A friend of mine has been asking me about building him either some quadratic or skyline diffusers. He lined every wall in his listening space with acoustic panels and he's now decided he doesn't like how dull it sounds.
I purchased a book detailing the BBC designs of diffusers and figured that would be a good place to start. He's asking about making some pretty large panels to hang from his 10' ceilings, 4x8' size panels.
My question for anyone whom might know is. Are the size of these types of diffusers scalable?
For example if a quadratic diffuser calls for a 4x4" square well, can that be expanded to a 6x6" square well?
Or in the case of a skyline style diffuser where plans call for 2x2" blocks at different heights. Can that be scaled to say a 4x4" block and still use the same heights outlined in the plans for 2x2" blocks?
Most of these designs make a roughly 2x2' panel, if I were to expand this to 4x4' instead of essentially making 4, 2x2' panels can these designs be scaled to accommodate a larger size panel?
I purchased a book detailing the BBC designs of diffusers and figured that would be a good place to start. He's asking about making some pretty large panels to hang from his 10' ceilings, 4x8' size panels.
My question for anyone whom might know is. Are the size of these types of diffusers scalable?
For example if a quadratic diffuser calls for a 4x4" square well, can that be expanded to a 6x6" square well?
Or in the case of a skyline style diffuser where plans call for 2x2" blocks at different heights. Can that be scaled to say a 4x4" block and still use the same heights outlined in the plans for 2x2" blocks?
Most of these designs make a roughly 2x2' panel, if I were to expand this to 4x4' instead of essentially making 4, 2x2' panels can these designs be scaled to accommodate a larger size panel?
Hi,
Short answer: no they are not scalable ( the dimension are related to bandwidth where they are efficient).
Given the size i would use a design like the one from member B.Waslo here ( homedepot diffusor thread here)
Or some design from Arqen :
http://arqen.com/
Skyline and schroeder are different: Skyline are 3d while schroeder 2d ( the scattering response). Despite lacking 1 'D' Schroeder based are more effective than skyline.
Remember for them to be useful you'll need to be distant 3x the lower wavelength the diffusor will act upon.
Short answer: no they are not scalable ( the dimension are related to bandwidth where they are efficient).
Given the size i would use a design like the one from member B.Waslo here ( homedepot diffusor thread here)
Or some design from Arqen :
http://arqen.com/
Skyline and schroeder are different: Skyline are 3d while schroeder 2d ( the scattering response). Despite lacking 1 'D' Schroeder based are more effective than skyline.
Remember for them to be useful you'll need to be distant 3x the lower wavelength the diffusor will act upon.
Thanks a ton for the info!
I had totally forgotten about Arqen designs, those and the Home Depot diffusers would definitely be easier to build on a large scale like he's interested in doing.
For my buddies listening space he wants something aesthetically pleasing and I think any of these designs would definitely work. And would definitely be much easier for me to build as well. I wasn't looking forward to making two 4x8' skyline panels, and he probably wouldn't want to see the labor bill for doing so. Hopefully I can sell him on one of these simpler to construct designs.
I had totally forgotten about Arqen designs, those and the Home Depot diffusers would definitely be easier to build on a large scale like he's interested in doing.
For my buddies listening space he wants something aesthetically pleasing and I think any of these designs would definitely work. And would definitely be much easier for me to build as well. I wasn't looking forward to making two 4x8' skyline panels, and he probably wouldn't want to see the labor bill for doing so. Hopefully I can sell him on one of these simpler to construct designs.
Hi,
What kind of panel did your friend used? ( reference if commercial product, if diy materials used).*
What is the size of the room?*
Another option as there is already some absorber panels on walls could be to clone the approach of a BAD panel ( RPG's product).
If you can have access to a laser or water cuting machine ( or other way) to cut a metal sheet (1 to 2mm height from stainless steel to aluminium) it is possible ( most infos are availlable through the patent). It is iinteresting because of it's low depth and effectivity past 1khz as diffusor ( below 1khz it act as an absorber).
A rule of thumb for balanced sounding room is 1/3 absorbsion, 1/3 reflection, 1/3 diffusion ( in m2/ft2).
*absorber used is needed to have an idea of the freq range which have been overtreated. It will at turn decide of the bandwith ( the depth) needed for the diffusors.
The size of room ( and if possible layout) will help define the 'overall' lower freq reasonably possible hence the maximum depth of diffusors ( you need 3x time the lowest wavelength distance for the diffusor to be effective, bla, bla, bla,...
) .
