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Wood acoustic diffusers have become a decorative item - loved the idea!

bo_knows

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3D art as diffusers. Your second post got me wondering how hard it would be to have the blocks actuated to dial in a specific response. Some day I suppose. Does anybody offer an absorbent panel with adjustable wood slats mounted in front (like vertical blinds) yet?
Yes.

 

bo_knows

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I really have to thank you @sarumbear for opening this thread! I have now discovered that GIK diffusors over my desk makes a dramatic improvement in sound quality in my office. It never really occurred to me to try and test them up there. I also tested the GIK diffusors on my front wall, but actually prefer the absorption that I currently have. The same goes for the large absorbtion panel behind the door in the image below. Next I was thinking how I wish it was easy to test them on the ceiling, and then I realized that I had a tool to hold them them quickly, easily, and secure enough for testing (see pic).

I had no idea how much the ceiling over my desk was interfering with my sound quality! I also tested an absorber up there and the diffusor is noticeably better. I get this nice airiness ambience over my head. The only disappointing part is that I promised these panels to my wife for her office, so now I need to order more. The second I took them down it was a bummer.

View attachment 242706
This is a "hybrid panel", meaning an absorber with a scattering plate. Not a true diffuser. They work and as stated here, you CAN sit closer to the panel. I do like the look of your room. Panels on the ceiling have an inch gap which will make those 4-inch perform as well as 5-inch panels. Good job.
 
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Bjorn

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This is a "hybrid panel", meaning an absorber with a scattering plate. Not a true diffuser. They work and as stated here, you CAN sit closer to the panel. I do like the look of your room. Panels on the ceiling have an inch gap which will make those 4-inch perform as well as 5-inch panels. Good job.
True. Diffusion is an even distrubution of the sound. What we get with scattering units is an uneven distribution of the sound, focusing more or less energy in certain directions. Just like the speaker's polar is important, the polar of the diffuser is also. We don't want polar lobing (frequency deviations), since this will color the sound.
Polar lobing.jpg


Thus it's crucial to have measurements of the products one is considering. A proper measurement should show both scattering, diffusion and absorption.
And always be measured with at least three units next to each other in order to see how they perform with multiples. The reason for the latter is that many diffusers will start to loose diffusion coeffiency due to periodicity. So how they perform alone might be very different from how they work put together.

Diffusjon vs spredning.jpg



Take note that typical 2D Skyline diffusers are higly absorptive and diffuse very little. These are basically outdated products compared to what's available today.
 
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sarumbear

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I wrote a short piece trying to explain diffusers. I hope it will be of use to the members. I am a retired acoustician with masters degrees on both acoustics and electronics.

How does sound diffusers work and how to use them​

“Good sound” isn’t just the quality of the music or the sound mixing of a track. “Good sound” most often is the quality of your listening room. Soundproofing a room will not create a good sound, nor damping the reflections will. Often what is missing is a well-placed acoustic diffuser.

During my long life I have experienced that the concept of sound diffusion is often harder for a layperson to understand than absorption. However, we must strive to create an experience that rich and full instead of flat and sterile. The enjoyment of music and the clarity of voice can only happen in a live room that has a wide and smooth reverberation. That can only be achieved with using diffusers along with absorbers.

What Is a diffuser?​

To understand what a diffuser does, you need to first understand a few principles of the physics of sound. Sound waves behave like light. When you shine a light at a light reflective surface, the light reflects at you. Sound waves act like light. However unlike light, every hard, flat surface can serve as a mirror for sound.

If we continue in the light analogy, an absorber is like a black wall, very little light is reflected from it. Whereas a diffuser is like a surface where small bits of broken glass of different colours scattered on it. They don’t block the light; they reflect them at so many angles that the reflected colour is white.

Sound absorption panels are made of soft materials with lots of air pockets. Those prevent sound waves from bouncing back at you. Whereas a sound diffuser allows for the sound to reflect—but it breaks up the reflection to many angles so that you do not hear a distinct echo. By not deadening the sound they create a pleasant sounding room.

Diffuser types​

Diffraction in acoustics involves a lot of nuances. What type of diffuser you need depends on your needs and the room. The industry has given names to various diffusers: 1D, Quadratic (QRD), Skyline, etc. What does any of that mean?

