Sound Diffusers 101: Free DIY Diffuser Designs

Sound diffuser scattering simulation. Diffusers reduce echoes and reflections by scattering sound waves in many directions.

Sound diffusers (or diffusors) are an acoustic treatment that many people overlook. Why? Diffusers are mysterious, misunderstood and not everyone can justify their cost.

Luckily, if you don’t wish to purchase diffusers there is an alternative: you can build them! Enter, the DIY sound diffuser. While there are many different DIY diffusers, I believe these optimized “stepped diffusers” are the easiest to build. If you can use a hammer, you can make them… and if you know a thing or two about woodworking, feel free to make the more sophisticated designs I’ve provided.

Click here to download the free blueprints, or keep reading to learn more. If you want to see how I designed these (using optimization), check out the free diffuser design thesis.

DIY Sound Diffusers (built by WhiteConstructionDesign.com)

Sound diffusers arranged for peak performance (see the free DIY plans). Built by John White at WhiteConstructionDesign.com.

 

Download the DIY Diffuser Blueprints

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Creative Commons License

Stepped Diffuser Designs in Chapters 7.3 and 8 of “The Lean Optimization of Acoustic Diffusers” by Tim Perry are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Consult RPG Diffusor Systems Inc. for additional restrictions on fractal diffusers. Background research draws from the works of Trevor Cox, University of Salford; Peter D’Antonio, RPG Diffusor Systems Inc.

   
 

Acoustic Diffusers 101

Here’s everything you need to start building diffusers. I’ll be updating this page periodically, so check back often!



Acoustic Diffusers and Near Field Scattering Simulations

Acoustic diffuser designs. Modular, optimized stepped diffuser (top). Fractal diffuser (bottom). Scattering simulations (right).


 
 

What’s a Sound Diffuser?

A sound diffuser is an acoustic panel used to treat echoes and reflections. Unlike absorption, diffusers preserve the liveliness of your room because they don’t absorb much sound energy. Instead, they disperse it, spreading the energy around the room.

An ideal acoustic diffuser is a surface that causes an incident sound wave from any direction to be evenly scattered in all directions.

 
 

Optimized Stepped Diffusers and Fractal Diffusers

Sound Diffuser Module A1-LF Sectional View Fractal Sound Diffuser Panel Acoustic Diffusers

To design the diffusers, I used a system that combines evolutionary optimization (simulated natural selection) with physical modeling. If you’re interested in the nerdy details, check out Chapters 6-7 of the diffuser design thesis.

The thesis gave birth to many possibilities for modular sound diffusers (large diffusers, assembled using small diffuser panels called modules). Here are the most promising designs:

  1. The Leanfuser™ (called A1-LF in the thesis) &#8212 a ridiculously simple, low profile modular stepped diffuser. (See the thesis for an extended design called A1-Frac, or the Leanfractal™)
  2. The Stepfractal™ (called B2-Frac in the thesis), which offers better diffusion but is less DIY friendly. This was designed by optimizing diffuser modules in an aperiodic array (explained in Chapter 7 of the thesis). Next, the optimized module’s shape was used to generate fractal geometries. Fractals are an elegant way to extend the bandwidth of the diffuser (improving its ability to scatter sound at higher frequencies).

The RPG Diffractal® (a nested broadband QRD diffuser) inspired me to optimize simple diffuser panels that can be easily fractalized. To protect the open source status of these stepped diffuser designs, I’ve licensed them under Creative Commons. These sound diffusers are free for you to build and use, but please don’t manufacture them with the intent of selling them.


DIY Diffusers

DIY sound diffusers. Modular, optimized stepped diffuser (left). Modular fractal diffuser (right).


 
 

DIY Sound Diffusers: Free Blueprints

These DIY diffusers have been optimized to balance performance with simplicity, so you can easily build them using basic tools.