What kind of panel did your friend used? ( reference if commercial product, if diy materials used).*
What is the size of the room?*
Another option as there is already some absorber panels on walls could be to clone the approach of a BAD panel ( RPG's product).
If you can have access to a laser or water cuting machine ( or other way) to cut a metal sheet (1 to 2mm height from stainless steel to aluminium) it is possible ( most infos are availlable through the patent). It is iinteresting because of it's low depth and effectivity past 1khz as diffusor ( below 1khz it act as an absorber).
A rule of thumb for balanced sounding room is 1/3 absorbsion, 1/3 reflection, 1/3 diffusion ( in m2/ft2).
*absorber used is needed to have an idea of the freq range which have been overtreated. It will at turn decide of the bandwith ( the depth) needed for the diffusors.
The size of room ( and if possible layout) will help define the 'overall' lower freq reasonably possible hence the maximum depth of diffusors ( you need 3x time the lowest wavelength distance for the diffusor to be effective, bla, bla, bla,...
) .
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Aren't the absorbers panel removable?
I mean the simplest way to bring back a bit of liveness into the room is to discard a bit of it.
However not all and not anywhere:
Acoustic Treatment Setup 101: How to Treat Your Room
What Is A Reflection Free Zone (RFZ) In A Recording Studio?
– SoundAssured
This of course with use of diffusors.
I mean the simplest way to bring back a bit of liveness into the room is to discard a bit of it.
However not all and not anywhere:
Acoustic Treatment Setup 101: How to Treat Your Room
What Is A Reflection Free Zone (RFZ) In A Recording Studio?
– SoundAssured
This of course with use of diffusors.
I believe the panels are all 4" of 703 wrapped in grill cloth. I would guess the walls are probably 80% covered in panels. I don't know the exact dimensions but to me it's a pretty big room, 25x30' at least.
It's a finished basement with a roughly 12' ceiling but he had a drop ceiling installed a few years ago that's right at 10'6". He's never been happy with the way it looks and had been asking me about making some nice looking diffusers to partially hide the drop ceiling.
Hi,
80% of walls covered is way too much imho, at least not without other options taken too: if you want a dead room one have to stick to Hidley's 'zero environnement' principle but except if you use VPR absorber everywhere it usually sacrifice too much space for a domestic environnement. And one have to stand the resulting acoustic within the room too ( the one i heard was too much oppressive to my preference).
Like i said you have to estimate the overall surface presented by walls, ceilling and floor and then divide by 3 to have an approximation of what is needed approximately. With some config it is sometimes not possible ( floor is difficult to be other than reflective) but yet try ingto balance things is worth it imho.
As well, location of the panels matter.
I'm biased to a certain kind of rendering so take what i say with a grain of salt if your own preference vary with mine... but i would locate most absorbsion on first 1/3 of room length ( where are located the loudspeaker, 'frontwall' to me).
This way you can manage Early Reflection ( same principle as RFZ). And in this 1/3 i include the ceiling.
Could you draw a sketch of the drop ceiling ( or some pictures of the whole room) as i've got difficulties to understand how it's done ( and how you could hide this with diffusor too either if they could be of any significance performance wise)?
As the room is big you could use deeper design for the Shroeder qrd diffusor on backwall whith efficiency down to ~400hz ( for 30cm deep/1ft).
Of course you'll have noticed i should have said 2d and 1d rather than 3d and 2d in previous message... but you get the idea i hope!
Here is a link to a calculator to help estimate amount of damping required:
Acoustical Room Coverage Calculator
It is difficult to give advice without measruments but i've seen this applied multiple times ( 1/3 rot) and it cured most issue but rooms where way smaller: usually same mistake is made by enthousiat musician hoping for 'the best recording booth one can do'... always the same: by contrast ( as mid high are too damped) the modal behavior appear emphasized ( psychoacoustic 'masking effect' but the other way around) and completly lifeless environnement ( dull and oppressive).
80% of walls covered is way too much imho, at least not without other options taken too: if you want a dead room one have to stick to Hidley's 'zero environnement' principle but except if you use VPR absorber everywhere it usually sacrifice too much space for a domestic environnement. And one have to stand the resulting acoustic within the room too ( the one i heard was too much oppressive to my preference).
Like i said you have to estimate the overall surface presented by walls, ceilling and floor and then divide by 3 to have an approximation of what is needed approximately. With some config it is sometimes not possible ( floor is difficult to be other than reflective) but yet try ingto balance things is worth it imho.
As well, location of the panels matter.
I'm biased to a certain kind of rendering so take what i say with a grain of salt if your own preference vary with mine... but i would locate most absorbsion on first 1/3 of room length ( where are located the loudspeaker, 'frontwall' to me).
