bang, that's pretty much how I understand the different types of filters to work, too. I think you're right about the output phase shifts being coherent between the two resulting streams. That isn't a problem when the stream is going to a standalone transducer, but when you have 7 streams potentially shifted to 4 different angles, then combined with a 5th stream into a sub out, what happens when the same signal is present on all 5 sources? I'd think it could get chopped up pretty good.

Another problem with phase shifting controls (adjustments) is that as the frequency goes to zero, the delay time goes to infinity. They'd have build in an absolute high-pass filter and stop quoting response down to DC.

I wonder whether the 'distance' configuration might be used to tweak bass stream phases? I wonder how you'd measure it without a 4-channel scope?