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Author Topic: D.I.Y. Diffusers  (Read 43709 times)

rdolmat

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D.I.Y. Diffusers
« on: September 27, 2005, 11:59:05 am »

Hi all!

Anyone have good tips or suggestions on DIY diffusers? I'd like to throw some up on my rear wall but don't want to pay $150 for 1 molded plastic tile!! What a rip-off!

Maybe a good junk store has some weird looking tile thing that can be a diffuser? Cool
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Cheers
rich

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compasspnt

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Re: D.I.Y. Diffusers
« Reply #1 on: September 27, 2005, 12:12:00 pm »

You can certainly make your own, but to work properly they must be built according to certain acoustic principles related to the laws of physics as they relate to sound waves (remember science?  some here seem to be ignoring it).

Surely someone here knows of a good book whioch relates such things.

Egg cartons won't do it.


http://www.acousticsfirst.com/articles/diskmakers/index.htm
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Eric Bridenbaker

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Re: D.I.Y. Diffusers
« Reply #2 on: September 27, 2005, 12:27:50 pm »

compasspnt wrote on Tue, 27 September 2005 12:12

You can certainly make your own, but to work properly they must be built according to certain acoustic principles related to the laws of physics as they relate to sound waves (remember science?  some here seem to be ignoring it).

Surely someone here knows of a good book whioch relates such things.

Egg cartons won't do it.


http://www.acousticsfirst.com/articles/diskmakers/index.htm

The hard part is to get the diffusion to happen evenly across the spectrum. Overly symmetrical patterns will tend to favor only a certain set of frequencies, breaking up/randomizing the physical pattern of the diffuser helps a lot.

Bookcases (filled with books) tend to have nice diffusion properties.

Check out the RPG site for ideas on how they approach their designs, and also some of the math that goes into creating even sound redistribution:

http://www.rpginc.com/proaudio/index.htm

Also here:

http://www.audioholics.com/techtips/roomacoustics/RPGdiffuse rs.php

Of course, every case is different, a good acoustician will be able to let you know if you're on the rght track.

Best,
Eric
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blairl

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Re: D.I.Y. Diffusers
« Reply #3 on: September 27, 2005, 12:29:48 pm »

rdolmat wrote on Tue, 27 September 2005 09:59

Anyone have good tips or suggestions on DIY diffusers? I'd like to throw some up on my rear wall but don't want to pay $150 for 1 molded plastic tile!! What a rip-off!


I don't think you are taking the R&D into consideration.  Properly designed diffusors are not some kind of randomly placed protrusions.  There is a science behind the funny shapes.  If you are serious about making your own, there is a book that can point you in the right direction.  It's a text book with lots of science and math.  

Acoustic Absorbers and Diffusers

You'll have to weigh the time/effort/cost question between finding out how to build your own and doing it vs. going out and paying for pre-manufactured diffursors.
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Frob

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Re: D.I.Y. Diffusers
« Reply #4 on: September 27, 2005, 03:35:18 pm »

the easy est way to DIY it is to buy one and make a mold and then build them from the mold.

eightyeightkeys

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Re: D.I.Y. Diffusers
« Reply #5 on: September 27, 2005, 04:04:35 pm »

If it's a small room then diffusors won't help as much as absorbers. What size of room is it ?
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Dave T.
D&D Music

Norwood

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Re: D.I.Y. Diffusers
« Reply #6 on: September 27, 2005, 04:16:15 pm »

Frob wrote on Tue, 27 September 2005 12:35

the easy est way to DIY it is to buy one and make a mold and then build them from the mold.


Do you work for Behringer?!? Shocked
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Michael Norwood
Wood Bros. Productions

redfro

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Re: D.I.Y. Diffusers
« Reply #7 on: September 27, 2005, 05:27:41 pm »

Norwood wrote on Tue, 27 September 2005 15:16

Frob wrote on Tue, 27 September 2005 12:35

the easy est way to DIY it is to buy one and make a mold and then build them from the mold.