This way you can manage Early Reflection ( same principle as RFZ). And in this 1/3 i include the ceiling.
Could you draw a sketch of the drop ceiling ( or some pictures of the whole room) as i've got difficulties to understand how it's done ( and how you could hide this with diffusor too either if they could be of any significance performance wise)?
As the room is big you could use deeper design for the Shroeder qrd diffusor on backwall whith efficiency down to ~400hz ( for 30cm deep/1ft).
Of course you'll have noticed i should have said 2d and 1d rather than 3d and 2d in previous message... but you get the idea i hope!
Here is a link to a calculator to help estimate amount of damping required:
Acoustical Room Coverage Calculator
It is difficult to give advice without measruments but i've seen this applied multiple times ( 1/3 rot) and it cured most issue but rooms where way smaller: usually same mistake is made by enthousiat musician hoping for 'the best recording booth one can do'... always the same: by contrast ( as mid high are too damped) the modal behavior appear emphasized ( psychoacoustic 'masking effect' but the other way around) and completly lifeless environnement ( dull and oppressive).
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Quote from ndp:
"A friend of mine has been asking me about building him either some quadratic or skyline diffusers. He lined every wall in his listening space with acoustic panels and he's now decided he doesn't like how dull it sounds.
I purchased a book detailing the BBC designs of diffusers and figured that would be a good place to start."
May I be frank? Your friend doesn't know what to do, and neither do you.
My recommendation is for one of you to contact an acoustics products manufacturer which is familiar with this type of situation, or, to contact a room acoustics consultant who is familiar with 'small' rooms, particularly homes. I would also recommend that you be upfront with your friend and tell him that this is not your area of expertise.
"A friend of mine has been asking me about building him either some quadratic or skyline diffusers. He lined every wall in his listening space with acoustic panels and he's now decided he doesn't like how dull it sounds.
I purchased a book detailing the BBC designs of diffusers and figured that would be a good place to start."
May I be frank? Your friend doesn't know what to do, and neither do you.
My recommendation is for one of you to contact an acoustics products manufacturer which is familiar with this type of situation, or, to contact a room acoustics consultant who is familiar with 'small' rooms, particularly homes. I would also recommend that you be upfront with your friend and tell him that this is not your area of expertise.
Quote from ndp:
"A friend of mine has been asking me about building him either some quadratic or skyline diffusers. He lined every wall in his listening space with acoustic panels and he's now decided he doesn't like how dull it sounds.
I purchased a book detailing the BBC designs of diffusers and figured that would be a good place to start."
May I be frank? Your friend doesn't know what to do, and neither do you.
My recommendation is for one of you to contact an acoustics products manufacturer which is familiar with this type of situation, or, to contact a room acoustics consultant who is familiar with 'small' rooms, particularly homes. I would also recommend that you be upfront with your friend and tell him that this is not your area of expertise.
Thanks for the super helpful advice Dave. I appreciate your frankness. That being said.
Yes, neither of us know what to do, thats why I'm here, asking questions. I've never presented myself as a room acoustics expert, neither has my friend. I'm a farmer and carpenter by trade and my friend owns a pressure washing business, audio is something we do for fun, you know like a hobby.
Me being naive, I assumed that the DIY in DIY Audio stood for "do it yourself" not call the acoustics products manufacturer, or room acoustics consultant. Silly me wanting to learn to do something myself. We're not building a recording or mixing studio, it's a place to blast some tunes and throw down a few beers after a hard day's work.
Again thanks a ton for the super helpful info of calling the acoustic consultant, especially one that deals in 'small' rooms.
A consultant may be of great help but if it is for entertainment i fear the budget involved will kill the project before it happen.
If your goal are just to have a more confortable room don't bother: first start to dismantle some of the absorbers.
From the link i gave the recommended number of 8"x 4" panels for the room is 8. ( 16 if 4"x4").
From there you could improve things by using diffusors on the backwall.
Please shoot some pictures, draw a sketch of the room and you will have help from people here for sure.
With some chance involved you could even have some acoustical engineer taking part into the discussion too ( or people with enough knowledge to help even if they don't have the title anyway).
Given the situation there is no reason you can't upgrade the performance of this room imho.
Of course you'll have to learn some principle and rule of thumb along the way but it can be fun or at least interesting!
The fact you are a carpenter is nice as this is the main issue to build diffusors ( if you want them to not be to fugly!).
If your goal are just to have a more confortable room don't bother: first start to dismantle some of the absorbers.
