... and you are not likely to hear stereo in the bass under normal circumstances. Bass is low frequency which means long wavelength. The speed of sound in air is around 1000 feet per second so a 100 Hz tone has a wavelength of about 10 feet. (If you prefer another unit, feel free to convert to furlongs per fortnight or what you will.)
In practice in the home environment a single subwoofer crossed over in the 60-100 Hz range and placed anywhere in the room is likely to give the best bass. With two woofers placed reasonable distance apart, interference effects - even if they're driven with the same signal - will exacerbate the standing waves of the room. Room acoustics are at least consistent over time and frequency, varying only with position of the listener. "Stereo" interference varies with position *and* frequency.
Three quick comments on which experts may wish to expound.
1. Headphones have similar effect thanks to the dimensions of the head and the ears' phase sensitivity.
2. I believe there can be similar interferometry if stereo mikes are used for bass pickup.
3. If by "bass" you mean significantly higher frequencies, say from 200 Hz, then ignore the above.
Mike -- mrichter@xxxxxxx http://www.mrichter.com/