While everyone has an idea of what having a room with “good sound” means, many people have never put thought into what it takes to create that “good sound.” 

It isn’t just the quality of the music or the sound mixing in a movie. “Good sound” often comes just as much from the listening environment.

Creating a sound environment with a sound diffuser

Making a great listening environment isn’t necessarily a matter of soundproofing a room. Often what you need is a well-placed sound diffuser.

Diffusing sound can be harder for a layperson to wrap their head around than sound absorption, but it is essential to creating a sonic experience that is rich and full instead of flat and sterile.

Effectively using sound diffusers requires understanding not just what they are, but where to place them in a room to get the best results—no matter if you are listening for business or fun.

What is a sound diffuser?

To understand what a sound diffuser does, you need to first understand a few principles of the physics of sound. You don’t need a Ph.D. or anything, but some knowledge of the basics will give context.

In some ways, sound operates kind of like light. When you shine a light at a mirror, the light reflects back at you. Sound does the same thing, except every hard, flat surface can serve as a mirror for it. That’s why your voice echoes more in some rooms than others. 

Another element of sound is that it comes in waves. A sound’s wavelength varies depending on its pitch. High pitched sounds have shorter wavelengths than deep, bass sounds. When you hear an echo, that’s a sound wave bouncing off a surface and coming back to you. 

So how do acoustic diffusers work? 

Unlike sound absorption panels that are made of soft materials with lots of air pockets that prevent sound waves from bouncing back at you, a sound diffuser allows for the sound to reflect—but it breaks up the reflection so you don’t get a clear echo. 

One of the benefits of using properly placed diffusers is that, because they don’t eliminate the sound waves that come at them, they don’t deaden the sound in an environment. Instead, they give a listening area a more full, complete sound. 

Different types of sound diffusers 

The purpose of your listening environment will affect the types of sound diffusers you choose. Diffraction in acoustics involves a lot of nuances. Do you need a 1D or 2D diffuser? Is a skyline diffuser right for you? What does any of that mean?

1D and 2D diffusers are acoustic diffusion panels whose names describe the planes on which sound is diffused. 1D diffusers look like half-cylinders and diffuse sound waves left to right if they are set up vertically and up and down if they are installed horizontally. 2D diffusers usually look like half spheres and diffuse sound left and right and up and down.

What are quadratic diffusers?

Quadratic diffusers are designed to diffuse sounds at many different frequencies. They will often use several vertical slats with diffusers calibrated for specific wavelength ranges. 

The benefit of this type of diffuser is that it provides even diffusion of sounds at a wide range of wavelengths whether those sound waves are on the high end or lower end.

How do skyline diffusers work?

Skyline diffusers operate similarly. They use wood columns of different lengths mounted on a wall for a similar purpose to a quadratic diffuser. A skyline diffuser is called that because it looks like a city skyline from the side. Before you ask “do wood sound diffusers work?” you can rest assured that they do.

But to build a good skyline diffuser, it’s important to be familiar with what’s known as a sound diffuser calculator or an acoustic diffuser calculator. These tools help calculate the lengths of wood required to address frequencies of sounds in the environment that you want to diffuse. Not every handyman will be familiar with these tools, so it’s wise to consult an expert.

But now that you know more about different types of sound diffusers, how do you know what kind you need and where to place them? 

Purposeful placement

To understand where to place a sound diffuser for maximum efficacy, you have to know what you want out of your listening experience.

Are you setting up a home theater? Are you listening to playback in order to mix music and create high-quality masters? Are you an audiophile that wants to hear your record collection in all of its vinyl glory? 

Your purpose in a room is one of the biggest factors in the placement of diffusers.

Another important factor is speaker placement and where in the room your “sweet spot” is located. Bringing in an expert for an acoustic treatment room analysis can help you figure out the best place to do your listening. 

Sound diffusion vs sound absorption

It is also important to remember that great sound diffusion isn’t a matter of sound diffusion vs absorption. Both are important for a pristine listening experience. Additionally, both are important to keep in mind when considering the people around you. You want the best possible listening experience but that doesn’t mean you want to force your whole house or workplace to listen to the same thing you are listening to through the walls. 