The so called 1D diffusers are panels whose names seems to be derived from the number of planes on which sound is diffused. They are half-cylinders and diffuse sound waves left to right if they are positioned vertically and up and down if they are positioned horizontally. They are not very effective. Your money and space is better utilised on a QRD or Skyline diffuser.

Quadratic (QRD) diffusers are designed to diffuse sounds at different frequencies. They will often use several vertical slots that are calibrated for a specific frequency range. This will allow diffusion of sounds at a wide range of frequencies in both ends of the spectrum.

Skyline diffusers works at multiple angles. It scatters sound both horizontally and vertically. They are the best choice if you have the space. They are called a skyline diffusers because from the side they look like a city skyline. They are formed with (often) wooden columns of different lengths glued together. To build a skyline diffuser, it’s important to use a special diffuser calculator to aid you in calculating the lengths of wood required.

Where should I place the diffusers?​

To understand where to place a sound diffuser for maximum efficacy, you must know what you want out of your listening experience. Are you setting up a home theatre? Are you mixing music and create high-quality masters? Are you an audiophile that wants to achieve the best sound possible in their room? Your purpose is the major factor to decide the placement of diffusers. Another factor is the speaker placement and where your “sweet spot” is located. However, for a good sounding room the decision is not the choice between sound diffusion and absorption. Both are important for a pristine listening experience.

You must place diffusers at the primary reflective points. That is where the sound from your speakers will first hit where the sound will reflect -- a wall or surface. When you have neither diffusion nor absorption, those reflections will produce reverberations and echoes, which will diminish the listening experience. In a home theatre most of the sound will come from the front, so having diffusion along the rear wall is a must. However, using 1D diffusers along the side walls to correspond with side speakers is also wise.

The limits of diffusers​

Low frequency sub-bass sound waves are difficult to deal with if diffusers are the only thing you’re working with. Bass frequencies have very long wavelengths and most materials just aren’t capable to deal with them. To manage bass in a room special absorbers must be used. They are often called bass-traps and should be placed in the corners of your listening room. They work in conjunction with your diffuser and absorber set. That way you can control both the high-end and low-end sound of the room.

Employ an expert*​

Recognising that sound diffusers may improve the quality of sound in your room is only the first step. There are lots of aspects involved in room acoustics and even experienced do-it-yourself'ers may need help. An expert will help you not only show you but will also help you to understanding how to best use a sound diffuser in your room, whether to use a diffuser/absorber combo, how to place skyline diffusers, etc.

*This is not an ad for my services. I’m retired. However, I’m happy to help ASR members within the limits of a forum communications.

Note: I’ve edited the diffuser types section to clarify what 1D diffusers are.
 
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Bjorn

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1D and 2D diffusers are acoustic diffusion panels whose names tell the number planes on which sound is diffused. 1D diffusers are half-cylinders and diffuse sound waves left to right if they are positioned vertically and up and down if they are positioned horizontally. 2D diffusers look like half spheres and diffuse sound left and right and up and down. Neither are very effective. Your money and space is better utilised on a QRD or Skyline diffuser.
What you're saying here doesn't make sense. A QRD is a 1D diffuser and Skyline is a 2D diffuser.

As previously mentioned, a Skyline diffuses very little and is very absorptive. We have much better products today.
The standard QRD has been improved considerably. For small rooms, diffusion above 4-5kHz is quite important.

RPG diff developm.jpg



A fact to be aware is that when using diffusion at early reflection points one ends up with somewhat bandlimited treatment. Since most diffusers don't diffuse much below 500 Hz and many not that low either. Most diffusers also requires the distance of 3 times the cut off frequency, or at least 2 times to work well. This means that absorption with high effect to the Schroeder frequency is in many cases the better option for certain surfaces. Or hybrid product that diffuses the highs and absorbs below.
 
