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

Doodski

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And what do you think is BEHIND those "diffusers" and the WHOLE front in the last (HT) picture? ;)
I honestly have no clue although I hope for the biggest baddestazz speakers known to mankind. :D I've seen some front ends and they can vary especially from the pic of the front end on that room.
 

poxymoron

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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.
This looks very helpful. I'll have a read of this tomorrow when I have less drink on me. Thank you.
 

bo_knows

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I honestly have no clue although I hope for the biggest baddestazz speakers known to mankind. :D I've seen some front ends and they can vary especially from the pic of the front end on that room.
Nope, it's BABA YAGA. ;):D

1670636584800.png
 

Doodski

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I have no idea what Baba Yaga is or whom. I do know that I made roll ups of twigs and branches after chopping down the back yard before moving. They burned awesome but smoked this dark green/gray vapor that made the neighbors complain or not...lol. We had about 35 backyard firepit hangouts the year before last. It was a hoot! :D
 

Bjorn

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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.
So what? They are selling products. It's well understood that attenuating early arriving specular reflections gives the highest insight to the recorded signal. A recording room is something else than a mixing or mastering room by the way.
 

Trdat

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I added 4 120 by 60 cm Bad panels in my very small room which is 4 m front to back and 6 m side to side and a standard apartement height. I use horn speakers with a 15 inch woofer.

Unfortunately, 3 of my bad panels are on one side of the room with the other one on the other side. I have pointed the speaker direction directly to the bad panels head on which are placed pretty much on the back sides and one on the back but enough distance to the MLP.


I can't say I hear a difference and I really don't know what I am looking for in measureemnts. I don't want to say I have better reverb times in the high frequency because that could just be higher volume for the high frequency through DSP without realising. But, there is a more even decay across the higher frequency in the decay graph in REW across all new measurements.

Any other measurement I am supposed to be looking at?
 

Bjorn

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Correct placement of treatment is key to hear differences and must be tailored to the directivity of the speaker. If that is done and the treatment is sufficiently broadband and effective, one should be able to hear a clear difference with doing enough AB testing.
Measurements can both be of the amplytude and time domain, but reverberation (RTx) are basically invalid in small rooms and no reason to look at these. Use impulse or an ETC instead and measure the speakers separately.

I generally don't recommend flat BADs to first reflection points in a room that is used for music. One is still able to hear discrete reflections with this product. The curved BAD Arc is much better where you can't hear comb filtering even at very close promiximites of the unit. However, with sufficient thickness for broadband effect (15 cm or 20 cm) they also cost a lot more. With 20 cm depth they work well down to 110 Hz area.
 

Trdat

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Correct placement of treatment is key to hear differences and must be tailored to the directivity of the speaker.
What is essentially the correct placement? For a small room is creating a timegap or breaking down specular reflections the goal? I thought perhaps creating some type of diffused reflections after a certain ms would give the impression of a larger room due to the reflections arriving after say 15ms, hence why I have the panels placed 5 metres away from the point source. Not that I calculated this, didn't really have any other option but seems like a good way to go about it.
If that is done and the treatment is sufficiently broadband and effective, one should be able to hear a clear difference with doing enough AB testing.
Measurements can both be of the amplytude and time domain, but reverberation (RTx) are basically invalid in small rooms and no reason to look at these. Use impulse or an ETC instead and measure the speakers separately.
I did notice on the ETC with seperate L/R measurements that there was much more diffused reflections.
I generally don't recommend flat BADs to first reflection points in a room that is used for music.
With a point source speaker aimed directly at the bad panel it is technically first reflection but its just less than 5 m away so not sure if that helps I could potentially point the speakers to the back wall which has a sofa and broadband absorbtion fully covered with rockwool even in the sofa. Would that be a better option? I just don't understand then how would any of the speakers polar pattern end up to the bad panel if the horn is 90 by 40 dispersion pattern?
One is still able to hear discrete reflections with this product. The curved BAD Arc is much better where you can't hear comb filtering even at very close promiximites of the unit. However, with sufficient thickness for broadband effect (15 cm or 20 cm) they also cost a lot more. With 20 cm depth they work well down to 110 Hz area.
They have 10cm thick broadband absorbtion behind them.
 

Bjorn

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What is essentially the correct placement? For a small room is creating a timegap or breaking down specular reflections the goal? I thought perhaps creating some type of diffused reflections after a certain ms would give the impression of a larger room due to the reflections arriving after say 15ms, hence why I have the panels placed 5 metres away from the point source. Not that I calculated this, didn't really have any other option but seems like a good way to go about it.

I did notice on the ETC with seperate L/R measurements that there was much more diffused reflections.

With a point source speaker aimed directly at the bad panel it is technically first reflection but its just less than 5 m away so not sure if that helps I could potentially point the speakers to the back wall which has a sofa and broadband absorbtion fully covered with rockwool even in the sofa. Would that be a better option? I just don't understand then how would any of the speakers polar pattern end up to the bad panel if the horn is 90 by 40 dispersion pattern?

