forward steered arrays -- better than dipole?

[batdorf9]

I was reading various JBL tech notes recently and came across this: Tech Note: Volume #1, #28: Forward Steered Arrays in Precision Directivity™ Speaker Systems

Here's my attempt to summarize the idea:
The basic idea is to use multiple drivers offset along the intended direction of aiming and then delay (using a dsp device) the signal of the forward drivers back such that the waves align along the aiming axis. The proposed advantage is that you get cancellation off-axis (more at some frequencies than others).

This makes sense in large pro-sound applications, and I'm curious as to whether it may also make sense in a typical sized home listening room.

For my own application, my room is 20ft x 20ft (6m x 6m) which leads to a particularly annoying room mode at 28Hz (1/2 wavelength of 28Hz is 6m). These modes are even more annoying because there doesn't seem to be any sound absorbers (rigid fiberglass, etc.) that can absorb/dampen such LF. I'm tempted to position one sub against the front wall, then another sub near the middle of the room. I've got a spare channel on my DSP, so I can use that to delay the signal to the sub in the middle of the room. If I understand the JBL paper correctly, you get the most cancellation off-axis at the frequency where 1/4 wavelength of the frequency is the spacing (3m for the most cancellation at 28Hz in my case).

The potential advantage I see of this over dipole bass is that there is no need (or at least significantly less need) to boost low frequencies to compensate for the dipole corner frequency, which would lead to significantly higher efficiency and likely to reduced distortion (less excursion required for same LF output).

Am I missing something here? Or is this a good idea?

I may give this a whirl today if I find the time.


- Robert