From the link i gave the recommended number of 8"x 4" panels for the room is 8. ( 16 if 4"x4").
From there you could improve things by using diffusors on the backwall.
Please shoot some pictures, draw a sketch of the room and you will have help from people here for sure.
With some chance involved you could even have some acoustical engineer taking part into the discussion too ( or people with enough knowledge to help even if they don't have the title anyway).
Given the situation there is no reason you can't upgrade the performance of this room imho.
Of course you'll have to learn some principle and rule of thumb along the way but it can be fun or at least interesting!
The fact you are a carpenter is nice as this is the main issue to build diffusors ( if you want them to not be to fugly!).
Volumetric diffusers (= real 3D-diffusers) are quite easy to build and also less time consuming and expensive than Schroeder or skyline diffuser. You can pick your choice of material, wood / MDF / particle board etc.
If you google you can find ie:
(PDF) Volumetric Diffusers Check figure 13 which show the principle, a "layered fence" with varying slat widths, starting from small towards the room and then wider backwards towards the wall. The math behind is quite heavy to comprehend, a DIY-construction is not. Richard J Hughes wrote a thick document for his Ph D degree in acoustics on volumetric diffusers. I used some of his examples and wrote myself a spread sheet in excel to quickly customize 2 pcs in my room. (Have it on an old computer if I can find it in case anyone is interested.) For a truly wide band version, use the entire width of the room and let depth be something like 50-60 cm (20-24 inches.)
The picture shows 1 of my small ones (behind the horn): 5 layers, 30 cm / 12” deep and 70 cm / 27,5” wide, height 103 cm / 40,5”, slat width at front 35 mm / 1,38 " the last one at the back 143 mm / 5,6", -the largest I could fit in. If one attaches some LED strips behind the slats it can turn out rather nice aesthetically.
If you google you can find ie:
(PDF) Volumetric Diffusers Check figure 13 which show the principle, a "layered fence" with varying slat widths, starting from small towards the room and then wider backwards towards the wall. The math behind is quite heavy to comprehend, a DIY-construction is not. Richard J Hughes wrote a thick document for his Ph D degree in acoustics on volumetric diffusers. I used some of his examples and wrote myself a spread sheet in excel to quickly customize 2 pcs in my room. (Have it on an old computer if I can find it in case anyone is interested.) For a truly wide band version, use the entire width of the room and let depth be something like 50-60 cm (20-24 inches.)
The picture shows 1 of my small ones (behind the horn): 5 layers, 30 cm / 12” deep and 70 cm / 27,5” wide, height 103 cm / 40,5”, slat width at front 35 mm / 1,38 " the last one at the back 143 mm / 5,6", -the largest I could fit in. If one attaches some LED strips behind the slats it can turn out rather nice aesthetically.
Attachments
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Thanks for the info I'll definitely have a look at those documents. My buddy is now talking about wanting to take out the drip ceiling and do something completely different. Same with his walls. It's going to be a few weeks before I can get over to his place as he's currently recovering from a bout with COVID.
If I end up building something for my buddy I'm toying with the idea of building a few panels for myself. Although after doing a little bit more research I don't necessarily think my small space is suited for diffusion. My personal room is 12x15' with my speakers placed on the long wall. Directly behind my listening position is a large window that's got double layers of heavy thick curtains. As of now I've got a few DIY 705 corner traps placed on the speaker wall. I typically sit a few feet out from the wall behind me and have about a 7.5-8' equilateral triangle going on. It's not the best scenario but it works with my limited space and typical low level listening that I do.
I've wanted to try a live wall, dead wall setup in my room with the wall/window directly behind me being dead and floor to ceiling diffusion behind the speakers, running almost the total length of that wall. I'm going to have to do some more research and see what's feasible. But with my listening position being only 10' or so from that wall I have a feeling it might do more harm than good.
Anywhos thanks a ton for the replies guys. If we move forward with building a new drop ceiling at my buddies place, or if I go putting some floor to ceiling diffusion in my room I'll try and remember to post something about it here.
In general: Diffusers are placed behind you and possibly at the sidewalls behind first reflection points where resistive absorbers are place (or angeld reflectors towards the rear wall. Speaker wall: If soft = absorbtive, let the absorbtion be as deep as the speaker itself to kill the 1/4 wave SBIR from the front wall to "kill" the frequency dip from the reflection. (If the speaker is right up against the wall. SBIR = Speaker Boundary Interference Response). If a hard speaker wall and no absorbtion around, it is trickier to avoid a dip, you would need to flush mount the speaker baffles with the wall surface. -Easier written than done but usually seen as the best solution, if done right (easy to mess up though).
