[bpape]

Early reflections from the main 3 speakers are definitely undesirable. In the rear, it's not AS critical since you want a non-localizable 'soundstage'. In multi-channel, we always treat the front and rear differently. We always kill the front wall completely but never kill the rear wall completely.

This is not to say that there is not comb-filtering, there is. It's not to say that it doesn't have an impact on frequency response, it does. What it is, is a tradeoff. One can have no comb filtering for the rear by creating an RFZ for all of those too - but at the expense of the diffuse soundstage that is desirable.

It's a lesser of 2 evils and most won't lose the soundfield envelopment and be able to pinpoint their surrounds to save a bit of frequency response abberations. If you stop and think about it, diffusion can cause some of the same issues due to out of time arrivals and some cancellations in the wells but the effect it gives is still more desirable than the flat wall. Same kind of trade off.

And no, before someone jumps on me about diffusion and specular reflections being the same thing, they're not. They can just yield some of the same kinds of effects. It's all in what you're trying to accomplish. If I can let part of the room work for me instead of deadening even more of the mid and high frequencies, I'll do that. If we were to plot every reflection point for all 7 speakers for all seats in a room, almost every single surface in the room would be 90+ % covered with absorbtion. Then you've shot your balanced target decay time curve.

Just my 2 cents.

Bryan