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Diffusion vs. Sound Absorption views

I have Spatial Audio M4 Triode Master open baffle speaker in my listening room.  I have sound treatment behind the top of the speakers with sound absorption panels hung on the wall and an Aurelex foam panel down to the floor. 

It was recently brought to my attention that sound diffusion panels behind the speakers might yield an improvement in SQ over the sound absorption panels.  The advice I got is that OB speakers benefit more from rear wall sound treatment with diffusion rather than absorption.  I put the issue to you learned folks for advice.  Thanks. 
whitestix
firstnot's avatar
firstnot
248 posts
 
Since you have Spatials, why not contact Clayton Shaw, owner,
and ask the source. He is a person very willing to share. Overall
I understand absorption be best used to stop early reflections,
ie in front of speakers on side walls and ceiling. Diffusion best on front and back walls.
ptss
1,964 posts
 
Essentially 
Diffusion everywhere, particularly front and back walls and ceiling in your case. 
Absorption only where benefits are obvious through experimentation 
mwatsme's avatar
mwatsme
185 posts
 
How do you know when panels are needed? I'm interested in the topic, but don't notice a problem with Golden Ear Triton 3+ about a foot from front wall and 6" from side walls. If it already sounds good don't mess with it? Tinker for better sound? Or is there some measuring equipment for this? 
snapsc
674 posts
 
Conventionally, diffusion improves perceived ambiance while absorption improves imaging.


I suspect that the answer is somewhat dependent on the distance from the rear of the OB loudspeaker to the rear wall.  Why, if the speaker is too close, then there is much more of a chance of the out of phase wave interfering with the sound coming off the front...so absorption should help.Here is a brief but interesting article:

http://www.gikacoustics.com/speaker-boundary-interference-response-sbir/


I think that you can "simulate" the effect of diffusion by moving the panels out from the wall another 2-3' (not that you are going to leave them that way) which will then give you a different combination of direct sound, reflected sound and absorbed sound.
geoffkait's avatar
geoffkait
23,365 posts
 
What’s really needed is a test tone such as found on test CDs, say 315 Hz, which works fine, and an SPL meter. Then, determine locations in the room where sound pressure peaks 6 dB or higher than the average sound pressure in the room at moderately high loudness. Those locations are generally where acoustic devices - panels, resonators, etc. - should be placed. Without a method for placing acoustic treatments it’s like shooting blanks in the dark. As the system evolves you should find that the locations of acoustic devices can change along with the system changes. Ditto speaker locations. It’s a fluid situation.
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