The No.1 Website for Pro Audio
 Search This Thread  Search This Forum  Search Reviews  Search Gear Database  Search Gear for sale  Search Gearslutz Go Advanced
Bxi diffusers
Old 4 weeks ago
  #1
Lives for gear
 
Temple of Light's Avatar
 

Bxi diffusers

I recently came upon these as a possible diffusion tool...

https://www.amazon.com/BXI-Sound-Dif...ustomerReviews

I would love to know how many if any of you have used these in your studios?
How did you use them and how well did they work?
Your impressions and applications would be quite interesting, I wonder if these could be utilized as part of a cloud or first reflection array...It is a usual application in a home theatre environments, my application is a
mixing/tracking room. Any other experiences of using these as fronts for insulation stacks/panels?
Lastly, do the advertised specs for operable frequency range affected seem reasonable {410hz to 24.571Khz}?
Thanks all,

Edit: I discovered something much more intriguing...this...

http://www.acousticsfirst.com/diffuser-arttrim.htm

Same questions apply, I've been hunting for something like this sh!t for years....

Thanks again...



YYMV

Light

Temple

Last edited by Temple of Light; 4 weeks ago at 03:46 AM..
Old 4 weeks ago
  #2
Lives for gear
 

Welll.... put it this way: They claim to be QRD, but QRD diffusion is based on prime numbers.... prime numbers are always ODD (by definition), but those things have an EVEN number of wells... So they are not QRD! It's impossible to have a true QRD with an even number of wells. It would still diffuse somewhat, but the power spectrum will not be flat, and the lobing would get really ugly if you tried to modulate an array of such diffusers...

In addition, in order to work properly, the dividers between the wells need to be as thin as possible: The dividers in those things are enormous!

Next up: they claim to work from "410Hz - 24571Hz". I mean SERIOUSLY??? Up to 24 kilohertz? Ummmm.... I think not.

And down to 410 Hz? In the real world, it is well depth that controls the low frequency cut off point, and it is related to wavelength: Since that entire device is only 2.8" thick, even if the back panel has no thickness at all and the entire 2.8 inches is all well depth, it's not going anywhere near to 410 Hz.

Sooooo..... Nope! I would not use those things, because they are not what they claim to be.

Quote:
I wonder if these could be utilized as part of a cloud or first reflection array
They could not be used in an array, because the have an even number of wells. Lobing would be very problematic if you tried.

Also, for a control room, it's not a good idea to have diffusion on first reflection points. That's great for a listening room: eg, home theater, audiophile, etc., but not for a control room, for psycho-acoustic reasons. Yes, you do occasionally see that in supposedly high-end studios with QRD's on the walls at the reflection points... but one has to wonder about the designer's understanding of how the human brain and ears work, and the basic principles of control rooms response...



- Stuart -
Old 4 weeks ago
  #3
Lives for gear
 
Jens Eklund's Avatar
Quote:
Originally Posted by Temple of Light View Post
Lastly, do the advertised specs for operable frequency range affected seem reasonable {410hz to 24.571Khz}?
Absolutly not.
Old 4 weeks ago
  #4
Gear Maniac
 

Quote:
Originally Posted by Soundman2020 View Post
Welll.... put it this way: They claim to be QRD, but QRD diffusion is based on prime numbers.... prime numbers are always ODD (by definition), but those things have an EVEN number of wells... So they are not QRD! It's impossible to have a true QRD with an even number of wells. It would still diffuse somewhat, but the power spectrum will not be flat, and the lobing would get really ugly if you tried to modulate an array of such diffusers...

In addition, in order to work properly, the dividers between the wells need to be as thin as possible: The dividers in those things are enormous!

Next up: they claim to work from "410Hz - 24571Hz". I mean SERIOUSLY??? Up to 24 kilohertz? Ummmm.... I think not.

And down to 410 Hz? In the real world, it is well depth that controls the low frequency cut off point, and it is related to wavelength: Since that entire device is only 2.8" thick, even if the back panel has no thickness at all and the entire 2.8 inches is all well depth, it's not going anywhere near to 410 Hz.

Sooooo..... Nope! I would not use those things, because they are not what they claim to be.

They could not be used in an array, because the have an even number of wells. Lobing would be very problematic if you tried.

Also, for a control room, it's not a good idea to have diffusion on first reflection points. That's great for a listening room: eg, home theater, audiophile, etc., but not for a control room, for psycho-acoustic reasons. Yes, you do occasionally see that in supposedly high-end studios with QRD's on the walls at the reflection points... but one has to wonder about the designer's understanding of how the human brain and ears work, and the basic principles of control rooms response...



- Stuart -
I really appreciate you and your energetic explanations, Stuart, but sometimes you are so into theory .... Do you have measurements on corrugated surfaces that show the superiority of a QRD above something random? And not measurements done by a salesman, but by yourself :-).
Old 4 weeks ago
  #5
Lives for gear
 

Old 4 weeks ago
  #6
Lives for gear
 
boggy's Avatar
Dear Stuart,

Quote:
Originally Posted by Soundman2020 View Post
Welll.... put it this way: They claim to be QRD, but QRD diffusion is based on prime numbers.... prime numbers are always ODD (by definition), but those things have an EVEN number of wells... So they are not QRD!
Yes, it is a 8x8 part of "something" of ninth order, while 9 is not prime.
Quote:
Originally Posted by Soundman2020 View Post
It's impossible to have a true QRD with an even number of wells. It would still diffuse somewhat, but the power spectrum will not be flat, and the lobing would get really ugly if you tried to modulate an array of such diffusers...
RPG Acoustical Systems LLC, doing the same for years. And virtually nobody really care about aliasing when people build multiple arrangements with the same (even order) modules. Founder of that company is Dr Peter D'Antonio, one of authors of a number published scientific papers about diffusers, and book "Acoustic Absorbers and Diffusers: Theory, Design and Application"

Look for their Omniffusor, and you will find that listed BXI product did not came from nowhere.

