I don't think I would pad the wall behind the speakers. The problem is you can only catch some of the frequencies and will most likely change the tonal balance of the speaker (making them seem dull, and bassy). But you could also try diffusors behind the speakers instead of a bare wall and bass traps in the corners. The diffusion may make the time delay longer (a good thing, in moderation) from the direct sound of the speakers and reflected sound off the front wall (behind the speakers) longer.
Does any one know what Magnepan recommends (if anything) behind the speakers?
Does any one know what Magnepan recommends (if anything) behind the speakers?