.

Thanks for the ideas,
Greg

Dr. Spec

I prefer a decent quality Y adapter at the sub pre-out and 2 cables (one to each sub).

Daisy chaining subs can (not always) introduce some signal degradation and noise that would otherwise not be present.

Also, the sub filters do not always have the same filter rates as the AVRs. While the really top end AVRs have variable high and low pass filter rates, the industry standard is 12 dB/octave for the high pass filter and 24 dB/octave for the low pass filter. This is also (not surprisingly) the THX standard. Not all subs have a 12/24 high/low pass filter rate for the speaker level connection, and can actually sound different when compared to a low level connection.

In addition, the signal is filtered before the amp stage when using the BM circuit in the AVR. This significantly lightens the load on the AVR amps since they are relieved of the high current bass duties. Many report a more dynamic and powerful (and cooler running) amp stage after high passing all the speaks using the internal BM. A speaker level connection forces the amp stage to provide a full range, full power signal to the subwoofer filter circuit and you do not reap this important benefit.

I agree, 80 Hz is almost ideal for music and movies when using a 12/24 filter rate, and this is also the THX standard sub crossover frequency. Although some prefer lower for music, remember the 12 dB/octave high pass rate will allow the speakers to play pretty low before signing off completely. And for HT, if you high pass lower than 80 Hz, you will risk lopping off the top of the LFE channel unless your AVR has the specific capability of retaining a separate crossover frequency just for the LFE channel. Few AVRs have this ability, and the LFE channel is usually summed with the low passed bass from the surround channels.

So in summary - USE THE SUB PRE-OUT! It is much better than the sub filter for the many reasons stated above.

Doc

gmorris

Thanks Doc. Very thourough explanation. I will try using the sub out with the Y adapter.

John K.

Greg, you can use either the right or left line level input on the subs; they are combined inside the sub and it doesn't make any difference.

Doc, I agree with your comments. Note that the first arrangement I suggested wasn't daisy chaining, but merely putting the Y adaptor near the first sub with a short cable from the other branch of the Y to the second sub. This would be a bit more convenient if the two subs are close to each other(e.g. both in the same corner, as some suggest).

Dr. Spec

Originally posted by John K.
Note that the first arrangement I suggested wasn't daisy chaining, but merely putting the Y adaptor near the first sub with a short cable from the other branch of the Y to the second sub. This would be a bit more convenient if the two subs are close to each other(e.g. both in the same corner, as some suggest).

I misread that John, sorry. You are absolutely right, this is no different than Y splitting at the sub pre-out and might save some $$ with a shorter sub cable.

Regards,

Ed

athertonwj

Thanks for the excellent answer! Using the y-adaptor at the sub out on the receiver is what I believed to be the correct way to do this, however, I can never get anything out of my second sub (regardless of which sub is connected to which cable); I have swapped them, and only one will work at a time. I have a Cambridge Soundworks 10 sub (100 watts) and a polk (100 watt) sub connected via good quality rca sub cables to a quality y-adapter which goes to the sub out on my Denon 3806 receiver. Any ideas as to what I may be missing?

Thanks!

Bill

Knucklehead

Possibly a bad y-cable? I'll ask a dumb question here. Have you verified both subs work correctly alone? If so, kinda narrows it down to the Y-cable. I have my subs configured this way, no problems so far. I have a couple of y-cables laying aroud, I'll be happy to send you one no charge if you think it might help.

athertonwj

Hi there,

Yes, both subs work on their own, and I have actually run them each directly to the sub out and through one side or the other of the y-cable, independently, to the receiver, however, obviously, that doesn't completely rule out the bad y-cable. I have to believe, though, that if I'm able to get a signal through either side of the y-cable to either sub, the y-cable is good, unless there is a possibility that a y-cable can pass the signal through either side (basically as an extension) but not through both sides at once. Ideas? I wondered if there is a setting on bypass/filter on one or both subs that need to be setup.

Thanks,

Bill

apphd

When one sub will not work is it not turning "on" in the auto mode, or is it on but no sound? Maybe an issue with the sensitivity of the auto on circuit so it just isn't seeing enough signal to turn one of the subs on. Anyway if it works the way you have it now sit back and enjoy.

athertonwj

Nope, both subs are powered on, just no sound out of both at the same time.

Knucklehead

what kind (brand) of Y cable are you using? Also, what brand subs are you using?

athertonwj

It's a Monster Y and I have a Cambridge Soundworks 10 sub (100 watts) and a polk PSW 10 (100 watt) sub

TNRabbit

Many subs have an input and output RCA connection, so you can just "daisy-chain" them...

athertonwj

Yeah, I gigure that'll be the next thing if I can't eliminate the y cable as the issue. Thanks!

w_coyote

you could try adjusting your sub trim level in your avr to send a stronger signal to the subs. might be worth a shot. just a thought.

gtu2004

Knucklehead wrote: »

Possibly a bad y-cable? I'll ask a dumb question here. Have you verified both subs work correctly alone? If so, kinda narrows it down to the Y-cable. I have my subs configured this way, no problems so far. I have a couple of y-cables laying aroud, I'll be happy to send you one no charge if you think it might help.

can you give me a link to how a Y-cable for 2 subs looks like (maybe from monoprice)? I want to double the sub but am unsure how to do this.

Knucklehead

gtu2004 wrote: »

can you give me a link to how a Y-cable for 2 subs looks like (maybe from monoprice)? I want to double the sub but am unsure how to do this.

http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10218&cs_id=1021803&p_id=663&seq=1&format=2