What about the phase anomalies you and I happily live with, caused by dipole speakers where the rear radiation is 180 degrees out of phase with the front?
@lewm @mijostyn The reason any speaker with rear firing information should be at least 5 feet from the wall behind it has to do with how the ear processes near term reflections. When 5 feet from the wall behind the speaker the delay time is about 10ms. When the ear hears a sound, it makes a short term copy and looks for other examples in near term. If less than 10ms or so, the ear interprets similar examples as harshness (which is why side wall reflections have to be tamed), but if 10ms and over the ear can use it as echo location information, which means the sound stage of such speakers can be more palpable.
So I'd be unconcerned about 'phase anomalies' in this regard.