My folks came and visited for Thanksgiving, and again at New Years. Now they want to set up a home theater after seeing how much fun "surround sound" adds to the movie-watching experience. They like my EBS Shiva, but don't have quite enough room for 1 big sub. They DO have enough room for two smaller (3 cubic feet each) subs, though. The placement of these subs would be under the left and right main speakers. They would NOT be "stereo subs", however. My concern is that there will be cancellation issues for the person sitting on Couch 2. If someone else sat on Couch 2 (even closer to the TV/subs), I fear it would be even worse for him/her. I thought about firing up LspCAD and looking at phase interaction between drivers placed on a baffle the width of the living room, but that's not really what it's designed for. I'm sure there could be some way to measure the distance between each sub and the seating position, and figure out what frequencies will cancel by using some ratio between distance and frequency-wavelength. How exactly would I perform this calculation? Would a difference of 1/4th wavelength be the maximum allowable difference? How long are wavelengths at various subwoofer frequencies, anyway? I hope I've explained my question clearly enough.