Polycylindrical Diffuser Design
Old 12th December 2010
  #1
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Polycylindrical Diffuser Design

Her is a paper about the subject matter who knows a thing or two about acoustics.

Andre
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Old 12th December 2010
  #2
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A lot has happened since then. The addition of temporal diffusion e.g. (not effectively achieved with polys).
Old 13th December 2010
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Quote:
Originally Posted by Jens Eklund View Post
A lot has happened since then. The addition of temporal diffusion e.g. (not effectively achieved with polys).
With all due respect, this thread is about polycylindrical diffuser design, as the title clearly states, NOT diffuser selection.

Please respect the, hoped for, purity of the thread.

Andre
Old 13th December 2010
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Pretty cool.
I never noticed the many-polys-making-one-large-poly idea before.

Kinda sorta like a diffractal, kinda.

Thanks, Andre.
Old 13th December 2010
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Andre,

Thanks for posting that.

For sake of future searches, here's a link to my poly build:

D. I. Y. Polys

It'd be nice to have a collection of sources on the matter.

I noticed that in many renderings of designs from your link, that polys are placed directly next to one another. I have read in several sources that these junctions of closely spaced polys can cause some focusing... and not the good kind of focus for the record. Has this understanding come after that particular paper was written, or is there something more at play here? I notice all of those pictures were of spaces of considerable size... perhaps this focusing effect has less negative impact in larger rooms?
Old 13th December 2010
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next thing you know, some mad person in a dank basement (or home theater) will be building poly diffractal units using a 4x8 sheet of 1/4" plywood bent 12" deep and a series of smaller 16" polys on that base poly using 1/8" plywood 4" deep. and the vertical units using 1/4" plywood 2x4 on a 6" deep bend and 1/8" polys on that using 3" deep bends.

madness i say!
Attached Thumbnails
Polycylindrical Diffuser Design-poly-diffractal-units.jpg  
Old 13th December 2010
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You, sir, are out of control.
Old 13th December 2010
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Quote:
Originally Posted by Mumblesound View Post
You, sir, are out of control.
i'm merely the messager

i do wonder though if the areas behind the small polys are solid or partially cut away?
Old 13th December 2010
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Quote:
Originally Posted by Mumblesound View Post
You, sir, are out of control.

+1 Nice sketchup work though, been admiring some of the slat type dealios. Definately giving some creative ideas.

I'd like to see some models of poly's off the boundaries without backing frame for more diffraction purposes-though it may be pushed to the (large) live room/ verb chamber.
Old 13th December 2010
  #10
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Thanks for the link, Andre. Not a huge fan of polys in general, but this gives me some good reading material on them.
Old 13th December 2010
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Quote:
Originally Posted by avare View Post
With all due respect, this thread is about polycylindrical diffuser design, as the title clearly states, NOT diffuser selection.

Please respect the, hoped for, purity of the thread.

Andre
Sorry, although I think it’s not a bad idea to point this out since a lot of people don’t realize the difference.

I’ll stay away from now on,
/Jens
Old 14th December 2010
  #12
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Thread Starter
Quote:
Originally Posted by johndykstra View Post
Andre,

Thanks for posting that.

For sake of future searches, here's a link to my poly build:

D. I. Y. Polys

It'd be nice to have a collection of sources on the matter.
You are welcome. Thank you for linking your build. It adds to the depth, pun intended, of the thread.

This thread may end up being a collection of poly sources. thumbsup

Quote:
I noticed that in many renderings of designs from your link, that polys are placed directly next to one another. I have read in several sources that these junctions of closely spaced polys can cause some focusing... and not the good kind of focus for the record. Has this understanding come after that particular paper was written, or is there something more at play here?
I think it is a combination of knowledge from experience and recording techniques back then included using a microphone for pickup, so variations near walls were not so significant. Also performers would not be plaed as close to partitiions as they are today.

Quote:
I notice all of those pictures were of spaces of considerable size... perhaps this focusing effect has less negative impact in larger rooms?
It is quite possible. Also they are not that deep, as in angle of the chords. The focusing would be less.

Well focused in nebullas,
Andre
Old 14th December 2010
  #13
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Thread Starter
Quote:
Originally Posted by gullfo View Post
next thing you know, some mad person in a dank basement (or home theater) will be building poly diffractal...
Thanks Glenn.

Madness takes its toll... Oops D'Antonio already does that.

Well bent,
Andre
Old 14th December 2010
  #14
Gear addict
 

poly example sharing

First,

Thanks for the link Andre. Our efforts today are built on strong shoulders and I appreciate you bringing forth studies like this.

Next, to Glenn (Guilfo)...I love that concept. I might run strips of 1" bonded cotton absorption on the flat portions and call it a day! A great day that is.

Attached is a "scratch track" room I designed in the residence of country star Billy Currington. It is anchored by the short lived but highly appreciated GIK Poly's...ehem, Glenn (GIK), bring them back if you can :-)

The room had a lo-mid resonance & his voice is all lo-mid. The use of the Poly's was key in the design. I like to combine absorption in a cluster with Poly's like on the ceiling: 6" wide 705 "rails" between the rows of Poly's
Attached Thumbnails
Polycylindrical Diffuser Design-dscn0112.jpg  
Old 14th December 2010
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very nice Jeff!
Old 14th December 2010
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I agree about the GIK poly.
I would have (eventually) bought a bunch of those.
Old 14th December 2010
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Since we have the Q7D pretty much in the bag, it is next on my list. Opps actually one more thing THEN it is on my list. Working on a diffusor that fits ceiling grid first.
Needless to say I think a poly design is pretty damn effective. I don't really understand (maybe marketing??) why some appose them. Can anyone think of a case where a designer put them in a room then removed them because of it f'ing up the room? Or has anyone been in a room with them and thought it sounded out of whack??
Old 14th December 2010
  #18
SAC
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Note details regarding the performance of polys.

