Ralph's (atmasphere) advice matches my experience with planar loudspeakers. The common wisdom for dipole/wall spacing is at least 3' from the front wall (behind the speakers), but that is incorrect. As Ralph said, we want the rear wave to reach our ears no less than 10ms after that from the front of the speaker. Any less than that, and the rear wave in effect sounds like a smearing of the front signal, rather than a separate event. As sound travels at approximately 1' per ms, that requires the dipole be 5' from the wall (5'/ms from speaker to wall, 5'/ms from that wall back to the speaker).
And diffusers on that wall can help disperse rather than absorb the rear wave, a good thing if your room is on the warm side. Absorption on that wall will reduce the amount of life and energy the speaker produces, which can be good if your room is too live, and perhaps cold/bright.
And diffusers on that wall can help disperse rather than absorb the rear wave, a good thing if your room is on the warm side. Absorption on that wall will reduce the amount of life and energy the speaker produces, which can be good if your room is too live, and perhaps cold/bright.