One Magix think is ever ever so slightly a bit of absorption. I had a guy who had me hang a shear four inches off the wall behind the speakers the material what to be a shear with holes in it. And wanted enough so I could change where there were more folds in it. The end results were just enough so the sound stage expanded and everything cleared up just a bit more an increase in resolution. I had a set of Maggie 3.3 back then and they were actively biamped. Also had diffusion behind the curtain and at the reflexion points plus behind the chair. The diffusion panels were approximately 2 x4 feet. Had them all on stands about 16 inches high. At the first reflection point had a small amount of suction in the diffusion panels. In that room with that setup I personally have never heard any system come close to the sound stage I had. I personally like what I have now better but the wonderous sound stage was fun to show off. The tonal balance was basically perfect what was missing was the fun and beauty part.it was boring In comparison to any of my current setups.
Regards