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Hello everyone!

First off, thanks again to everyone for the replies to my first thread on hometheatershack. You guys rock!

Anyway, the other night, I was reading somewhere (cant remember where though, stupid beer) about a HT setup using 2 subs fed with a stereo signal and how this setup was somehow better than the classic mono setup. It just so happens, I have two 12" subs identical to the 15" sub I was planning to build my sonosub with and I got to wondering...

So, first question - is there any truth to what I was reading? Will sending stereo signals to a left and right sonosub sound better than a mono signal to a single sonosub? Now, I realize that obviously two subs will have more output than one, but will the stereo signal make it sound better in any way than a mono signal?

Second question - assuming the answer to the first question is yes, I'll need a stereo amp to power them, such as a behringer ep2500. How easy (or difficult) are pro-amps to hook up to a HT setup? Will I need any other equipment or can you just connect the amp to the receiver and the subs to the amp like you can with a dedicated subwoofer amp like the dayton amplifiers from PE? What do I do (if anything) about a low pass and a high pass subsonic crossover (or whatever it's called that filters out those nasty low low frequencies)? Don't forget that I'm a total HT newbie when it comes to pro amps!

Thanks again in advance for any help!
Jason

(my apologies if this thread is in the wrong section)
 

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Hello everyone!

First off, thanks again to everyone for the replies to my first thread on hometheatershack. You guys rock!
Hi Jason, and glad to hear you're having a good time!

So, first question - is there any truth to what I was reading? Will sending stereo signals to a left and right sonosub sound better than a mono signal to a single sonosub?
Well, Mike is right in his response to your post. The sub output is, by definition, a mono signal (that's the ".1" of the "5.1" or "7.1"). You could send L/R full range signals to the subs, and apply LPF somewhere (some subs have it built in, or you could do it with a BFD (BFD is the Behringer Feedback Destroyer, the primary weapon of choice here at the HTS for sub EQ) or other external crossover), or you could run dual mono subs.

Quality would just depend on the setup. For example, two bad subs wouldn't stack up agains one good sub. Two great subs might just give you more output. Some people believe that using two non-co-located subs causes more problems and that you should simply co-locate them to get the extra SPL benefit. Some people believe that using two non-co-located subs smoothes the frequency response. I used to use three subs (two each built in to my mains, and a stand alone sub in the corner), and I got good results. Nowadays, I'm using full-range mains (no built-in subs) in conjunction with a huge IB sub, with good results. Both were somewhat meticulously EQd with REW and a BFD. Anyway, the point is that there's no clear answer, and you'll have to listen, measure and test for yourself! I believe that either way, you will be able to get stunning results with a little work.

I'll need a stereo amp to power them, such as a behringer ep2500. How easy (or difficult) are pro-amps to hook up to a HT setup? Will I need any other equipment or can you just connect the amp to the receiver and the subs to the amp like you can with a dedicated subwoofer amp like the dayton amplifiers from PE?
To connect a "normal" RCA to the EP2500 isn't hard, but you'll need a connector that has RCA on one end and XLR on the other. If your preamp/receiver has balanced outputs, you can use that to feed the EP2500 directly. Or, if you are using a BFD to EQ your sub's output signal, you can go balanced from the BFD directly to the EP2500. In any case, it's not hard to do, and the part(s) you need can easily be found (probably around $10 at RS or PartsExpress/Monoprice).

What do I do (if anything) about a low pass and a high pass subsonic crossover (or whatever it's called that filters out those nasty low low frequencies)? Don't forget that I'm a total HT newbie when it comes to pro amps!
Well, your preamp/receiver will most likely do the crossovers for you. The (mono) sub signal at the sub output jack should already be crossed over at whatever frequency you specify. Even if you were using an off-the-shelf sub or sub amp that has a built-in crossover, you should disable that built-in crossover, and opt to use the one that's implemented in your preamp/receiver. Now, if you choose to implement stereo subs using full-range main L/R signals, then yes, you will have to apply a low pass filter yourself. I'm doing this myself using some of the filters available in the BFD, and it works just fine. Admittedly, this is a more complicated path, and if you decide to go that route, post up your questions, and I'm sure we can get you going. There are also a bunch of other active, external crossovers available from Behringer and others...

Hope that helps! Good luck!
 
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Hi stereo sub outputs seem to be very rare on av amps but the top and near top of the line Yamahas do have them and sometimes a mono as well.

The sub channel on Yamahas is derived from the front and rear mixed together, and the mono sub from all channels when listening to music and movies from the LFE channel as outlined in the Yamaha manuals.

The sound with true stereo subs is so much more rhythmical and rounded as appose to two mono LFE subs IMO as two monos can sound a little monotonous and boring after a while during A to B testing.

I have tried the front outputs of my Yamaha A1 set to large via a behringer Cx-3400 crossover and found the output near identical to the sub left and right outputs, so as explained in the last reply it would be fine to use the main stereo signal for the right channel and the left as normal from LFE channel, or both subs from the front outputs set to large or if the front outputs are in use maybe zone 2 output.

The crossover is very helpfull with added output for better control of the subs so maybe you could purchase a behringer cx-3400 or cx2310 as they are very cheap and great value for money, or a dcx 2496.
 

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Yes 2 subs works fine in stereo but you need a stereo crossover to drive them (I do not know any HT receiver or processos that can drive 2 stereo subs, some of them have 2 sub out, but this is the same signal on the 2 outputs).

In home theater the .1 channel is a LFE that is used for sub frequency AND for sub effects.

I think that Otto have a good setup : 2 stereo subs for music, plus 1 Cinema sub for movies on the LFE channel.

Actualy, I got 2 subs with each of my front speaker but the carry the same LFE signal (not stereo). For my room, it works, fine. But I want to add a stereo xover to check out how it sounds in real stereo.

JP
 

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In theory, bass frequencies produced by subwoofers is so low that you cannot 'localize' them. In other words if you were blindfolded in a room with a subwoofer and were told to point at where it was coming from you would not be able to. In this context there would be no advantage to having 2 subs but real world applications don't always work as theorized.

Also, having two subs in different locations means each sub will have a different response at the seating position so you may end up losing certain bass frequencies that are only occuring in the Left channel for instance simply because the 'left' sub is in a null at that spot. From experience, I've had my theater in rooms where the sub is behind the seating position and the bass still sounded like it was coming from the mains. Your mind takes it's bass 'cues' from the higher frequencies in the mains and thus ties the bass to that location. One example is at the end of Independence Day after the alien mothership has been destroyed. Debris enters from surround right and all of the bass travels with it even though it is coming from the subwoofer.

Hooking up a pro amp is as easy as any other. You will just need a cheap RCA to 1/4" adaptor.
 

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Stereo bass has been debated a few times over at some other forums in the past, with me being strongly in favor of using multiple subs wired for mono use so that you get the cleanest, most powerful presentation possible. Using two subs for just the right and left main signals and a third for just LFE will really limit the potential of your bass.
 
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