Quote:
Originally Posted by Soundman2020 View Post
In addition, in order to work properly, the dividers between the wells need to be as thin as possible: The dividers in those things are enormous!
Fins (dividers) can be avoided if it is more practical... but I agree that this "fins" are too wide. It is better to avoid them totally. An old AES paper exists where this is described.
Quote:
Originally Posted by Soundman2020 View Post
Next up: they claim to work from "410Hz - 24571Hz". I mean SERIOUSLY??? Up to 24 kilohertz? Ummmm.... I think not.

And down to 410 Hz? In the real world, it is well depth that controls the low frequency cut off point, and it is related to wavelength: Since that entire device is only 2.8" thick, even if the back panel has no thickness at all and the entire 2.8 inches is all well depth, it's not going anywhere near to 410 Hz.

Sooooo..... Nope! I would not use those things, because they are not what they claim to be.
Whatever they "claim" for "frequency response" (which is not true), even order (8x8) part of odd order (9x9) diffuser cannot be modulated or rotated to decrease aliasing for just a bit, because it is fully symmetrical. And most respected company in our area (RPG), doing the same for years... without hesitation, even if in book, noted above, everybody can find described a reasons WHY that way is bad for multiple diffuser modules arrays.
Yes, they can arrange them to the fractal type of array, but this is not much.
Quote:
Originally Posted by Soundman2020 View Post

They could not be used in an array, because the have an even number of wells. Lobing would be very problematic if you tried.
There are other ways to build arbitrarily long number of wells array for diffusing surface fully aperiodic and with slightly better diffusion coefficient than Schroeder type of similar order. With smaller number of different well heights... and, also, number of different well heights is not increased with diffuser length.

You can find more info about that here:

A Novel Approach of Multichannel and Stereo Control Room Acoustic Treatment, Second Edition, 140. AES Convention, Paris, 2016.

Quote:
Originally Posted by Soundman2020 View Post
Also, for a control room, it's not a good idea to have diffusion on first reflection points.
Why?

I designed about ten different Control Rooms with all walls and ceiling diffusion at first reflection points, and, now, I see no reason to avoid that design principle.

E.g. inside, with all diffusors on walls/ceiling, when listening, people usually notice that room virtually "disappear", or become less pronounced, also, it become, subjectively and acoustically, even "bigger". People with trained ears, can hear details in production, they never heard from recordings they know for many years. I see no reason NOT to have that type of room behavior in music production control room (recording, mixing and mastering), where people doing their jobs for living, not just for fun.

Quote:
Originally Posted by Soundman2020 View Post
That's great for a listening room: eg, home theater, audiophile, etc., but not for a control room, for psycho-acoustic reasons. Yes, you do occasionally see that in supposedly high-end studios with QRD's on the walls at the reflection points... but one has to wonder about the designer's understanding of how the human brain and ears work, and the basic principles of control rooms response...
Not good for Control Rooms because psycho-acoustic reasons?
Psycho-acoustics is a reason why diffusion at all boundaries in rooms (still not floor, yet ), works just great in Control Rooms, because our brains can recognize diffuse reflections then ignore them, and focus on direct sound from speaker. But, as you can imagine, without fully absorbing or avoiding room reflections, and making room difficult for comfortable work... Things in acoustics are not always obvious and logical, I believe you know that.

People needs reflections because they are used to live with them. Making reflections diffuse just facilitate music production work, and keep enough reflected energy in the room, to help people becoming less tired after couple of hours of work.

You can find more about our first attempt to do that, described here:

Acoustical Design of Control Room for Stereo and Multichannel Production and Reproduction—A Novel Approach, 129 AES Convention, San Francisco, 2010.

Cheers


Last edited by boggy; 4 weeks ago at 08:14 PM..
Old 4 weeks ago
  #7
Lives for gear
 
Yannick's Avatar
 

Quote:
Originally Posted by boggy View Post
Why?

I design about ten different Control Rooms with all walls and ceiling diffusion at first reflection points, and, now, I see no reason to avoid that design principle.
I have the same experience in my room, with diffusion on all the first reflection points in the horizontal plane. It just sounds bigger & more precise. Yes, I compared with thick absorption.

I asked one well-respected AE (who designs NE rooms, with some diffusion) about this, when he himself said it should not be done on first-reflection points. My question was: does your diffusor (which is mounted in another spot than a first reflection point of course) not become a diffused first reflection point even when it is shifted in space ? (I never got an answer)

I guess, even experienced acoustics engineers can paint themselves in a corner.
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Similar Threads
Thread
Thread Starter / Forum
Replies
Syphax / Studio Building / Acoustics
3
bokaasen / Studio Building / Acoustics
23
pompon / Studio Building / Acoustics
1
MyPutzyRod / Studio Building / Acoustics
1

Forum Jump
Forum Jump