DIY Diffuser Module A1-LF Sectional View Acoustic Diffuser Panel (Full Height) A1-LF Perspective Fractal Sound Diffuser Panel (Front)

Here are the free blueprints:

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DIY Diffuser Module A1-LF Fab Drawing

Diffuser Module Fabrication Drawing (5 modules side-by-side make a full diffuser).

DIY Diffuser Module A1-LF Fab Drawing (full height module)

DIY Diffuser Module Assembly (showing fabrication cuts for a full height module).


DIY Diffuser Module A1-LF Fabrication Cuts

Optimized stepped diffuser module (showing fabrication cuts).


 
 

Coming Soon: More Videos of Diffusion in Action!

 
 

The Acoustic Diffuser Build Gallery (Click Here to Visit)

Studio and venue owners, home recording hobbyists, HiFi enthusiasts, audiophiles and many others all over the world have built these diffusers. Here are photos of some example builds.

 
Fractal Sound Diffusers: 5 Leanfractal Panels. Built by Pablo Crespo.

Fractal sound diffusers DIY build: 5 Leanfractal (A1-Frac) diffuser panels assembled using Profiled Modulation 1. Built by Pablo Crespo.

 
Fractal Sound Diffuser

Fractal sound diffuser. Created by fractalizing an optimized stepped diffuser.

 
Fractal Sound Diffuser FDTD Simulation

Near field scattering simulation for fractal acoustic diffuser B2-Frac.

 
 

Diffusion Coefficients: How Well do the Diffusers Perform?

The autocorrelation diffusion coefficient is used to measure diffuser performance. In the images below (produced using AFMG Reflex Software), the diffusion coefficient has been averaged in one-third octave bands and plotted as a function of frequency.

High values of the diffusion coefficient indicate that a surface scatters sound uniformly to all receivers; low values tell us that a surface is concentrating reflected energy in one direction. The higher the coefficient at a particular frequency, the more effectively sound is diffused at that frequency.

RPG Diffusor Systems® is currently developing more advanced acoustical coefficient standards.

Detailed performance reports for these diffusers — and other optimized diffusers — are available here.

Get the Detailed Performance Reports

(Free Instant Download)


Stepped Diffuser A1-LF (The Leanfuser™) Performance Coefficients

BEM Simulation of Diffuser Module A1-LF

Boundary element model (BEM) simulation of stepped diffuser A1-LF (single module).


A1-LF Module Diffusion Coefficients, 0 Deg A1-LF Module Diffusion Coefficients, 45 Deg A1-LF Module Diffusion Coefficients, Diffuse Field


BEM Simulation of Diffuser Array A1-LF

Boundary element model (BEM) simulation of stepped diffuser A1-LF (array of five modules).


A1-LF Diffusion Coefficients, 0 Deg A1-LF Diffusion Coefficients, 45 Deg A1-LF Diffusion Coefficients, Diffuse Field


Applying Profiled Modulations to The Leanfuser™


Because the Leanfuser™ module is symmetrical, 5 modules placed side-by-side form a periodic array. A great way to increase the diffusion performance is to reduce this periodicity by mounting the modules at different depths. You can call this a profiled modulation. The image below shows an example, where 5 Leanfuser™ panels have been mounted at specific depths (see the blueprints to learn how to apply this modulation).

Diffusion Coefficients, Modulated Array of 5 A1-LF Panels

Diffusion coefficients for stepped diffuser A1-LF with a profiled modulation (array of 5 modules mounted at specific heights).



You can also mount 7 modules using a profiled modulation based on fractal self-symmetry. The image below shows an example of this, where 7 modules of the Leanfuser™ are mounted at different depths to create a shallow profiled modulation. Because the profiled modulation is derived from the depth sequence of the Leanfuser™, you can call this a fractal modulation. And if you applied this modulation to the fractal diffuser A1-frac, you’d have a 3rd order nested fractal!


