Distributed Bass Array configuration

One thing to keep in mind: if you are using a sub (or four) with---I would certainly hope ;-) ---a low-pass filtered signal as its/their source, well, what is the slope of that filter? If only 6dB/octave (1st-order, as with the Vandersteen subs), that sub reproducing a, say, 80Hz signal, will be reproducing 160Hz (an octave higher) at only 12dB down. Who thinks a 160Hz wave cannot be located in space? How about 320hZ (24dB down)? Naturally a higher-order filter will change those figures.

If you run your sub(s) in mono, that mono output will extend further up in frequency that the frequency at which the x/o is set, the degree to which is determined by the slope of the filter. It is for that reason that some prefer employing higher-order filters (both high-pass and low) to integrate speakers and subs.

Brian Ding includes a continuously-variable 0-180 degree (0-16ms delay) Phase Control on his top-level Rythmik subs for a reason. If a loudspeaker is mated with a subwoofer or two---the speaker and sub(s) used with an electronic cross-over set to, say, 80Hz, the loudspeakers receiving a high pass-filtered signal, the sub(s) a low pass-one---if the loudspeaker and sub are reproducing an 80Hz signal in opposing polarities---creating a null at that frequency, the two will produce a combined frequency response with a deep notch centered at 80Hz. The Phase Control is provided to make possible getting the loudspeaker and sub in phase at 80Hz, thus avoiding the deep hole in frequency response centered at that frequency. This is loudspeaker design theory 101.

As for stereo bass in recordings: some music contains two---or even three---different basses being played simultaneously. Brian Wilson has an electric 4-string, an acoustic (upright) 4-string (both producing a bottom note---E---41 Hz in frequency), and a baritone 6-string all playing at the same time on some of The Beach Boys recordings. But Brian mixed to mono, one reason being he wanted to determine the balance between all instruments and voices, not leave it to the mercy of the hi-fi speakers and their placement.

But some recordings made in large churches, cathedrals, and music halls (Classical, mostly) are well-known to contain out-of phase low-frequency information between the two channels in a true stereo recording, caused by the long wavelengths created in large rooms. Left and right channel mics may received sound from the same sources at different times---the very definition of phase. The bottom note played on an organ fitted with a 32 ft. pipe produces a 16Hz tone! Recording engineers work hard to keep the sound of the room intact, which requires maintaining that out-of-phase information at low frequencies (you can read about it---it’s in the literature.). If your music collection contains such recordings, please respect the engineer’s work, and use your front subs in stereo pairs. Additional subs may be in mono.