2-D QRD Diffusors

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2-D QRD Diffusors

Postby archive » Mon Apr 12, 2004 4:15 am

From: Brendan Minish <bminish@o...>
Date: Wed Jan 26, 2000 2:32 pm
Subject: 2-D QRD Diffusors

I Would like to build some 2-D QRD diffusers for the back wall of my
control room, I am interested in having good diffusion above about
350-400Hz (Size restrictions will prevent me going much below 350Hz)
I can find plenty of good information about building 1-D QRD diffusers but
virtually nothing about 2-D QRD Diffusers, I am Particularly Interested in
the 2-D designs as they will give me greater diffusion than the 1-D designs.
The back wall of my control room is only about 8 feet from my head so
maximizing the amount of diffusion is important.
--

Brendan Minish
bminish@o...
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Postby archive » Mon Apr 12, 2004 4:18 am

From: Dan Nelson <dprimary@e...>
Date: Thu Jan 27, 2000 5:36 pm
Subject: Re: 2-D QRD Diffusors

I have some 2D omniffusers in my control room, I could measure them for you if
that would help. It will take me about a week to have time to put them in a
drawing. I'm moving today.

Dan Nelson
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Postby archive » Mon Apr 12, 2004 4:19 am

From: Brendan Minish <bminish@o...>
Date: Thu Jan 27, 2000 5:52 pm
Subject: Re: 2-D QRD Diffusors


That would be very helpful, There is no Hurry as I am having 4 wisdom teeth
removed in a few days and I expect that I won't be in much Humor for
Carpentry for a couple of weeks.
Good luck with the move, I hope you find more stuff than you loose.

Do you find the 2D omniffusers work well?
Have they helped with the Stereo Imaging?
I guess you have them behind the mix position?
--

Brendan Minish
bminish@o...
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Postby archive » Mon Apr 12, 2004 4:19 am

From: SRF7@a...
Date: Thu Jan 27, 2000 11:39 pm
Subject: Re: 2-D QRD Diffusors

In a message dated 1/26/00 9:34:07 AM Eastern Standard Time,
bminish@o... writes:

> I Would like to build some 2-D QRD diffusers

Very Cool!

How are you going to build them?

Something like an array if these babies?

<A HREF="http://www.sysdevgrp.com/products/modele.html">http://www.sysdevgrp.c
om/products/modele.html</A>

Tell us more.

Scott
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Postby archive » Mon Apr 12, 2004 4:19 am

From: Brendan Minish <bminish@o...>
Date: Fri Jan 28, 2000 1:47 am
Subject: Re: 2-D QRD Diffusors

At 18:39 27/01/00 -0500, you wrote:
>From: SRF7@a...
>
>Very Cool!
>
>How are you going to build them?

Probably out of MDF and thin (0.5mm thick) steel but I am open to
suggestions, I am going to do some experimenting with High Density foam
Insulation as well.

>Something like an array if these babies?
>
>http://www.sysdevgrp.com/products/modele.html

I hadn't seen this particular design until now, the Only design I was aware
of was the RPG Systems Ommnifusor type see.
http://www.rpginc.com/products/omniffus/omniffus.htm

>Tell us more.

I will when I work it out! I was hoping that someone Else here Would be
able to tell me more, Most of what I know about them comes from an AES (
http://www.aes.org/ ) Preprint (2938) called 'The QRD Diffractal: A new 1
or 2 dimensional Fractal Sound Diffuser.' By Peter D'Antonio and John
Konnert of RPG systems limited.
I am not an AES Member but anyone can order re-prints of papers etc from
them, It's a very good resource for all sorts of audio related Information.
The devices talked about in the paper involve building High frequency
diffusion inside low frequency diffusion (Hence the reference to Fractals)
I haven't really got room for the low frequency diffusion (requires too
great a well depth) so I'll settle for good diffusion above 400 Hz or so
(Which should give me some diffusion down to 250Hz or so.
I May add some lower frequency diffusion to the ceiling if I need to.

--

Brendan Minish
bminish@o...
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Postby archive » Mon Apr 12, 2004 4:20 am

From: Mattias Henningson <mattias.henningson@d...>
Date: Fri Jan 28, 2000 6:42 am
Subject: RE: 2-D QRD Diffusors

Hello all!

I've never posted on this list before so maybe it's appropriate with a
short introduction. I'm a musician, live in Sweden, play alot with
different people and I also run a small studio as a side project (so
far) to my day job as a software architect. Enough rambling...

On the topic - there's another source for 2-d diffusors that I didn't
know about until just the other week. Like Brendan I've tried to find
some information regarding building 2d diffusors without any luck.

On http://hem.passagen.se/akustik/index.html you'll find some more info
on that company and their products.

