Dampining The Rear Of A Planer Speaker?

I have a pair of Eminent Tech LFT-8, can the sound be improved by adding sound absorption to the rear of the ribbons. If so what material would be best, and should it be placed tight against the speaker?
Try adjusting toe-in and rear/side wall distance to determine the optimal placement for soundstaging prior to using any acoustic treatment. You may want to try diffusion on the wall behind the speakers. Auralex makes several affordable alternatives. This may create a more spacious image. Absorption will probably result in excess bass unless full-range absorption is used and that is usually very bulky and expensive. Acoustic treatments directly on the rear of the drivers will change their physical operation in unpredictable ways and will almost certainly degrade performance. Check with Eminent Technology before venturing down that path. Good luck!
Agree, call Bruce Thigpen at ET....he is a pleasure to talk with, if anything you want to just scatter or diffuse the back wave but its not made for cloe absorbtion, if thats what you need to do look into VMPS as an example of a hybrid planer sealed box speaker.
I had planars for many years. The critical problem is rear and side spacing. I started with a calculation. I would measure the room and try to find a series of distances that made odd fractions. such as 1/7 or 2/7, 1/5 etc for back to speaker and side to side. And go from there. planar speakers are amost always best well out into the room, 3 feet is the minimum.