# Acoustic treatment: Yamaha Cinema DSP vs. physical diffusors - which is better?



## chrisreeves (Dec 15, 2014)

Hi all, first post here. I'm usually at the other major forum but due to lack of traction on this topic I thought I'd post here.

Anybody who reads up on acoustic treatment will encounter the commonly held assertion that acoustic diffusion is just as important as absorption when treating one's listening/theater room.

This got me thinking about DSP solutions. How effective could a DSP chip be in simulating diffusion to increase perceived room size? My room is relatively big by typical HT standards, but not huge (a little over 4,000 cubic feet - 25X19X9).

The most developed consumer solution is Yamaha's Cinema DSP - which in its current HD3 version uses 4 separate processing chips, has very adjustable parameters, and adds four extra "presence" speakers (no, i'm not sure how it is implemented when using Atmos).

Any feedback/experience with this? I'm asking because I'm in the early stages of room treatment. Currently I have four bass traps and two 2D QRD diffusers from GIK Acoustics. If I could handle the diffusion side of my room treatment with a couple extra speakers and a Yamaha receiver that would be preferable to covering my walls in QRD and skyline diffusers.

Thanks!


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## epwhitney1 (Dec 30, 2014)

Interesting idea. I am in the middle of acoustically treating my dedicated home theater room as well. Mine is small in comparison to yours at 14X15X9 ft but that's all the wife said I could have. I think you are on the right track with using extra speakers for diffusion but every room needs acoustical treatment no matter what. You will always have destructive and constructive interfering waves that will ultimately change the response of the room. Adding more speakers could even make it worse depending on how the waves interfere with each other. There are several room mode calculators mentioned here on HTS that may be able to help you.


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## AudiocRaver (Jun 6, 2012)

Agree this is an interesting idea. I have tried to simulate addition of specific delayed reflections to reinforce soundstage effects with no success, but you are talking about adding a little "air" to the room, effectively pushing back the walls a little. I see no reason it would not work. A little will go a long ways, you will probably be surprised at what a low level the added speakers run at to give the effect you want.

Not knowing what options you have to work with, you might start out setting an initial delay of 60 mS, just perceptible, then an RT60 of 0.5 sec, and start it at a level 20 dB down, creep it up a little at a time til you can just hear it.

Avoid adding at LF or HF, add just at mids and upper mids. Lows will just get muddy. Limit to the 500 to 4k range.


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