polycylindrical diffusers

[RKrizman]

Have they been discussed to death here already? In the other forum some detail came up about squeezing 1/4' masonite or plywood between two studs to make it bow out about 6". Useful for diffusion and bass trapping. It seems really easy to do. I know SAC will say that it all needs to be specific to your needs, but I'm curious if anybody has opinions or construction techniques to share about these.

Airtight or open? Stuffed or hollow? I saw Ethan's video unfavorably comparing polys with his well diffusor, but those were a series of polys, which apparently presents problems.

Sorry if this is a tired subject, but if these are effective it could provide easy solutions to a lot of problems.

-R

[avare]

Search for polys and you find at least one thread that that became almost exclusively about polys. One of the easiest ways to bend and make is detailed by the late (great) Malcolm Chisholm. Search for his name and website kept up. Did I mention that Malcom was great?

Andre

[dykesh]

I just made two polys in the back corners on my room. My room is 8'-3" from the floor to the bottom of the floor trusses that are overhead in my basement. I took 6"D x 2'W x 8'H of 705 equivilent rockwool and straddled the corner and strapped it to the walls. Then I took a couple of 1"x2"x6' pieces and spaced them 46.5" apart across the corner. I laid a 2x4 on the floor and set a 2'x4'x8' piece of masonite on that vertically and curved it into place. That way I had a 1.5" air gap at the bottom and at the top near my trusses. It worked great but it was very hard to bend. I could only find 3/16" masonite so it was a little thicker. I also sprayed just a little water on the back of the masonite to get a little softer. I have not finished my room so I have not done any testing yet but it does seem to sound like more diffusion and still bass trapping.

[PaulP]

Originally Posted by dykesh

I have not finished my room so I have not done any testing yet but it does seem to sound like more diffusion and still bass trapping.

It might be better to test as you go. That way you'd see if a particular
treatment did anything useful or not. If you're not satisfied once your room
is done it could be difficult to figure out what needs changing if you don't
know what each part is doing.

Paul P

[MJGreene Audio]

Originally Posted by RKrizman

Have they been discussed to death here already? In the other forum some detail came up about squeezing 1/4' masonite or plywood between two studs to make it bow out about 6". Useful for diffusion and bass trapping. It seems really easy to do. I know SAC will say that it all needs to be specific to your needs, but I'm curious if anybody has opinions or construction techniques to share about these.

Airtight or open? Stuffed or hollow? I saw Ethan's video unfavorably comparing polys with his well diffusor, but those were a series of polys, which apparently presents problems.

Sorry if this is a tired subject, but if these are effective it could provide easy solutions to a lot of problems.

-R

Put a wall of them on my live room. It helps to smooth it out quite well. Open on top and bottom with insulation inside. 4 feet wide 8 feet tall. Plywood back with 1x2 pieces on the edges. Oak plywood for the fronts.

In my previous studio build and also on this one I tried panels made from Luan boards. The issue I had is that the stock of Luan that Home Depot sells are always different. When I was putting this together I built two at home and the Luan panels bent in just fine. Nice and easy. When I went to build these I bought 4 more sheets and found out it was a different supplier and the panels would not bend enough. I ended up breaking a panel after trying to get it to bend and suck in. I looked again and found them to be entirely different stock. Went back and found the oak plywood that was actually thicker but bent like butter. All 4 panels went together fast and easy. Then the only problem I had was they were actually to flimsy and wouldn't stay in place. I put finish nails all along the sides from top to bottom to secure them in place and keep them from rattling. Worked out well. A little stain and they look fantastic.

I have always loved the look of Poly's and they do work. Maybe not the same way as other diffusors but for the cost versus size they do the job well.

Not an expert but it works so for me its a no brainer.

The room is 23X 19 with 13 foot ceilings. Give them a try. Fairly cheap to build.

Michael Greene

[RKrizman]

Very nice looking room. Thanks for the tips.

-R

[PaulP]

Very inspiring !

