sub positioning..

Best (and simplest) technique I ever came across is: Put the sub at your listening position, then move around the room listening for the spot(s) where you get the cleanest bass. Then put the sub in that (or one of those) spot(s).

Yeah, what NsGarch said...
You do, however, need to make sure proper phase is considered, relative to other speakers/seating possition.

With Jim Thiel's subs, it doesn't matter because his system allows you to dial in their placement relative to the room boundaries, then you're done. Voila, perfect integration with your mains.

Placement won't affect the sound stage as long as the sub is properly calibrated (use an SPL meter), you're using a low enough (< ~100Hz) cross-over frequency, the cross-over slope is steep enough (should be 24dB/octave low-pass), your sub-woofer doesn't have too much distortion, and you aren't creating any rattles.

Placement will affect the sub's frequency response and output level. Placements which produce higher SPLs for a given input will obviously have higher maximum output and produce less distortion for a given output level.

If you cannot delay the signal to the nearer of the sub and main speakers the sub placement will also affect how it integrates with the mains in the cross-over region.

Drew,

You kind of lost me at placement.....

Placing any sub or subs is very difficult. If you want the best from any sub and system you need someone with a spectrum analyzer to find the correct location. Two subs are actually easier to place than one and at least for music sound much better. I've read many of the Audiogon threads and info published on the web and tried most of the schemes on my own but was never satisfied until a pro helped set them up. Now I would not trade my Revel Sub 30s for anything, but before I serioiusly had my doubts and thought I'd made a big mistake. Mine are placed at the midpoints of the sidewalls. It cost quite a bit to get the cables to hook them up but the sound was brought up several levels once this was done.

sgr,

oh, okay. I pick up alot on on the gon but had no idea what an spl was...thanks..I was thinking of getting another sub but there is a whole list of things before that. thanks for the info...

dude, your system is something else...

Thanks for the kind words. Here are a couple of other thoughts concerning subs and main speakers. Adding subs to your system can take it to whole new leve. First I have eliminated the super low bass info by crossing the Subs and Salons at 80hz. This eliminates many distortions throughout the frequencies. This alone cleaned up the midrange and imaging quite spectacularly. Another benefit for using subs with any full range system is that it almost impossible to position your mains in the best position for bass, imaging, midrange, treble, etc. So this way I could use my Salons as the ultimate satellites, and place the Sub 30s extactly where they were needed to correct the mode problems in the room, something that apparently no amount of equalization can do by itself.
As a result, while my Salons or probably any well recognized floor stander sounded good, with proper sub placement the sound really reached another level maybe even several levels up. I marvel at what I was missing each time I listen to one of my favorite cuts.

I certainly didn't understand this myself until just recently when Gerry LeMay from QUEST helped me set the system up properly.
To me that is the fun of this hobby that there is always something new to learn and try.
Sgr

Alignment of all the voice coils involved is crucial to proper wave launch and soundstage enhancement.Tom