Smoother bass by running woofer out of phase?

At least one researcher in the field of subwoofer/room interaction recommends using two subwoofers operated 90 degrees out-of-phase with each other. I have used subs operated 180 degrees out of phase with each other at times. It offends one's notion of order and symmetry but can sound very good.

You may even get in increased sense of spaciousness from the out-of-phase configuration. And the bass isn't reduced as much as you would have thought, is it?

Duke

The ear literally responds slowly at very low frequencies. We cannot hear less than 1 cycle at very low frequencies, and by the time 1 cycle has reached us enough time has elaped that we're past the direct sound and into the reverberant sound. Unfortunately I don't know the (probably fuzzy) cut-off point for this phenomenon. But it can be said that from the standpoint of psychoacoustics, there is no "direct sound" in the deep bass; at least not in the size rooms we typically have at home.

The increase is spaciousness is probably somewhat artificial because very few recordings actually have stereo information below 80 Hz. The ear interprets a low-frequency phase difference at each ear as a sign of very large acoustic space, and that is what is being synthesized by reversing the phase of one of the woofers. Out-of-phase subwoofers placed to the extreme left and right of the listening position will maximize the interaural phase difference and hence the simulated sense of spaciousness. David Griesinger, inventor of the Lexicon processor, advocates this technique.

Duke
dealer/manufacturer

One other comment relative to in-room bass smoothness: Note that fullrange dipoles have smoother in-room bass than monopoles (James M. Kates, "Dipole Loudspeaker Response in Listening Rooms", JAES May 2002). A single dipole may be thought of as two monopoles out of phase with each other. I think there's some merit to the idea of playing around with driver phase in the deep bass region.