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sarumbear

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What you're saying here doesn't make sense. A QRD is a 1D diffuser and Skyline is a 2D diffuser.
Read my description of the 1D and 2D diffusers please.
1D and 2D diffusers are acoustic diffusion panels whose names tell the number planes on which sound is diffused. 1D diffusers are half-cylinders and diffuse sound waves left to right if they are positioned vertically and up and down if they are positioned horizontally. 2D diffusers look like half spheres and diffuse sound left and right and up and down.

As previously mentioned, a Skyline diffuses very little and is very absorptive.
You repeat that but not show any data to substantiate it.

We have much better products today.
The standard QRD has been improved considerably. For small rooms, diffusion above 4-5kHz is quite important.
What I said for QRD diffusers that you disagree?

The enjoyment of music and the clarity of voice can only happen in a live room that has a wide and smooth reverberation. That can only be achieved with using diffusers along with absorbers.
A fact to be aware is that when using diffusion at early reflection points one ends up with somewhat bandlimited treatment. Since most diffusers don't diffuse much below 500 Hz and many not that low either. Most diffusers also requires the distance of 3 times the cut off frequency, or at least 2 times to work well. This means that absorption with high effect to the Schroeder frequency is in many cases the better option for certain surfaces. Or hybrid product that diffuses the highs and absorbs below.
You are basically agreeing with what I said at the very beginning. I fail to understand your objection.
 
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Bjorn

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1.Read my description of the 1D and 2D diffusers please.



2. You repeat that but not show any data to substantiate it.


3. What I said for QRD diffusers that you disagree?



4.You are basically agreeing with what I said at the very beginning. I fail to understand your objection.
1. I did. However, you also said that: "Neither are very effective. Your money and space is better utilised on a QRD or Skyline diffuser".
And this doesn't make any sense since these are 2D and 1D diffusers.

2. There have been some papers or measurements showing that Skyline diffuses little. I can't find it at the moment, other than the measurement below which shows a clear loss of energy at certain frequencies:
Skyline.jpg


However, I don't think this shows the whole picture. A problem is that we may not have accurate measurement standards today for diffusion. We have done a lot of AB comparisons between units, and it's very evident that the Skyline remains very little energy compared to a product like the Diffractal. Even the BAD Arc product, which is a hybrid product with only some 2D diffusion above 800 Hz, clearly sounds more "lively" than the Skyline.

3. My comment was a general comment and related to the above.

4. While I think it's great to focus on diffusers, I don't agree with much of what you've written in the opening here. The better or correct type of treatment very much depends. Stating generally that absorption often creates more issues than it solves and diffusion is a better approach is IMO very misleading information. And then you link to products with no proper data and obviously most are band limited simple scattering units. That type of treatment will creates it's own issues for sure.
 
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sarumbear

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1. I did. However, you also said that: "Neither are very effective. Your money and space is better utilised on a QRD or Skyline diffuser".
And this doesn't make any sense since these are 2D and 1D diffusers.
I was using the marketing words used by most sellers. Not to mean one or two dimensional.

2. There have been some papers or measurements showing that Skyline diffuses little. I can't find it at the moment, other than the measurement below which shows a clear loss of energy at certain frequencies:
View attachment 248809
May I see that product's page, please? The reason I'm asking is RPG shows a different chart and showers praise for their Skyline diffuser and seems to agree with what I say.

RPG utilised advanced primitive root number theory to design the most powerful and aesthetic two dimensional omnidirectional diffusing surface in the acoustical industry. Interfering reflections can be controlled by absorption or diffusion. In small rooms, it is often desirable to control interfering reflections and provide an ambient sound field using diffusion instead of absorption. When the room’s surfaces are relatively close to the listener, a very efficient diffusing surface is needed. To solve this problem, RPG patented the Skyline®. It is the industry’s first — and most efficient — omnidirectional primitive root number theory two dimensional diffusor. The Skyline scatters incident sound uniformly so that the acoustic glare in all directions is minimized.
skyac2.gif


4. While I think it's great to focus on diffusers, I don't agree with much of what you've written in the opening here. The better or correct type of treatment very much depends. Stating generally that absorption often creates more issues than it solves and diffusion is a better approach is IMO very misleading information.
We have to agree to disagree then. However, it is nice to see that at least one manufacturer agrees with me as they say in the highlighted text above.
 