Paul P

[MJGreene Audio]

Originally Posted by PaulP

Very inspiring !

Paul P

Thanks guys. Its been fun putting it together.

Michael Greene

[Glenn Kuras]

I saw Ethan's video unfavorably comparing polys with his well diffusor, but those were a series of polys, which apparently presents problems.

The only thing that video proves, which he is totally right is polys don't work well when only 2 to 6" from the mic (or your ears). Totally different story when you get say 5 feet or so from it.

[RKrizman]

Originally Posted by Glenn Kuras

The only thing that video proves, which he is totally right is polys don't work well when only 2 to 6" from the mic (or your ears). Totally different story when you get say 5 feet or so from it.

I also understand it's not great to put them right next to each other like that.

-R

[Brent Hahn]

Originally Posted by avare

One of the easiest ways to bend and make is detailed by the late (great) Malcolm Chisholm.

Couldn't find it, so here's my way: Cut a bunch of 1/8" longitudinal grooves into the back of the panel with a Skil saw, about 3 or 4" apart.

[Glenn Kuras]

Originally Posted by RKrizman

I also understand it's not great to put them right next to each other like that.

-R

It does depend, but we do a lot of rooms with poly then a absorber right next to that. Like I said though it all really depends.

[johndykstra]

I started building some a while ago. THe prototype came out very well, and after my clamping jig was fabricated, the build is quite easy. Here's a link to the thread containing the process:

Photo journal of remodel: polys, clouds, & traps (was: a work in progress)

I plan to start a new thread dedicated to them when I get around to building the other 8 or so planned for the space.

[avare]

Originally Posted by Brent Hahn

Couldn't find it, so here's my way: Cut a bunch of 1/8" longitudinal grooves into the back of the panel with a Skil saw, about 3 or 4" apart.

Here is the link right to the article detailing the construction method.

http://malcolm.bignoisybug.com/rsdp/fuzpoly.txt:


Andre

[Glenn Kuras]

Originally Posted by dykstraster@gmai

I started building some a while ago. THe prototype came out very well, and after my clamping jig was fabricated, the build is quite easy. Here's a link to the thread containing the process:

Photo journal of remodel: polys, clouds, & traps (was: a work in progress)

I plan to start a new thread dedicated to them when I get around to building the other 8 or so planned for the space.

Wow you did a great job on those. thumbsupthumbsup

[Lonely Raven]

Keeping in mind that you need to be some distance away from the polys for them to be effective (just as with any broadband scattering unit), and that you plan for the hot spots putting them next to each other can create...the only other drawback you need to keep in mind, is that polys don't alter the arrival time of the scattered sound like proper diffusers do. If that suits your needs, then polys rock with simplicity and can look really nice.

[avare]

Originally Posted by Lonely Raven

Keeping in mind that you need to be some distance away from the polys for them to be effective

Wrong. Ploy type diffusers do not have a minimum distance for effectiveness.

and that you plan for the hot spots putting them next to each other can create..

Correct. Do not put right against one another.

.the only other drawback you need to keep in mind, is that polys don't alter the arrival time of the scattered sound like proper diffusers do. If that suits your needs, then polys rock with simplicity and can look really nice.

Wrong. The pure spectral diffusion of a poly is characteristic of its acoustic performance. It is neither a advantage or disadvatage. It is feature of them, whether is diserable or not depends on the specific application.

Andre

[johndykstra]

Originally Posted by Glenn Kuras

Wow you did a great job on those. thumbsupthumbsup

Thanks Glenn!

[Glenn Kuras]

Originally Posted by avare

Wrong. Ploy type diffusers do not have a minimum distance for effectiveness.


Correct. Do not put right against one another.


Wrong. The pure spectral diffusion of a poly is characteristic of its acoustic performance. It is neither a advantage or disadvatage. It is feature of them, whether is diserable or not depends on the specific application.