With all those caveats out of the way: where should you place sound diffusers?

Generally speaking, the best place to put sound diffusers are at the primary reflective points in your listening room. This is the place where the sound from your speakers will first hit a wall or surface to reflect back. When you don’t have diffusion or absorption, these points produce reverberation and echoes that muddy the listening experience.

With home theater diffuser placement, most of the sound will come from in front of you, so having diffusion along the rear wall is a must. With surround sound, having some 1D diffusers along the side walls to correspond with side speakers is also wise.

Diffusers in recording studios

Diffusion in recording studios is incredibly important. You want the best audio dynamic microphone definition. That means you don’t want a lot of echoing sounds getting picked up by your high-end mics and messing up your tracks. Again, you’ll want to utilize the back wall to control the sound that hits your microphone. A high-frequency diffuser along the back wall can do a lot of work to control the sound. Quadratic diffusers work great here, as do skyline diffusers which add a degree of aesthetic beauty to the room.

In sound mixing rooms, speaker set-up again plays a huge role in diffuser placement. Calculate where the primary reflective points are and place your diffusers there. Again, the back wall will be the primary diffuser location since that’s where the main speakers are generally facing. 

The limits of diffusers

Understanding how best to use sound diffusers also means recognizing their limits. Deep bass sound waves are difficult to deal with if diffusers are the only thing you’re working with. Bass tones have very long wavelengths which make them travel outside of small areas easily. Have you ever noticed how easy it is to hear bass notes coming from a car with a loud audio set up—even when you’re several yards away? That’s because deep sound waves like those can have four foot long wavelengths! A lot of materials just aren’t able to deal with something like that!

So when you look into how to trap bass in a room, it’s important to realize that special materials and special placements will be necessary. Placing absorption materials in the corners of your listening room that work in conjunction with your diffuser and absorber set up will help ensure that you control both the high-end and low-end sound you want to hear.

Trust the experts

Recognizing that sound diffusers can improve the quality of sound that you experience is only the first step. There is a lot of physics and geometry involved in room acoustic basics and even experienced do-it-yourselfers may need help. 

Understanding how to best use a sound diffuser in a small room, when to use a combination of diffuser and absorber, how to manage skyline diffuser placement, and many other questions can be overwhelming. By consulting with an expert to find your listening sweet spot, calculate your sound diffuser needs, and help you place those diffusers in the exact right spots, you’ll save effort and time. Time can be better spent experiencing amazing, full sound in a perfect listening room.

FAQ

What are sound diffusers?

Sound diffusers prevent echo by redirecting sound waves that hit them in different directions instead of allowing them to reflect.

Types of sound diffusers?

There are simple diffusers like 1D and 2D diffusers that redirect sound waves that hit them along one axis (1D) or two axes (2D). There are also quadratic and skyline diffusers which are designed with different diffusers addressing different frequency sound waves.

Diffusers vs absorbers?

Absorbers are typically made of porous materials that “catch” sound waves and do not allow them to reflect while diffusers are made of more solid materials that redirect sound waves without allowing for clear echoes.

Where do you put a sound diffuser?

Sound diffusers are most effective when placed at the primary reflective point (the first spot sound would bounce off of) of a sound source such as a speaker.

Where do you put skyline diffusers?

Skyline diffusers are most effective on the rear walls of listening areas so that they can diffuse sounds from the most prominent sound sources.

How do you use a sound diffuser?

You place the sound diffuser over the primary reflective point of a sound source.

Do sound diffusers work in small rooms?

Yes. In fact, diffusers in small rooms can make those rooms sound larger than they are, but it takes careful planning and understanding of the physics and geometry of sound.

Where should you put a diffuser in a room?

Diffusers work best when placed at a sound source’s primary reflective point.

What is the most sound absorbing material?

Soft and porous materials absorb sound best. Foam or cloth or other pliable materials with plenty of room for air will stop sound from reflecting.