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I was using the marketing words used by most sellers. Not to mean one or two dimensional.


May I see that product's page, please? The reason I'm asking is RPG shows a different chart and showers praise for their Skyline diffuser and seems to agree with what I say.


View attachment 248811


We have to agree to disagree then. However, it is nice to see that at least one manufacturer agrees with me as they say in the highlighted text above.
It's a paper from Arithmetic. You can see the same information in the video under " DIFFUSE Signature Discussion":

The absorption data from RPG above shows higher absorption around 315 Hz than what's usual for diffusers, but that shouldn't be the main reason either since it's low in frequency.
What I can tell you though is that subjectively the difference between Skyline and certain other diffusers is huge in the experience of absorption or "remaining of energy".

It's fine to disagree. I personally use fairly little absorption above Schroeder myself in my two-channel listening room and more diffusion, but that's because of the room dimension where I have very good distance to several surfaces besides a narrow speaker directivity (large horn speakers).
 
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sarumbear

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It's a paper from Arithmetic. You can see the same information in the video under " DIFFUSE Signature Discussion":
I rather read the paper. I appreciate if you are able to post a link. It’s nice to see a acoustical products supplier concentrates on diffusion:

At Arithmetic Design, we are dedicated to ensuring our clients have updated information on the DIFFUSE System.

And, points to the benefit of diffusers in almost all key positions they list.


I like it when suppliers agree with me :)

PS. They may have gained a customer in me. I have a place for their glass diffuser.
 
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bo_knows

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What you're saying here doesn't make sense. A QRD is a 1D diffuser and Skyline is a 2D diffuser.

As previously mentioned, a Skyline diffuses very little and is very absorptive. We have much better products today.
The standard QRD has been improved considerably. For small rooms, diffusion above 4-5kHz is quite important.

View attachment 248788


A fact to be aware is that when using diffusion at early reflection points one ends up with somewhat bandlimited treatment. Since most diffusers don't diffuse much below 500 Hz and many not that low either. Most diffusers also requires the distance of 3 times the cut off frequency, or at least 2 times to work well. This means that absorption with high effect to the Schroeder frequency is in many cases the better option for certain surfaces. Or hybrid product that diffuses the highs and absorbs below.
Hello Bjorn,

Thank you for letting me (us) know that there was an actual improvement to the diffractal qrd diffuser.
I didn't know about the other two modifications to the design (modffusor and modffractal). I don't have credentials or want to oppose/argue with anyone on this forum but diffusion was not the best option in my small room. I played with qrd and hybrid panels (scattering effect) for the first reflection point and it was just too bright for my ears. I end up using the absorption panels to create the RFZ. To keeps some liveliness in the room, I used scatter plates for the rest of the panels. I know this comes down to preference but I like precise imaging and good soundstage which is achieved.
Also, I don't sit or have a setup like a regular mixing position where the listener sits in 1/3 of the space from the front wall so QED diffusers can be used in the back wall since there will be an adequate length for them to work properly. My head is 4-5 feet away from the back wall, and I didn't feel that it was enough space for a 9-inch deep QRD. Anyway, I'll stop rambling, just sharing my experience.
P.S. If anyone who lives in the Dallas area is interested in purchasing some of my DIY QRD, send me a PM. :)
 

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Bjorn

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I rather read the paper. I appreciate if you are able to post a link. It’s nice to see a acoustical products supplier concentrates on diffusion:
You need to contact Arithmetic about the paper and more information.
 

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Hello Bjorn,

Thank you for letting me (us) know that there was an actual improvement to the diffractal qrd diffuser.
I didn't know about the other two modifications to the design (modffusor and modffractal). I don't have credentials or want to oppose/argue with anyone on this forum but diffusion was not the best option in my small room. I played with qrd and hybrid panels (scattering effect) for the first reflection point and it was just too bright for my ears. I end up using the absorption panels to create the RFZ. To keeps some liveliness in the room, I used scatter plates for the rest of the panels. I know this comes down to preference but I like precise imaging and good soundstage which is achieved.
Also, I don't sit or have a setup like a regular mixing position where the listener sits in 1/3 of the space from the front wall so QED diffusers can be used in the back wall since there will be an adequate length for them to work properly. My head is 4-5 feet away from the back wall, and I didn't feel that it was enough space for a 9-inch deep QRD. Anyway, I'll stop rambling, just sharing my experience.
P.S. If anyone who lives in the Dallas area is interested in purchasing some of my DIY QRD, send me a PM. :)
Your experience isn't surprising to me. Supressing early arriving reflections gives better imaging and is a more correct way of treating a room. Attenuating early specular energy gives the highest insight to the recorded signal. Diffusion of this type of energy will color the recording.