/Mattias
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Postby archive » Mon Apr 12, 2004 4:20 am

From: Jeanine Cowen <jcowen@m...>
Date: Fri Jan 28, 2000 11:55 am
Subject: Re: 2-D QRD Diffusors

>> I Would like to build some 2-D QRD diffusers
>
>http://www.sysdevgrp.com/products/modele.html
>

You may want to consider buying the ETF Acoustic measurement package from

http://www.etfacoustic.com

He's got a device designer in there for quadratic residue diffusers that
may be helpful...

JC
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Postby archive » Mon Apr 12, 2004 4:20 am

From: Brendan Minish <bminish@o...>
Date: Fri Jan 28, 2000 12:42 pm
Subject: Re: 2-D QRD Diffusors

At 06:55 28/01/2000 -0500, you wrote:
>From: Jeanine Cowen <jcowen@m...>
>
> >> I Would like to build some 2-D QRD diffusers
> >
> >http://www.sysdevgrp.com/products/modele.html
> >
>
>You may want to consider buying the ETF Acoustic measurement package from
>
>http://www.etfacoustic.com

I have done already, and very good it is too, although I find myself using
SIA smaart Pro for most of my measurements these days.

>He's got a device designer in there for quadratic residue diffusers that
>may be helpful...

These devices are similar BUT they are One dimensional

--

Brendan Minish
bminish@o...
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Postby archive » Mon Apr 12, 2004 4:22 am

From: "LEIF HOLE" <ingrid-leif@c...>
Date: Fri Jan 28, 2000 7:18 pm
Subject: Re: 2-D QRD Diffusors

Have you heard about Ecoprim ?

This is a highdensity *foam* they use to isolate road with in Norway. Its hard,
and very easy to cut and paint (comes in pink and light blue).
And very light, it can be glued to the wall !
Its cheap, and you get it in different thickness. 3-5-7-10 cm. Size 60 cm x 240
cm.
But it burns easy.
I have used it for normal PRD in my studio an works very well.

Leif Hole
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Postby archive » Mon Apr 12, 2004 4:23 am

From: SRF7@a...
Date: Sat Jan 29, 2000 6:16 am
Subject: Re: 2-D QRD Diffusors

In a message dated 1/27/00 8:48:47 PM Eastern Standard Time,
bminish@o... writes:

<< RPG Systems Ommnifusor type see.
http://www.rpginc.com/products/omniffus/omniffus.htm >>

You might want to check the article by Angus on mixing quadratic residue
sequences to improve diffuser performance. I think it was in the AES Journal
in late '98. His ideas would probably help that blocks in a coke crate
design enormously.

Scott R. Foster
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Postby archive » Mon Apr 12, 2004 4:31 am

From: "Dan Nelson" <dprimary@h...>
Date: Thu Feb 3, 2000 2:52 am
Subject: 2d diffusors

John P. Sexton has sent me an ACAD .dwg file of a 2d diffusor. I have posted
it in the file area. I will try to convert get it into a jpg or pdf so
everyone can view it.

Dan Nelson
Scott can you take a shot at it or convert it into a .dxf file?
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Postby archive » Mon Apr 12, 2004 4:33 am

From: SRF7@a...
Date: Thu Feb 3, 2000 12:06 am
Subject: Re: 2d diffusors

In a message dated 2/2/00 2:54:15 PM Eastern Standard Time,
dprimary@h... writes:

>
> John P. Sexton has sent me an ACAD .dwg file of a 2d diffusor. I have
posted
>
> it in the file area. I will try to convert get it into a jpg or pdf so
> everyone can view it.
>
> Dan Nelson
> Scott can you take a shot at it or convert it into a .dxf file?

Youbetcha

Scott
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Postby archive » Mon Apr 12, 2004 4:33 am

From: "Dan Nelson" <dprimary@h...>
Date: Thu Feb 3, 2000 8:26 am
Subject: 2Dfusor

A gif of John's 2d diffusor drawing is up in the file area or this link
http://www.studiotips.com/files/2Dfusor.gif

John is this based on a RPG diffusor? The ones in my control room have 7
well depths they are the cast plaster ones.
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Postby archive » Mon Apr 12, 2004 4:34 am

From: "John P. Sexton" <jsexton@c...>
Date: Thu Feb 3, 2000 6:52 pm
Subject: re:2Dfusor

>John is this based on a RPG diffusor? The ones in my control room have 7
>well depths they are the cast plaster ones.

>Dan Nelson
>______________________________________________________

It's based on one that I borrowed from someone to measure. ;) But the outside
dimensions turned out to be the same as the RPG Omnifusor with the difference
being the well depths seem to have the middle and empty one's reversed. I drew
it exactly as it is because I can't verify if those two well depth's are
reversed on purpose or not and the one I measured seem's to work just fine as
is. I've seen pictures of the pattern both ways so I guess either one work's

John P. Sexton
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