Andre

thumbsupthumbsup

[Brent Hahn]

Originally Posted by avare

Here is the link right to the article detailing the construction method.

http://malcolm.bignoisybug.com/rsdp/fuzpoly.txt:


Andre

Thanks - great stuff! The article on live chamber construction is good, too. Love his pragmatism and writing style.

[Schaap]

Originally Posted by dykstraster@gmai

I started building some a while ago. THe prototype came out very well, and after my clamping jig was fabricated, the build is quite easy. Here's a link to the thread containing the process:

Photo journal of remodel: polys, clouds, & traps (was: a work in progress)

I plan to start a new thread dedicated to them when I get around to building the other 8 or so planned for the space.

I missed that thread too. Nice job, great how those poly's look.

[avare]

Originally Posted by Brent Hahn

Thanks - great stuff! The article on live chamber construction is good, too. Love his pragmatism and writing style.

You are welcome. Malcolm was great.

Andre

[PaulP]

Originally Posted by Lonely Raven

...the only other drawback you need to keep in mind, is that polys don't alter the arrival time of the scattered sound like proper diffusers do.

In a way they do, except for the sound that bounces off a very thin slice of
the poly that is directly facing you. All the rest gets sent off in different
directions and by doing so will arrive later.

Paul P

[Bob Olhsson]

My personal experience has been that studios employing Polys sound lots better than studios employing so-called "proper" diffusers.

In fact I think most studios designed since the early 1960s by even the biggest "names" totally suck. Control rooms have come a long way but the folks designing studios have obviously never spent any time in a great one.

[Glenn Kuras]

Originally Posted by Bob Olhsson

My personal experience has been that studios employing Polys sound lots better than studios employing so-called "proper" diffusers.

In fact I think most studios designed since the early 1960s by even the biggest "names" totally suck. Control rooms have come a long way but the folks designing studios have obviously never spent any time in a great one.

I don't know Bob I am sure there are some strange sounding studios out there but I really think there are many more tools (as in products) which should give designers more opportunity for better sound. A big part of the reason for us opening up our custom shop. The ski is the limit, if you know what I mean. But with that said I got a QRD not so long ago without the fins and to be honest liked what it did with the sound much better then QRDs with fins. It seems to almost "widen" the sound much more.

[Weasel9992]

Originally Posted by avare

Correct. Do not put right against one another.

Jeff Hedback, one of the designers we work with all the time, suggests putting something soft between polys to reduce or eliminate audible pinging artifacts.

Frank

[nosebleedaudio]

Originally Posted by Weasel9992

Jeff Hedback, one of the designers we work with all the time, suggests putting something soft between polys to reduce or eliminate audible pinging artifacts.

Frank

I would just space them around 2 to 3 feet apart, I would never put them side by side..
I designed a Poly a while back that was also a bass trap, looks very cool as well..

My .02cents

[Lonely Raven]

Originally Posted by avare

Wrong. Ploy type diffusers do not have a minimum distance for effectiveness.

I was under the understanding that since a poly effects a wide band of sound, there is a distance required for the wider frequencies. It would be similar to having a 1D QRD with a recommended minimum distance of 6', but being within 5' (just an arbitrary example). Yes they work across many frequencies, but the broader they are, the further you need to be for the *full* effect. (I hope that made sense)

Originally Posted by avare

Wrong. The pure spectral diffusion of a poly is characteristic of its acoustic performance. It is neither a advantage or disadvatage. It is feature of them, whether is diserable or not depends on the specific application.

Andre

That's what I thought I said.

I need more coffee before I write I guess.

[vespiz]

Originally Posted by Weasel9992

Jeff Hedback, one of the designers we work with all the time, suggests putting something soft between polys to reduce or eliminate audible pinging artifacts.

Frank

So.. for instance, a checker-pattern with alternating polys and absorption would be ok?

I'm looking into some design ideas for the (so-called) live room.

[Glenn Kuras]

Originally Posted by vespiz

So.. for instance, a checker-pattern with alternating polys and absorption would be ok?

I'm looking into some design ideas for the (so-called) live room.

That would work fine