Planar Speakers and Diffusors

I've used planar type speakers for over 40 years, so I'm very aware of the issues with setup and room. Currently using Maggie 1.7i's in a 22' x 16' room with a 9' ceiling. generally it sounds very good. I also have a large(ish) TV (65") in between the speakers. The TV being there is a BIG influence on the sound stage and image focus. I have a very thick soft wool type blacket, doubled over, which I drape over the TV when critical listening, and when used the result is not subtle. I've demoed it several times to audiophile friends and they all hear the improvement it brings, instantly.

My theory is that the sound bounces off the wall behind me, then forward to the TV and then back to me, and the 'blanket' reduces that secondary reflection so one hears the direct sound from the speakers more prominently. It works, and very well, for me.

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 

@ozzy 

I know nothing of planar speakers as I never used any. However I can easily point to the gigantic TV screen between your speakers as a major reflection contributor. You need to at least cover it with some type of 100% wool covering while listening to your stereo. Diffusers behind the speakers would have a very small effect considering any reflection from the back wall will go straight back to the speakers as they are not angled/toed-in at all. The problem is compounded by the fact that you basically have no space between the TV and ceiling. It's in effect like a glass wall. Plus if you follow Gik's directions, I believe the Q7d are recommended for the back wall and back of sidewalls. I spent a fair amount of time and money on acoustic treatment so I learned a thing or two over the last 5 years. Best of luck with that beautiful audio equipment.

Bottom line you would be better off diffusing the back wall with the Q7ds imo.

Hi Ozzy,

I have been using Line source Dipoles (planars) since 1978. I owned Apogee Divas for 6 years. I currently use Sound Labs ESLs. 

You are headed in the right direction, but someone fed you the wrong information. 

Line source dipoles radiate sound in a "flat" figure 8 pattern. By "flat" I mean there is no sound radiated up or down. In your case the lines source characteristic ends at about 250 Hz. Middle C is 256 hz. For the best imaging you need sound absorption behind the speakers. You want to kill the back wave as much as possible. Diffusers are simply going to increase the number of early reflections, confusing the image more. I use 4" acoustic tile behind the speakers. It is very effective above 250 Hz and dirt cheap. It also looks cool if you get the pattern right. You can get it on Amazon.

At first you might think the sound has become duller, less air, whatever. But, if you are paying attention, voices now hang, well defined in space. Any hint if sibilance behind female voices is greatly reduced or gone altogether. Everything is in better focus. The third dimension becomes palpable. The glare is gone. If you take the tile down you will not believe what you had been listening too!

The problem below 250 Hz is much more difficult. As the wavelengths get longer they are harder to stop or deflect. The wavelength of 250 Hz is about 1 meter. 

Another issue with planar speakers, especially full range or two way types is they HATE making bass. They will do it but it distorts everything else the driver is doing and wastes a lot of power. You can lower distortion and increase your head room by as much as 10 dB by adding two subwoofers and a two way crossover with digital bass management. People think it is difficult to match subs to planars. Not true at all if you do it correctly. It is tougher, but it can be done to great effect. You have to cross up around 100 Hz with a very steep slope of at least 8th order and match the launch time of all the drivers. This can only be done digitally. it is like adding a turbocharger to your car. Two Martin Logan Balanced Force 212s and a DEQX Pre 4 processor would be amazing.