John,
You'll certainly get some enhancement of bass output if you put the M22s up against the wall on the stands. As to how much, I'll check that with Ian. I'm curious myself about the mid-wall position of the M22s on brackets and whether greater bass reinforcement occurs because of the larger wall surface acting as boundary enhancement.
Keep in mind, too, that the bass reinforcement may not be entirely even over the lower octaves, but in my listening tests in the Axiom room, I did not hear uneven bass extension. That may vary, of course, depending on the listener position in the room and, I suspect, the total area of the surface behind the speaker that is bracket-mounted.
