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Absorb or Diffuse Behind Listening Position?

Hey All. Starting to finally treat my listening room. My listening position is up against the rear wall (head probably being spaced about 12" from the wall when sitting down). I’m putting 2’x4’x2" absorbing panels behind the speakers, but what should I choose for behind the listening position? Diffusion or absorption?

There are al lot of windows in the room, with horizontal louvered shades which act as pretty decent diffusion; and a big built-in bookshelf on one side wall also helping with diffusion. On either side of the wall behind the listening position are a pair of glass French doors, untreated at this point, and the room sounds a lot better when they are left open to the big room on the other side of the wall. I haven’t tackled the ceiling yet either. Thanks!
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bdp24's avatar
bdp24
9,787 posts
 

For a diffuser to work, it has to be a "certain" distance from the listener's ears. I put certain in quotes because the distance is frequency determined. A Google search will lead you to the related data, but start with the YouTube videos posted by Acoustic Fields.

Your ears being only 12" from the rear wall (or even twice that), I would say diffusion is out. Simple Owens Corning 703 panels (covered in material of your choice) is a good choice, the 703 being what almost all commercial makers of absorbers (GIK, ASC, etc.) use.

mijostyn's avatar
mijostyn
8,570 posts
 
summadoggie, that is one of the worst listening positions you could have for a number of reasons. You can use absorbers behind you but that will do nothing for the bass which will be exaggerated by up to 6 dB.  You need to pull yourself at least three feet away from the wall. The best listening position is always somewhere towards the middle of the room. 
rodman99999
6,123 posts
 
What mijostyn said +1, but for the middle of the room position.    My present seat is right at 35% of room length, from the back wall, with Auralex absorption and LENRDs behind me.    Diffusion behind the speakers.    Some tips: (http://arqen.com/acoustics-101/room-setup-speaker-placement/)     and: (https://www.gikacoustics.com/basics-room-setup-acoustic-panels-bass-traps/)
mike_in_nc
1,147 posts
 
I think a combination of absorption and fine-grained scattering would probably give best results. One option is the ASC Matrix Panel (as mentioned ty @asctim above). Based on the quality of their other products (I have plenty), I’m sure it’s a great product.

Another option is some 4" thick BAD panels from RPG. I used those in a similar situation and was quite satisfied. There undoubtedly are other similar products on the market.

The objective is that the wall behind you disappears acoustically, neither giving a strong echo (reflection) nor a dead zone, as a pure absorber would create.
arion's avatar
arion
160 posts
 
Having the listening position against the back wall is not ideal. I assume the OP has no other possible listening position available or perhaps it's a multi-purpose room and there must be a compromise. With that listening position you definitely don't want any reflective surfaces behind you. Diffusers do reflect sound but in a scattered pattern. It's easy to understand why sitting close to a real diffuser isn't ideal. Speak into one that is about 12 inches away and you will know.

What we have recommended before is to use broadband absorbers about 4 to 5 feet wide behind the listening position. Flanking the absorbers can be left reflective but diffusion is better.

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