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Sound Diffuser Placement – How To Position A Sound Diffuser

Dennis Foley August 5, 2014 7 Comments

Today we’re going to talk about ideal sound diffuser placement and, more specifically, how and where to position your sound diffuser for your particular room usage. If you’ve been following my videos then you know that we prefer quadratic diffusion here at Acoustic Fields for two reasons:

1. It’s predictable and
2. it’s consistent in its performance.

So you can actually select the frequency response of the diffuser that you want to use for that particular room position and that’s what we’re going to talk about a little bit today.

Ideal sound diffuser placement positioning within your room?

Let’s stay with our quadratic diffuser, because with quadratic we have both vertical and horizontal diffusion capabilities. If the diffuser is vertically placed we know that it diffuses sound horizontally. If it’s horizontally placed we know it diffuses vertically.

So we have two out of three possible dimensions of sound within our room. So it’s a pretty powerful tool if you think about it.

So, what are we going to do with diffusers in our room and distances? What diffuser goes where? Where do you put it? On what Wall?

Let’s try to answer some of those questions.

We always have to get back to usage. What is the usage of the room? Because every room’s usage determines the positions of the sound diffusers.

Control rooms are different than critical listening rooms. Critical listening rooms are different than voice and live rooms and all of those rooms are vastly different than home theater. So the first thing we have to do is look at usage. What is the usage of the room? That’ll tell us what kind of diffusers to use and where to put them.
We’ll get to that a little bit later but let’s just get to some basic rules about diffusion and in terms of distances and I think it’ll help us understand.

DIY QD 13 Kit measurements

The image above shows a prime 13 diffuser (this is actually one of our DIY QD 13 sound diffuser kits which we sell here). Remember it’s prime 13 so it has twelve wells. A diffuser always has one well less than the prime number indicates. So if we break it down as I do in the below video, on the quarter wavelength depth of the prime 13, we see that we have about thirty four hundred as our high and two hundred and eighty two as our low.

This is the frequency we want to look at in order to determine the distance, how far away from our listening position it should be. So this is the key factor here in diffusers. What’s the lowest frequency the diffuser diffuses?

So does one diffuser fit all situations?

The short answer is no. You have to look at the distances from the wall surface where the diffuser is going to go to the seated position. So this is all critical to getting the maximum performance out of your diffuser.

So using our example of two hundred and eighty two cycles, if we divide the speed of sound by the frequency we get four feet, because these are our recorded wavelength depths. So four feet, is four feet away far enough for the wave form of two hundred and eighty two cycles to completely form within the room?

We know that all frequencies above that will be fully formed if we get two eighty two figured out. So is the four foot distance, is that enough to really realize the full impact of the diffuser?

There is no definite answer here. You won’t find a formula that you can calculate this. In our applications, we use this as a guideline and then we add fifty percent. So in our situation, six feet, the four feet plus another two, six-feet for two eighty two is a good starting distance. If you’re less than that in terms of distances in your room, we have to go with a lower level diffuser. Maybe a prime 11 or a prime 7.

So there’s applications for all the primes but we have to keep the distance from the lowest frequency in a diffuser to our seated position in order to maximize the diffusion of that wave form.

Now as a general rule we try to get as much diffusion, as many sequences, as many frequencies in our diffusers as we can. So we try to get the highest prime that we can. We want to make sure that we have those distances to work with.

Different Sound Diffuser Placement For Different Room Usage

If it’s a control room we’re probably going to want an absorptive front end and diffusion on the rear wall to prevent the slap back from the rear wall. For home theaters we want front and rear wall and maybe just ceiling. It depends on the number of channels. For critical listening, diffusion is good on the front and the rear walls because we’re trying to create a natural sound stage and environment.

So it just depends on the room and what you’re trying to use the room for in determining the placement of diffusion. But as a general rule try to get as much diffusion in the space that you have allowing for enough distance for the lowest frequency in the diffuser to fully form and , as I said above, we use the distance of the wavelength plus another fifty percent in our calculations. It seems to work really well. We don’t get any distortions or any anomalies at all.

In Summary

So I hope that helps you understand a little bit more about the positioning of diffusers for your particular room requirements. If you have a chance I would suggest you watch this sister video I made as part of understanding the diffusion process.

If you have any questions at any time I am always on hand to help answer them. Leave them in the comments section or email me at info@acousticfields.com. Also, if you would like a free analysis of your room, please complete the form on this page www.acousticfields.com/free-acoustic-treatment-room-analysis-tell-us-about-your-room/ and we will run a free analysis for you. If you would like to learn more about room acoustics please sign up for my free videos and ebook by joining the mailing list here. I send room tuning tips and things for you to test in your room every Wednesday. They are easy to follow and really help you enjoy more of your music.

Thanks and speak soon

Dennis Foley

I am an acoustic engineer with over 30 years’ experience in the business. My technology has been used in Electric Lady Land Studios, Sony Music of New York, Cello Music and Films founded by Mark Levinson, and Saltmines Studios in Mesa, Arizona, along with hundreds of others. Connect with me on Google+

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7 thoughts on “Sound Diffuser Placement – How To Position A Sound Diffuser

  1. Hello

    today I saw a studio having RPG in the front wall in middle of the speakers, isn’t a mistake?
    I always had the idea that should be absorbed in that area in order to get just clean sound from the speakers and noting else.

    I would love to hear some opinions

    • Hi Gigi,

      Their are no absolutes in acoustical treatment for the middle and high frequencies. Some prefer a diffused front end and some like absorption. It depends on the music and style of the engineer.


  2. Hello
    how will you place a sound diffuser in multi purpose auditorium.Like how can disperse around the hall with combination of refelectors and sound absorbents

  3. can you use the QD diffuser on front wall and or side wall with success. I have an older model and can stack it on top of a bass absorber in between the speakers. not sure i need it on the rear wall as its further from my listening position and it will have a plant shelf back there as well as bass traps in the corners so the plants will be in between the traps on rear wall spanning entire wall. So my question is I normally see QD diffuser on rear wall. want to make sure they are just as good on front wall before I place them or buy something else for this.

    • N, I am going to assume you are speaking about two channel listening. You do not state usage in your question. Diffusion on the front and rear walls will work well for that usage.

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