Why dual subwoofers ?

Just got a new processor ( EAD 8000 pro ) that has outputs for two ( stereo ? ) subwoofers. What advantage is there to going with two subs ? Does it really make a difference ?
Using two subwoofers is often the cheapest way to increase your bass output, clean up any bass distortion, and add to the overall impact.

More importantly, using two subwoofers can help eliminate a lot of the bass problems you have in a typical room without using equalization. It won't be as effective, but it's sure a good start.
You get better responce across the listening enviornment. so it is easier to position them.

Also, subs are supposed to be "Non directional" well, this aint always so, if you park one near each speaker stereo sounds a bit better.

plus at the office you can say "I got dual subwoofers" and sound cool.
It really cleaned up my bass. Now it's infinitely more accurate and, for whatever scientific principle, less boomy.
Mostly the above said is not really a good assesment of the Pro's and Con's.
Adding more subs(in this case two) can increase the obvious dyanmic range of a system, by adding more bass to the room potentially. At the very least, you can run two subs at less output than one single sub, for more dynamic potential and ease/effortlessness. That said, you can also run stereo bass(which I'm not sure your pre offers). This allows for each sub to only have to deal with Bass from the left or right channels, mixed with the LFE or .1 channel, rather than handling all the bass symultaneously.
Yes, you can smooth out potential bass mode problems by placing one sub so that it is placed to counteract bass peaks in a room, thus smoothing response overall, by not coupling well at certain frequencies, if the other sub is placed where it does excite certain frequencies. (i.e, one sub placed in a peak at say 40hz, and the other placed in the null at 40hz). When the two subs are balanced well, it evens out frequencies avaraged between the two better, rather if placed in different strategically calculated locations. Also, with STEREO BASS, you can get better potential bass separation, detail, and imaging, less distortion potentially, just like stereo woofers in a full range speaker...all to varying degrees depending on execusion, acoustics,effectiveness of set up, calibration, etc.
Basically, two subwoofers can offer a lot of advantages IF SET UP CORRECTLY! The problem here is that most would probably cause more damage than good from lack of knowledge of what they're doign if they don't implement things properly.
For instance, it's very easy to get phase cancelation from comb filtering. at certain frequencies(likely one or two different freq's), especially in "mono" dual sub configs. You can also put two subs in tandem "Peaks" at certain bass frequqencies, compounding bass modes. You can put subs at distances from each other and the wall boundaries that causes more bumps and valleys in the response as well, without getting into too many details there.(See "Haus effect/Shreoder effect", others)
Basically, I think people can't set up one sub well enough mostly, let alone two or more! But, in the right hands, dual or multiple subs can be very effective if done correctly. INfact you can do much better in the hands of a skilled person who's putting the system together. Two subs can help maximize out put, smooth response, increase range, separation, imaging, etc.
The key here is you gotta know what you're doing...otherwise, you're just adding more speakers without knowing what's happening
More is always better right?

It's either easier for placement because you have two subs to make up for any errors, or harder because you have twice the errors.

I really have not made up my mind on this one yet.....

"plus at the office you can say "I got dual subwoofers" and sound cool." YEP

Robedk, I belive that the dual subwoofer outputs on your
preamp have the same .1 signal. The second one is for use
on large rooms where one sub might not be enough. Another
reason is when one wants to use two small ones instead of one large one and blend the system with the room decor.

I use two subs on a 2 channel system, one gets the signal
from the left channel and the other from the right one.
The sound is awesome, they are big (Linn AV-5150) but the
sound (bass) did improved a lot. I started the system with one sub, didn't like it because I felt that the bass was coming from one side of the room. When I got the second one
the image came back. As stated by Themadmilkman,Slappy & Vvrinc the use of two subs will cancel some of the satnding waves and the bass will be cleaner. Hope this helps.
Well, I just ordered the second sub( another Velodyne HGS 15 ). BTW, the rest of the speakers are B&W Nautilus( 802's - mains / 803's- surrounds / HTM1 - center ). I'll let you know what I think once I get it in the system. Thanks for the feedback !
Actually, I have couple questions. Since my AVR does not have two outputs for two subs, is it true that I can use a Y connector for dual subs? If such is the case, does any A'gon member know if the sound is as comparable as the AVR w/ two outputs for 2 subs? If we I want to go w/ 2 subs, should I get a new AVR w/ two outputs for dual subs, or should I save the money by purchasing a Y connector. I have the Yamaha RX-V1400, which has the microphone for automatic room calibration, and the AVR is used as a pre/pro. The amp is a 5-channel Marantz w/ 150wpc. HT setup is 5.1. AR speakers, Phantom 8.3 (X4) for main and surround speakers, and Phantom 252C (X1); 50-250w, 40Hz-20K; 89db sensitive. Current sub is Polk PSW350, a 150W powered amp. Thinking of getting a HSU VTF MK-2 as a second unit since the store is only few miles away from my house. I have been contemplating b/c room size is only 12'X13', and I need to cough out another $500+tax, and not sure if 2 subs would drive my neighors crazy, which is the opposite of what these posts have stated, i.e. 2 subs should be less boomy as sound and dynamic range or sound freqency should improve. There is a 30 day trial, but you all know what happen when I carry home that heavy sucker with many rave reviews. That is why I want to remain objective, not bias, and listen to your valuable advice. Thank you all for reading. Any input is greatly appreciated.
Lej1447- I use two subs from one dedicated subout and split with a Y from the receiver, as well as a y on each sub cable to input to BOTH r and L inputs to each sub. I stack mine and I have a somewhat small room which enables me to do this. I am still tweaking but can make some brief comments on a much lengthier topic; Stacked subs give me more DB at the lowest extension of the sub. Splitting the signal of course allows a lower gain to be used on each sub for same SPL. Separating the subs can indeed "clean up" the bass, but also can easily reduce the volume.

I have a fair amount of tweaking left to do but I am leaning towards one sub for music and two for HT and I like being able to do that frankly.
I consider the subwoofer to be an integral part of the speaker system, just like the woofer, midrange, and tweeter. The fact that it happens to be in a different enclosure is a detail. Accordingly, I think that each main speaker deserves its own subwoofer, colocated with the main speaker, and driven by the LF signal component of the particular channel (not a mono SW mix). Thus, for my multichannel rig I have three SW (for the fronts) and will some day get around to installing SW for the rears. In my view the main function of the SW is to avoid extreme excursions of the main speaker woofer cone (or planar diaphram) so that the main speaker can do a better job on the upper bass.
Let me second the post by Exertfluffer.

Exertfluffer is absolutely correct - that the use of dual
subwoofers can give you better, smoother bass.

However, that is only true if you know what you are doing during
the setup.

With dual subwoofers, you can get phase cancellation, and
comb filtering - and really create a very peaky and uneven
bass response in your room.

If you understand acoustics - by all means - go with dual

If you don't understand acoustics - you run the risk of
creating a very poor soundfield in the bass. Setup of a
single subwoofer is far less problematic.

Dr. Gregory Greenman