Distributed Bass Array configuration

@millercarbon  - I trust that my joking exchange about "experts" was not something you took personally. It surely was not aimed at any particular person.
I appreciate your contributions as well as those of others.

Of course not. Especially not since I agree, at least in my disdain for experts, and credentialism in general.

What gets me is what I said- asking very specifically for the advice of people with a DBA. But then when you get it you go with the advice of someone who not only has no DBA, but knows nothing about them, and in fact runs around threads like this where his lack of knowledge is expressly not requested, and spreads his bad advice as if he actually knows what he's talking about. 

I had a friend, an expert fisherman. This guy knows everything about everything when it comes to fishing. When another friend was looking for advice on a boat I naturally referred him to my fisherman guy. Who said sorry Chuck, I am not gonna help him. Why, Larry? Nobody knows more about this than you. "Because I don't want to waste my time" and then proceeded to tell me all about people he advised who then ignored everything he said. So he doesn't do that any more.

Me, I am more selective. No hard feelings. No more help either. I'm sure you understand.

Its not just me by the way. Read the thread. You disrespect Tim as well. So basically the only two guys to give you what you ask for you disregard and disrespect. 

I hope a sub with a continuous phase control will work well enough.

Nope.

"All-Pass phase controls operate at only a single frequency with varying degrees of shift across the passband."

see http://www.ielogical.com/assets/SubTerrBlues/PhaseControl.png at  ieLogical SubterraneanHomesickBlues for an image of how a continuous phase control functions.

Mike_in_nc, if you get an acoustic measurement mic and program like this one, https://www.parts-express.com/Dayton-Audio-OmniMic-V2-Acoustic-Measurement-System-390-792
You can measure group delays and frequency response. You should be able to adjust your subs perfectly.  I assume with their location you are using a low crossover point. What are you using for your main speakers?
Where you place them depends on your main speakers. Subs always perform best in corners. They are up to 9 dB more efficient which means much less distortion. For point source main speakers four subs in four corners would be ideal but two in corners and two right up against side walls would be a close second. A sub should never be in the middle of the room. That is like running your outboard motor out of water. For maximum dynamics you have to be able to adjust delays so the sound from your subs gets to the listening position at exactly the same time and in phase with the sound from your main speakers. This requires digital bass management. Are you still using a digital crossover? What happened to the 2.2X? Yes, Apogees have a reputation they do not deserve. They were capable of amazing sound on occasion but their fragility disqualifies them. Magnepans are a much better design from a reliability standpoint and if a ribbon tweeter blows (which they do rather frequently) Magnepan has a great tweeter replacement program and if you can use a screw driver you can change the tweeter. Apogee went belly up for a reason. 

Don't know if you are familiar with  Earl Geddes?

You should check him out and read the several white papers regarding subs and other stuff

http://www.gedlee.com/Papers/papers.aspx