With only 4-5 feet to the rear wall, absorption and in especially in the center where the distance is the shortest is generally better IMO. You might find BAD Arcs on the sides of the rear wall to work well, but that something you would have to test. Take note that it should be the thick BAD Arcs (6" or 8") and not the flat BADs.
 

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Your experience isn't surprising to me. Supressing early arriving reflections gives better imaging and is a more correct way of treating a room. Attenuating early specular energy gives the highest insight to the recorded signal. Diffusion of this type of energy will color the recording.

With only 4-5 feet to the rear wall, absorption and in especially in the center where the distance is the shortest is generally better IMO. You might find BAD Arcs on the sides of the rear wall to work well, but that something you would have to test. Take note that it should be the thick BAD Arcs (6" or 8") and not the flat BADs.
This is a sample of recorded music in a small room that has diffusers used throughout the space.
I've listened to the sample with my headphones (HD 660s) and I notice that music that was recorded in his space sounds like there are more harmonics, dynamics, decay, "reverb" (I'm not sure how to express myself but to use those words) or brighter sounds in direct comparison to the recording.
I was not there but this is what I heard over the youtube video. This type of sound may be preferred by some but I would say it's a departure from the recording. John (the gentleman in the video) has put a tremendous amount of work into creating those treatments and I don't want to downplay his efforts. This is just my observation.

 
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There's a good reason why diffusion is rearely used to treat early arriving specular energy in studios. It's a step away from accuracy, even with the best diffusers.
 
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There's a good reason why diffusion is rearely used to treat early arriving specular energy in studios. It's a step away from accuracy, even with the best diffusers.
Is that why the company you referred earlier suggest using them on most surfaces in a studio? :facepalm:

Recording Studio​

Each element of the DIFFUSE System has been applied in the most demanding professional studios. DIFFUSE products can be mixed and matched as the emphasis of the facility demands. The modularity of the system allows engineers to tune the space with accuracy never before seen in a single product line.
 

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Is that why the company you referred earlier suggest using them on most surfaces in a studio? :facepalm:

Recording Studio​

Each element of the DIFFUSE System has been applied in the most demanding professional studios. DIFFUSE products can be mixed and matched as the emphasis of the facility demands. The modularity of the system allows engineers to tune the space with accuracy never before seen in a single product line.
I am doing a viewing experiment. From the first to the last image of the sound treatment in this webpage. I never read a word. I am just looking and from what I see a huge auditorium etc can really rely on sound technology. I see the difference. :D
z 1.png

z 2.png

z 3.png
 

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I have a 7.1.4 HT room and I thought the overhead Atmos effects were quite subdued, even with channel lift from the AVR. Like I heard the speakers but it didn't congeal into an effect.

So I bought this kind of diffuser from GiK:

pattern-2d-a.jpg


I installed all of them in the ceiling (they're 59×59cm so I simply replaced four tiles).

It did the trick. Now the ceiling feels quite lively and Atmos rain like actual rain. Or perhaps it's just my imagination. In any case, they look awesome, better than in the picture.
 

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I have a 7.1.4 HT room and I thought the overhead Atmos effects were quite subdued, even with channel lift from the AVR. Like I heard the speakers but it didn't congeal into an effect.

So I bought this kind of diffuser from GiK:

View attachment 248885

I installed all of them in the ceiling (they're 59×59cm so I simply replaced four tiles).

It did the trick. Now the ceiling feels quite lively and Atmos rain like actual rain. Or perhaps it's just my imagination. In any case, they look awesome, better than in the picture.
1950’s IBM called, they want their punch cards back…
 

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