Originally Posted by Cooksons
Lastly, it seems like an easy way to avoid compensating for cascading delays in a "cascading DDRC-88A/BM" setup would be to perform BM in the AV8805 and run all channels through the two 88As unmixed.
That's the easiest way to deal with your set-up. Connect all speakers to the two 88A units and Dirac them. They will be time aligned and level matched, as well as EQ'd over their entire range. Then do an Audyssey calibration on your 8805.
Since Dirac already calibrated all your speakers, they will all appear to Audyssey the same distance away and the same level. IF there is any difference in latency between the two 88A units, Audyssey delays will compensate for that. Then turn off Audyssey EQ, leaving only the delay & level settings in place on your 8805.
Doing bass management on your 8805 means that bass from ALL channels will be routed to the subwoofer output. With two 88A units, how do you get the bass from the channels in one unit to the subwoofer outputs on the other unit? Also, since Dirac EQ'd the full range of your speakers, you are free to adjust crossover settings on your 8805 whenever you want.
It seems like I could even independently route the 2 sub outputs of the AV8805 through 2 channels on an 88A and then out to the subs.
Generally not a good idea. You never listen to each of your subs separately, so you should not EQ them separately. One of the reasons to use multiple subs is because they can fill in each other's peaks & dips. Since you're always listening to the interaction of your subs, it makes more sense to EQ their interaction (i.e., connect ALL your subs to one Dirac channel).
If you're willing to spend the time doing subwoofer optimization (adjusting level, phase and EQ on each sub to improve their interaction) before Dirac does it's EQ, then that can be helpful. Keep in mind that there can be thousands of combinations of level, phase and EQ between a pair of subs, so trying every one to find the best combination can take years.