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Higher SBIR problems can be nicely addressed with staggered placement of the woofer, which is hinted at here but not explicitly explained with placement near one boundary. In other words, you can very much smooth the common satellite-type lower-midrange notch (in the octave below middle C — NOT the bass!) with placement 2′ x 3′ x 4′ or 5′ from the near corner. The worst case of course is identical distances from the near corner. This solution to the Allison effect, as it was long known well before SBIR, is effective. Otherwise, yes, it can indeed be partly EQed out (filled in), since this is a room-power notch (resulting from changed air pressure on the cone surface from the reflected impedances) is rather more location-invariant than not, unlike room resonances.

It is crucial furthermore to understand that this is NOT LF. Observe the power suckout graph above with the notch at around 130Hz. That’s the C below middle C. Go to a piano and play it and see if anyone would label that bass. It is common for the Allison effect to lie higher than that, as well.

It might also be useful to go more into the ear’s integration, how in domestic rooms there is no such thing as direct sound below a very high frequency (well above middle C). Just calculate the wavelengths, periods, and time in milliseconds for all of the combo sound to get to your integrating ear when seated a few feet from the speaker, and it should become clear. Keep this in mind when someone speaker of ‘direct’ sound at say 220Hz. How many cycles have occurred before it registers at your ear, which is an averaging detector that requires considerable time to make its determinations?

Finally, you want to distinguish in this analysis among (1) coherent reflection summing (LF, sub placement in corner, all good, maximally driving room resonances, w/ possible LF treatment a la Winer for audibly bad situations); (2) much higher (midrange and treble) summing where it does not matter and the ear does not care except when a tweeter is near a boundary and there results a nasty peak; and (3) this lower midrange Allison effect area in between, where the wavelengths are similar to the distances to the boundaries.

Studying the extensive Allison scientific writings on this physical phenomenon is enlightening for anyone placing or designing loudspeaker systems.