Round Shape Diffusors & alternative

[Tony76]

Hello!

I actually have 2 questions, so i would start from asking about round shaped diffusers, like this: http://www.audiostop.ru/examples/bondarchuk/23-sm.jpg
http://www.audiostop.ru/examples/bondarchuk/31-sm.jpg

How useful are they, and how they are actually called? I was thinking about building over the "drum" wall using them, but unfortunately have'nt found anything about the frequencies features. Any calculators would be probably very useful!

Question No. 2:
As alternative to those rounded diffusers, i also thought about making it simply curved, using wooden plates. I'll better show you on pic...

Here are wooden panels placed at various angels. Eaches plate's dimensions are aprox. 0,85x1,5 m
ImageShack - Hosting :: drwallbg4.gif
The walls dimensions are: L 5,35m, H 2,8m.

It seems to be very ineteresting looking and (hopefully) sounding wall. But how it's in fact?...

P.S sorry for my English!
P.P.S i gonna also convert the meters to ft. tomorrow

Thanks,
Tony

[Ethan Winer]

Originally Posted by Tony76

i would start from asking about round shaped diffusers

Those are called "polys" which is short for polycylindrical. I'm not a fan of those in small rooms, but they are okay in large rooms. You can hear a comparison of QRD and poly diffusors in the video All About Diffusion, partway down the list on my company's RealTraps Videos page.

--Ethan

[Tony76]

My room is about 45 sq meters (~485 sq ft), 130 m3 (4600 ft3). For your opinion, is it big enough for poly diffusers, and what could you say about the second variant?

[nosebleedaudio]

If I used Polys I would not have them next to each other, a 2 foot space would be better.
And with all diffusors several feet away is better, 8 to 10 feet.
I designed a large one for the back wall of a CTR, it was 5 feet by 5.5 feet and 14" deep.
Centered on the rear wall...
Looks very cool and is used for bass trapping as well...

[Weasel9992]

Originally Posted by Tony76

My room is about 45 sq meters (~485 sq ft), 130 m3 (4600 ft3). For your opinion, is it big enough for poly diffusers, and what could you say about the second variant?

You're getting to the point where poly's could be useful. Whether they're appropriate or not depends on the exactly problem you're trying to solve.

Frank

[Tony76]

Currently, i dont have any problems, i'm simply projecting the room acoustic, just the drum wall.

All walls will be covered by fabric. My idea of drum room was making semi diffusing, semi reflecting. But here i am for advice about which type of diffusion in my case is better.

Here's the room's plan.

[matt thomas]

correct me if I'm wrong but round diffusers aren't diffusers at all, they are dispersers..

narco

[andrebrito]

they are diffusers.... they diffuse sound in space.

A sound disperser is an audio system having an output which is varied by a rotating disc.

And sound dispersive medium in one where speed of sound changes with frequency

[Glenn Kuras]

Originally Posted by Weasel9992

You're getting to the point where poly's could be useful. Whether they're appropriate or not depends on the exactly problem you're trying to solve.

Frank

I would agree and for a drum room it should work VERY well. Actually I think if you have around 5 feet from them they work pretty well. So even in a smaller room they could be useful.

Glenn

[Tony76]

I cant find any poly's diagrams and sizes. Someone?

[Tony76]

How does the radius depend on absorbed/diffused sound?

What's the recomended plywood thickness?

[avare]

Originally Posted by Tony76

How does the radius depend on absorbed/diffused sound?

This thread will help answer that.

What's the recomended plywood thickness?

It depends on what frequency range absorption you want. Adjust the volume for an equivalent depth and use membrane absorber equations.

Andre

[Tony76]

Thanks,

I found someone's reыуфкср about the membran absorbetion. and found this equation as conclusion of this research (atached below). Anybody can say something about that?

t - thickness
Pa - Mass per area

[avare]

Originally Posted by Tony76

Thanks,

I found someone's reыуфкср about the membran absorbetion. and found this equation as conclusion of this research (atached below). Anybody can say something about that?

t - thickness
Pa - Mass per area

That is the metric version. The imperial (lb/ft^2 and inches units) uses 170 as the constant.

Andre

[Tony76]

I live in EU so metric is suitable for me

I just now wonder how does all those equations work?

For example, i counted that i am able to make myself polydiffuser with area of 1kg/m^2, with 12 cm thickness in the widest point. In this case, i got number "179" from this equation. Is that the peak of possible absorbetion? If it is, what's the coefficient of the absorption? How can i count it?

[solo-bration]

Tony are you still out there? If so, did you end up using polys and if so how were the results? Any pics? I ask, because I have a similar sized live room I'm considering using polys in.

[matt thomas]

Originally Posted by andrebrito

they are diffusers.... they diffuse sound in space.

A sound disperser is an audio system having an output which is varied by a rotating disc.

And sound dispersive medium in one where speed of sound changes with frequency

Hey, you replied to me three years ago, but I have only just seen it due to someone bumping this thread recently. Thanks, I did a bit more research after your comment, as my understanding was based on what I had read on various forums (out of interest, and in my defence , from a quote on gearslutz):

True diffusion is different from scattering. Putting up some rough things or a poly-cylindrical will indeed scatter, but not diffuse. Diffusion also spreads in time, not only space, and is mathematically designed to provide very even dispersion over a certain frequency range, rather than the unpredictable, limited, and uneven response of simple scattering surfaces.

to which ethan winer replied:

I nominate this for 2007 Post Of The Year, and I'll link to this every time some bozo says a poly is as good as or better than a real diffusor.

but looking into it a bit more I would have to agree that both spatial diffusion (as in a poly) and temporal diffusion (as in a QRD) are both types of diffusion, with the QRD typically being more effective.

cheers
matt (ex narco)