# Ideal Audio Dimensions Versus Diffuser



## aardvarcus (Oct 6, 2009)

Still in the planning stages of my HT, but I need to flesh out most of the design so I know exactly what sized space to leave in my basement for it when I build my house. (hopefully late summer/ early fall we can break ground)

How important is following a set of ideal audio dimensions if you have a ton of diffusion in your room? For example, if you were going to build a room to 1, 1.6, 2.33 ratio (roughly 8', 13', 19', exacts undetermined), but you decided to cover most of you back wall with one big diffuser, would it matter if you "stretched" the 2.33 on out larger and built a 1, 1.6, 2.XX room? Wouldn't the majority of the sound waves never make it to the 2.33 anyway, because the diffuser would stop most of them from actually touching the physical wall?

On a similar note, can you over diffuse a room? I know there are diminishing returns, but does it ever get worse? (Provided you have the appropriate amount of absorption already present.


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## MatrixDweller (Jul 24, 2007)

Diffusers deal mostly with higher frequencies. The ideal room dimensions will play better with low frequencies. Even huge bass traps (absorption) start to lose their effect under 80Hz. 

Sound is still going to bounce around but the room modes will be minimized by ideal dimensions so that you don't have as much constructive/destructive interference (peaks/nulls). You would still want absorption and diffusion to control echoes and improve reverberation time.


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## Dennis Erskine (May 29, 2010)

This whole business of "ideal room" dimensions is highly overrated. First, there are so many of them. Second, in smaller residential settings 6" will move you from "really, really good" to "awful". In reality, the room is not going to work that way. You will still have modal response issues to deal with, wall impedances will have a bigger impact (in small rooms) than dimensions, and the "things" you have to do to fix low frequency reponse issues will be the same regardless of the dimensions!

In a small room, following these "ideal dimensions", you can easily end up with a room with poor ergonomics, too big/small for your planned use, and still sounds horrible ... so, design the room to fit your needs, seating desires, picture size, speaker/amplifier/projector budget...draw a box around that size THEN work on the LF response strategy.


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## bpape (Sep 14, 2006)

I would agree completely with Dennis. There are no 'perfect' dimensions. What you want to do is to try to avoid particularly bad ones like a room that's 16x24 with an 8' ceiling.

As was previously stated, diffusion isn't going to reach anywhere near low enough to counteract any length related modal issues. Proper placement of seating and speakers will do MUCH more to help with smoothing response (along with proper treatments)

Bryan


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