Exactly what I've been reading about. I might throw together a few more 703 or 705 panels, make them look good, to place directly behind
my speakers but I understand that it's honestly more of an aesthetics thing than it is functional at that point. My first reflection points are a bookshelf on one side and album storage/mini bar on the other side.
Honestly I don't do much "critical listening" I don't have the ears nor the space for it. I just really enjoy listening to some good tunes and having a nice comfortable place to unwind at the end of the day.
I've got another friend who's listening space is set up for critical listening. He hired someone to come do measurements, place panels all the proper stuff, probably spent $20k + just on room setup and treatments. There's only 3 seats in the room, matching leather chairs one in the "sweet spot" being flanked by the other two. While the sound in his room is pretty amazing it's not a fun place to hangout, **** there isn't anything for me to sit my cocktail down on as tables don't mesh with his acoustic treatments apparently.
Anywhos I'll try and keep this updated, and if he'll let me (he's funny about stuff like that, doesn't want pics of his gear out in the wild) I'll post some pictures of what we end up doing with the drop ceiling, and possibly some panels on his walls.
Yup, that would be way too dull sounding. I did end up removing some of the absorber panels from my room due to same problems, then added some diffuser panels, leaving some surfaces reflective. How the rest of the audio gear sounds should also dictate how much of what the room needs also.
For quick, cheaper diffuser experiments, I like the Pi audio diffusers:
PI audio group, LLC
Adhoc1,
Thank you for the paper.
I fully understand your friend doesn't want pictures of his place out in the wild: this is the same for me.
But you could make a 3d model with Sketchup for example.
You'll see this is handy and can bring some basic assumption about location of absorber panels ( even more if the directivity of loudspeaker is known) and diffusor.
I don't hink anyone needs golden ears to appreciate a good sounding room. It is even easier in the case of your friend as you don't seek for an 'absolute reference' sound, just bringing back some balance.
If you redo ceiling, angling can't be random. There is some basic rules to follow in order to redirect the ER outside the listening position ( usually to ward the backwall where diffusors are usually located).
To give you an idea food for thoughts:
http://downloads.bbc.co.uk/rd/pubs/reports/1995-04.pdf
For small space BAD panels are effective as difsorbers ( they acts as diffusors 1khz and above and absorbers below). 1khz wavelength is ~30cm/1ft so 3x 30cm=~1meter/3ft to be effective, if you space them from wall it'll increase the lower freq absorbtion too and as they are not this deep they are not to obstrusive.
As you are a carpenter maybe you could use hardwood with an heavy coat of varnish rather than metal sheet.
Infos are here:
US5817992A - Planar binary amplitude diffusor
- Google Patents
And i think i remember Adhoc built a variation around it with dots rather than square?
Yes i'm sure he did and find boring to drill so much holes! LOL ( we see one behind the 3d diffusor in the picture)
Thank you for the paper.
I fully understand your friend doesn't want pictures of his place out in the wild: this is the same for me.
But you could make a 3d model with Sketchup for example.
You'll see this is handy and can bring some basic assumption about location of absorber panels ( even more if the directivity of loudspeaker is known) and diffusor.
I don't hink anyone needs golden ears to appreciate a good sounding room. It is even easier in the case of your friend as you don't seek for an 'absolute reference' sound, just bringing back some balance.
If you redo ceiling, angling can't be random. There is some basic rules to follow in order to redirect the ER outside the listening position ( usually to ward the backwall where diffusors are usually located).
To give you an idea food for thoughts:
http://downloads.bbc.co.uk/rd/pubs/reports/1995-04.pdf
For small space BAD panels are effective as difsorbers ( they acts as diffusors 1khz and above and absorbers below). 1khz wavelength is ~30cm/1ft so 3x 30cm=~1meter/3ft to be effective, if you space them from wall it'll increase the lower freq absorbtion too and as they are not this deep they are not to obstrusive.
As you are a carpenter maybe you could use hardwood with an heavy coat of varnish rather than metal sheet.
Infos are here:
US5817992A - Planar binary amplitude diffusor
- Google Patents
And i think i remember Adhoc built a variation around it with dots rather than square?
Yes i'm sure he did and find boring to drill so much holes! LOL ( we see one behind the 3d diffusor in the picture)
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I might add some to the confusion, but here goes nothing, have a look at Folded Well Diffusors, since they do lower frequencies at a given build height. And for ceiling reflections one often needs quite low freq diffusion, whereas the available room may be limited.