Diffuser A1-LF, 7 Panels Arranged with a Fractal Modulation (BEM Simulation)

Stepped diffuser A1-LF with a profiled modulation based on fractal self-symmetry (array of 7 modules mounted at specific heights). Data obtained from a boundary element model (BEM) simulation.


A1-LF 7-Panel Fractal Modulation, Diffusion Coefficients, 0 Deg A1-LF 7-Panel Fractal Modulation, Diffusion Coefficients, 45 Deg A1-LF 7-Module Fractal Modulation, Diffusion Coefficients, Diffuse Field

If you did not mind a thick diffuser, you could take the fractal self-symmetry concept even further. For example, you could create a low frequency fractal stage with the proportions equal to the stepped diffuser proportions (I.e., keeping the width:depth ratio consistent). For the Leanfuser™, the width:depth ratio = 42 cm / 5 cm = 8.4. Considering an array of 7 acoustic diffuser panels (294 cm wide), the deepest step of the profiled modulation would be 294 cm / 8.4 = 35 cm. Since the deepest step of this stepped diffuser is 5 cm, you would scale all the depths by 35 cm / 5 cm = 7.

This would give you a profiled modulation of 7x[stepped diffuser depths]. The resulting diffuser would have an operational depth of 40 cm, which is a much deeper design than the one we started with!

Want to See How to Build these Sound Diffusers?

 Leanfractal diffuser shown beside a cross section of the Leanfuser Click Here to Download the Free Blueprints ›


 
 

Fractal Diffuser B2-Frac (The Stepfractal™) Performance Coefficients

BEM Simulation of Diffuser Module B2-Frac

Boundary element model (BEM) simulation of fractal diffuser B2-Frac (single module).


B2-Frac Module Diffusion Coefficients, 0 Deg B2-Frac Module Diffusion Coefficients, 45 Deg B2-Frac Module Diffusion Coefficients, Diffuse Field


BEM Simulation of Diffuser Array B2-Frac

Boundary element model (BEM) simulation for fractal diffuser B2-Frac (array of 5 modules).


B2-Frac Diffusion Coefficients, 0 Deg B2-Frac Diffusion Coefficients, 45 Deg B2-Frac Diffusion Coefficients, Diffuse Field      
 

More Sound Diffuser and Acoustic Treatment Resources

Check out the thesis to learn more about these diffusers and see how they were designed. Or, learn more about the practical applications of acoustic diffusers in the recording studio design papers.

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(Free Instant Download)

Many of you have told me you’d rather not build diffusers yourself and you simply want to buy them. Thanks for the interest, but right you can’t buy any diffusers I’ve designed! If you want them, you have to build them (or hire a carpenter to build them for you).

But if you really don’t want to build sound diffusers, and instead you want to buy them through me, check out the diffusers section of our acoustic treatment store. There you can learn about some of the acoustic treatments on the market by RPG Diffusor Systems and Vicoustic. You won’t find any cheap, ugly plastic diffusers there, but you will find some slick acoustic diffusers made from wood and bamboo.

Still looking to do your own build? Great! Download the free blueprints and I’ll send you all the information you need to get started. For answers to the most common DIY diffuser build questions, check out the FAQ and take a look at the build gallery.

 
 

Over to You

Now go ahead and build them, and please leave a comment below if you have any questions or insights! Also, I’m wondering

  • What’s the most likely material you’d use for building them?
  • What tools are available to you? Do you have access to woodworking equipment? CNC?


    • Depending where you live, I think bamboo lumber would be great construction material for DIY diffusers (and other acoustic panels). It’s a greener and cheaper alternative to hardwood, with a unique, exotic look. If bamboo does not grow near you, why not build these out of reclaimed lumber?

    Perk: If you build any of my DIY diffuser designs with reclaimed wood, bamboo lumber or another eco-friendly material, please let me know! If they look good I’ll post photos of your diffusers, and (with your permission) I’ll link to your website.

     

    by Tim Perry