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What Frequency Range Should I Diffuse ?
Posts: 1
April 4, 2019 - 4:50 pm


Hi, I have made several spectral measurements in my mixing room and I have noticed the same problem. I Have a dip from 600hz to 2khz ranging from -1db to -4db. Should I make my diffusers in that range so I can reinforce those attenuated frequency’s by diffusing them? Let’s say i’m going to make a QRD diffuser that diffuses 700hz and cuts off at 2000hz. does it seem right ?

thank you for your videos !

Posts: 570
April 6, 2019 - 11:17 am


Diffusion will not assist you with peaks and troughs in frequency response. It will actually make them worse. You must use broadband absorption to treat the issues.

Posts: 6
January 13, 2020 - 1:14 pm



Are you sure about this? It seems to me that nadeau777 was on the right path with his suggestion.

As far as i know, the very main purpose of phase grating is to keep the energy within the room without disturbing the frequency response, by spreading the energy out in time.

Posts: 570
January 15, 2020 - 10:14 am

S, Diffusers can not add anything to the room response other than higher Rt-60 times.

Posts: 6
January 17, 2020 - 11:02 am


I will have to respectfully disagree with you there Dennis. Specular reflection from one plane will cause peaks and dips in the frequency response, because all the energy will arrive with a specific time delay in respect to the source. Depending on this time delay, some frequencies will cause destructive and some will cause constructive interference, causing peaks and dips.

A properly designed and built QRD will spread that same energy out in time, this will create a more even interference-pattern. There will no longer be certain frequencies where all the reflected energy has a perfect 180deg phase shift caused by a single time delay.

Posts: 8
November 11, 2021 - 11:37 am


Hi Skogs, so is the diffuser phase shifting the troublesome frequencies/band so they are “uncancelled”? Just trying to get my head around Nadeau777’s problem.

Posts: 570
November 11, 2021 - 12:52 pm

What is the issue?

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