They have 10cm thick broadband absorbtion behind them.
I can't go into all of this. It would end up with a discussion back and forth and which would require measurements, pictures, more explanation of placement, etc. This is where acoustic consultant come into play.

Absorption behind BADs doesn't anything with comb filtering and the lack of proper diffused energy, which is the drawback with this product. It's a product that works well for other applications. Depending on the material, it may not work well for the lows either.
 

Trdat

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I can't go into all of this. It would end up with a discussion back and forth and which would require measurements, pictures, more explanation of placement, etc. This is where acoustic consultant come into play.
I know, its complicated.
Absorption behind BADs doesn't anything with comb filtering and the lack of proper diffused energy, which is the drawback with this product.
Hence the Arc Bad panel.
 

Bjorn

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I see you're using Audiolense. You need to make sure you don't correct for certain room anomalies above the Schroeder if you want to get something out of acoustic treatment. Some type of correction with Audiolense can hinder you to hear improvements with certain acousic treatment.
 
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sarumbear

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So what? They are selling products.
So are you. How can that be part of a technical argument? I was referring to the company whose videos you post as reference but couldn't follow with any peer-reviewed ones.
 

Bjorn

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So are you. How can that be part of a technical argument? I was referring to the company whose videos you post as reference but couldn't follow with any peer-reviewed ones.
I'm selling both diffusers and absorbers. I make more money on diffusers, but I'm still not pushing them to the answer to everything. And I would never recommend treating so many surfaces as we see in these illustrations from Arithmetic in a mixing room or playback room. That can actually be detrimental. It's sellers talk and has nothing to do with optimal treatment.

Treatment of specular energy is well understood. Anyone with some decent understanding of the topic very well knows that treating early specular energy with scattering units that only work in a limited frequency area will greatly color the sound, and that broadband absorption of the same energy will get you much closer to the recording.

I've aleady told you that you need to contact them for a paper and further explanation. It's not on the open internet, which is the case with many studies.
 
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sarumbear

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I've aleady told you that you need to contact them for a paper and further explanation. It's not on the open internet, which is the case with many studies.
You are presenting an opposing argument to mine but so far you did not show any document, paper, test, etc. which agrees with you that most diffusers skew the FR in a room and should not be used. That's not how a technical argument works. Where is data, as they say...
 

Bjorn

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You are presenting an opposing argument to mine but so far you did not show any document, paper, test, etc. which agrees with you that most diffusers skew the FR in a room and should not be used. That's not how a technical argument works. Where is data, as they say...
The paper we're talking about here was regarding Skyline diffusers. Nothing else.

I have never said that that diffusers are necessarily skewing the frequency response of the room. That's your interpretation and shows that you don't understand what this is about.
Which is a bit strange coming from an acoustician, considering this a basic understanding of acoustics and acoustic products.
 
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sarumbear

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The paper we're talking about here was regarding Skyline diffusers. Nothing else.
Which is the subject!

I have never said that that diffusers are necessarily skewing the frequency response of the room. That's your interpretation and shows that you don't understand what this is about.
What about these?
Simply stating that diffusion is better is IMO quite misleading. Besides, much of what you are linking to are not proper diffusers but simple scattering units with a high level of lobing, focusing certain frequencies in certain directions, and very bandlimited that with alter the frequency spectrum. If the goal is accuracy (which it doesn't have to be of course), this type of treatment would be what one should avoid.
As previously mentioned, a Skyline diffuses very little and is very absorptive.

Which is a bit strange coming from an acoustician, considering this a basic understanding of acoustics and acoustic products.
I appreciate if you stop hiding behind semantics and show us the data to substantiate what you said. So far you showed no data, just words. There is no point in debating without data.

It's a paper from Arithmetic. You can see the same information in the video under " DIFFUSE Signature Discussion":
What next, referencing "YouTube" videos as reference? :eek:
 

Trdat

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Afaik , landlord of a hut chez Mussorgsky
Something like that:
I have no idea what Baba Yaga is or whom. I do know that I made roll ups of twigs and branches after chopping down the back yard before moving. They burned awesome but smoked this dark green/gray vapor that made the neighbors complain or not...lol. We had about 35 backyard firepit hangouts the year before last. It was a hoot! :D

It was a computer game that my little sister got as a present 20 years ago in Australia, it was called Baba Yaga and the Magic Geese, it was obvious that it was some type of Slavic or Russian folktale. I think it is but not 100% sure...
 

kthulhutu

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I see you're using Audiolense. You need to make sure you don't correct for certain room anomalies above the Schroeder if you want to get something out of acoustic treatment. Some type of correction with Audiolense can hinder you to hear improvements with certain acousic treatment.
Can you elaborate on what you mean, please?
 
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