>>Does absorbing panels, traps and diffusers tend to flatten the sound as these shutters seem to be doing?
Sort of, but in your case I think the issue is that you need to recalibrate by a few dB when opening and closing the shutters, or at least calibrate with them set to whatever you use when listening. I noticed that between my left and right surrounds (M2s right now; my QS8s are out for extended audition) I had to bump one side up by 4 or 5 dB because it was in the open while the other was a couple of feet from a wall.
Randy, the good news is that you have a new degree of freedom -- you can experiment with changing your room acoustics by moving the pool table around
