Do Diffusors Work Well on Low Ceiling?

[ruanddu]

I have 7ft ceilings in my music room and currently have it covered with mostly Auralex 2 inch foam 2x4 sheets. The room is sounding too dead. I am curious if diffusors would work well on the ceiling, over the mix position? Or is the ceiling too low? Thanks much, Josh

[Ethan Winer]

I wouldn't use diffusors on a low ceiling. As for your room sounding too dead, if the room is very small that's probably for the best. Since you didn't say how large your room is I won't even guess at what to suggest.

--Ethan

[ruanddu]

Thanks, Ethan.

The room is about 16x15ft.

Would you mind explaining why diffusion isn't a good idea on a low ceiling?

Thanks again,
Josh

[SAC]

Depending upon the type of diffusion used, you can potentially be within the near-field of the diffusor.

In the near-field you experience the response of each component 'well/element' reflection individually rather than experiencing the superposed response of the various reflections as a coherent unified diffuse sound-field that does not vary with distance.

[gremmy]

You can sit closer to some type of diffusors than others. I believe I read in an RPG patent document that the distance required is as follows (in order from most to least).

1) 1D QRD Diffuser
2) 2D QRD Diffuser (or possibly PRD)
3) 1D Binary Amplitude Phase Grating
4) 2D Binary Amplitude Phase Grating

2D Bad Panels require the least amount of distance, so I have no doubt that you could use these even on a fairly low ceiling, especially since they absorb about 50% of the energy within the range of frequencies that they diffuse.

In my Home Theater, I have about 8 feet inbetween the 1D QRDs on my back wall and my seating position, but I will be adding bad panels above/behind the seating position on the ceiling, and I expect distance will be fine.

[Ethan Winer]

Originally Posted by ruanddu

Would you mind explaining why diffusion isn't a good idea on a low ceiling?

Mostly because that puts reflections so close to overhead microphones. However, being close to diffusion isn't always bad as you can hear here:

All About Diffusion

If you could easily switch from diffusion to absorption when recording to decide which sounds best for a given session, that'd be great. But this probably is not practical. If you use absorption it's guaranteed to sound okay.

--Ethan

[Glenn Kuras]

SAC gave you the right answer. The rule of thumb is for ever 1" of depth of a diffusor you want to be 1' from from it. Though that really is only a "rule of thumb".