Acoustic Diffusers: The Good, the bad and the ugly
Trevor Cox.
Old 14th December 2010
  #19
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Thanks Glenn (Guilfo)

And, to Glenn (GIK). Yes actually...there is a CR that does some really nice records I've worked in as bass player. It's owned by well respected producer/guitarist. The rear wall has carpet and three large poly's mounted (nothing else). One is center located about 4'x8'x12" and the other two are approx third smaller and flank the center location...not good at all. I don't blame the poly's, I blame the design purpose. I would pull those out in a second. That room is pretty large approx 4K cu ft.
Old 14th December 2010
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jwl
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For me, it's not a question of whether polys suck or are good. It's a matter of degree. Polys are generally better than a flat wall, but there are more effective choices.

See RealTraps - All About Diffusion
Old 14th December 2010
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Old 15th December 2010
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Great thread Andre.

Here is my 'take' on polys.

Cheers,
John
Attached Files
File Type: pdf Poly Panels.pdf (171.4 KB, 1319 views)
Old 15th December 2010
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For me, totally a matter of cost. Poly's are a very cost effective and pleasurable method for live performance treatment.

In a control room, the effective difference with what a more mathematical and temporal device offers puts it as "worth the money".

A laymen's novice +.02
Old 15th December 2010
  #24
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Thumbs up

Quote:
Originally Posted by jhbrandt View Post
Here is my 'take' on polys.
And here they are in action... Oh and Mr Brandt, my electricity is finally finished!

Great thread Andre! Oh and if you run in to Bryan Adams over there, could you tell him that i still got Mickey's (Michael curry) drum stick and if he's missing it sorely, he can give me a call.

Cheers,
Attached Thumbnails
Polycylindrical Diffuser Design-img_0416.jpg   Polycylindrical Diffuser Design-img_0417.jpg   Polycylindrical Diffuser Design-img_0418.jpg   Polycylindrical Diffuser Design-img_0419.jpg   Polycylindrical Diffuser Design-img_0421.jpg  

Polycylindrical Diffuser Design-img_0422.jpg   Polycylindrical Diffuser Design-img_0413.jpg   Polycylindrical Diffuser Design-img_0423.jpg   Polycylindrical Diffuser Design-img_0427.jpg   Polycylindrical Diffuser Design-img_0424.jpg  

Old 15th December 2010
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Very nice Sören. Can I useyour photos in my docs?

Cheers,
John
Old 16th December 2010
  #26
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Smile

Thank you Mr Brandt,

Yes, you can certainly use my photos. I would consider it an honor and a privilege. E-mail is on the way...


Cheers,
Old 17th December 2010
  #27
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RE SAC's link

Although this is a poly discussion, SAC's link to Acoustic Diffusers: the good, the bad and the ugly made mention of single asymmetric base shape diffusors (Fig #6). I'm happy to start a new thread on this but would first like to know if anyone has used, specified, built anything as described in the doc?? If so, is there enough interest in starting a discussion??

Thanks.

JV
Old 17th December 2010
  #28
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Quote:
Originally Posted by JVergence View Post
Although this is a poly discussion, SAC's link to Acoustic Diffusers: the good, the bad and the ugly made mention of single asymmetric base shape diffusors (Fig #6). I'm happy to start a new thread on this but would first like to know if anyone has used, specified, built anything as described in the doc?? If so, is there enough interest in starting a discussion??

Thanks.

JV
Maybe not exactly what you’re after but this thread might be of interest:

QRD and Skyline Well Dividers?
Old 18th December 2010
  #29
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Poly construction idea

Quote:
Originally Posted by jhbrandt View Post
Here is my 'take' on polys.

Cheers,
John
Based on information gleaned here and from other sources, this is a poly diffusor / bass trap I am proposing to build. The criteria is that the panel be as cost and build-time effective as possible, have the ability to be free hung as a temporary installation 2+ inches from the wall (most likely by chain), and be portable enough so that I can take them with me when I move from the room that I am now renting. The intention is to create a relatively live ambience for drum tracking, while at the same time achieving as much low end absorption as possible.

The approximate overall dimension of the panel is 7' x 4' x 10". Trapping would consist of 6' x 2' x 4" of unfaced OC 703, stuffed inside the framing without touching the front face. Rather than using wood for the face, I am going to try using a material called Coroplast (4mm), which is a durable, lightweight, flexible corrugated polypropylene copolymer (imagine corrugated cardboard, but made out of plastic). The reason for this is that it's relatively cheap, very lightweight, is much easier to form/bend than wood, and doesn't have the fundamental resonate note that wood has when taut (think of the thud of a muffled kick drum).

Coroplast

The room is fairly large (700+ sq. ft.) and instruments can be placed 8+ ft. from walls without much problem, so hopefully the artifacts usually caused when too things are placed too close to polys won't be an issue. The plan is to build 6 of these to be used in conjunction with superchunk corners, a few ceiling clouds, as well as a handful of tube traps that I have.

Any suggestions or thoughts on the specific approach (as opposed to the much larger pro/con poly discussion) would be welcome.
Attached Thumbnails
Polycylindrical Diffuser Design-poly-diff-trap-view-1.jpg   Polycylindrical Diffuser Design-poly-diff-trap-view-2.jpg   Polycylindrical Diffuser Design-poly-diff-trap-view-3.jpg   Polycylindrical Diffuser Design-poly-diff-trap-view-4.jpg  
Old 18th December 2010
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it looks like its about 1/3 to 1/4 the density of plywood and may not be as reflective as it is absorptive...
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