B1 Bass Module / Walls
Should I place the B1 Bass Modules on the back wall?
It depends on the wall construction. Most drywall will reinforce midbass (like 100-250 Hz) and let the deeper octave or so pass right on thru giving you little reinforcement from reflection. So if you push your bass boxes up against the wall, you'll tend to get a lot of midbass with a typical drywall-constructed wall. And, yeah, then it will be muddy. Most walls don't reflect sound uniformly with frequency, so you get a change in spectrum you probably don't want no matter what. One possible exception to this is, say, 6" thick concrete with a 1/4" thick lining of steel. Oh, and don't take my word for it either. Do it yourself and see what you hear. Also, aiming the individual bass boxes won't have much effect as they are so much smaller than the wavelengths they are producing that they are virtually omni. For instance, a 125Hz wavelength is on the order of 8 feet. A pair of b1's on each side of your ps1 will give you a hotter midbass down the middle and not so off to the side. Here, you've essentially made a crude bass array. So, my experience with all this tells me that the most consistent way to set the bass up, gig to gig, is to lump the bass boxes together and keep them away from the walls. You won't get the extra bass boost from the walls, but if you did, it wouldn't be wideband. I think you'll always do better not asking the wall to help. You know what they say about free help (you get what you pay for). This works for bass players, dj's and so on.
Trying to improve bass by placing speakers in various locations is like playing a giant whack-a-mole game, if you get the drift.
Water Bed Analogy
The water bed analogy is the same as the whack-a-mole one: push down here and it pops up over there, on and on and on (and on and on).
We received a fantastic and crystal-clear demonstration of all this (bass and room modes) out at the Hidden Barn/Big Sur from My Man Chris Ickler. Ken and I did the Vanna White Replica, moving an active B1 all over the room to Chris' instructions, including in the corner and against the wall. As we did this, the "class" walked all over the room and noted that it just changed things and moved them around the room, didn't make anything "better", except maybe at one position. You can easily be fooled by changing things, hear it as "better" where you are located and not know what's going on in the rest of the room.
Of course, if the "improvement" is in the player's position, the player might have a better experience and thus deliver a better performance, even if he or she is getting a different bass experience than the audience (this always seems to be true anyway, at least for some of the audience). And we all know that a great performance always transcends all media. Witness "Good Golly Miss Molly" on a bad mono car radio with shredded speaker cones and road/wind noise coming in through the open windows. It still puts you (one) into orbit.
So, anyway, try it and note what you hear (um, not "see what you hear")