Do you work for Behringer?!? Shocked


LMFBO!!
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Wes Pitzer
WCS Media

Bill Mueller

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Re: D.I.Y. Diffusers
« Reply #8 on: September 27, 2005, 06:51:18 pm »

Rich,

Very simple, very effective and very cheap diffusors are also some of the oldest designs, dating back fifty years or more. I have seen these for years in top recording studios and film houses. They do not look like what you would consider a diffusor however, but when used properly, they work very well at both diffusion and low frequency absorption. A good book to read is F. Alton Everest's book on Building a Recording Studio. Good stuff in there.

Ok, the structures I am talking about are called polycylinders. I have made these things for thirty years. The simplest way to make them is to mount verticle strips of 1"X3"X8' oak, 44" apart, to the wall with heavy duty wall anchors. I like to make a length wise cut in the strips creating a V between the strip and the wall to capture the panel. Then take a 1/8" X4'X8' Oak Luan panel (I like to finish them with Polyurethene) and wedge it between the verticle strips. It will bow out a few inches from the wall and create a nice poly surface. If you make the distance between the strips shorter, the bow will be deeper and it will be a bit harder to get them in, but I find it is better to slightly vary each one so they don't all resonate at the same frequency.

Because they resonate, they also act as a bass trap. You can calculate the exact F0 if you buy the book but I find them to be very effective bass traps no matter what spacing is between the strips. I further recommend that you staple raw fiberglass to the wall in between the strips. It will add absorption and effectiveness to the unit and of course will be invisible after the panels are up.

I usually mount them about 24" up the wall from the floor. This uses up less floor space, does not cover the AC outlets and gives you a convenient place to store your guitar amps. If you ceiling is not 10' then cut them down to 6' height.

If you have a large recording room, stagger them on either side of the parallel walls. You probably don't need them on both walls and they are very effective at breaking up standing waves. In a control room I put one dead center on the back wall with one or two on either side, depending of course on the width of the room. I also like to place them on the rear side walls to create a "live" end of the room. They are great for adding a live component to a Reflection Free Zone design.

They are very easy to take down when you move, and don't permanently damage the wall. They also look stunning and can give a very professional flavor to a room.

For the rest of the room, (front wall and side walls back a foot or two past the listening position) I recommend absorptive panels like Ethans RealTraps.

Hope this is helpful.

Best Regards,

Bill
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Bryson

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Re: D.I.Y. Diffusers
« Reply #9 on: September 28, 2005, 05:21:30 am »

Bill Mueller wrote on Tue, 27 September 2005 15:51

Rich,

Very simple, very effective and very cheap diffusors are also some of the oldest designs, dating back fifty years or more.

More like the Romans were using them.

Here're some poly types that I made.
They have a 4' wide pegboard face curved to a 7.5" max depth, covered with Guilford FR701 fabric. Under the fabric is a layer of poly batting to keep the peg holes from showing on the surface. Behind the pegboard is .5" foam to contain the loosely placed fiberglass batts inside. I have one over the mix position, and one on the wall behind me.

index.php/fa/1629/0/
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rdolmat

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Re: D.I.Y. Diffusers
« Reply #10 on: September 28, 2005, 03:45:01 pm »

Thanks everyone! Always a ton of help here!  Smile

Those poly round diffusers were the ones I was thinking about. I'm not going to try to make the block type with various heights of square pegs.

I'll give those a shot. They seem pretty simple. Yes, I know they probably won't work as well as the uber-expensive ones, but I'm willing to give it a try first.

If they dont work, then pull out the VISA!

thanks again!

cheers
rich
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rich

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micguy

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Re: D.I.Y. Diffusers
« Reply #11 on: September 29, 2005, 04:31:23 pm »

My organic diffusers are literally home-grown - Mother in Law's tongue (a plant that anyone can grow) is a really good natural diffuser - put 'em in the path of reflections you want to kill, and they diffuse them pretty well. Plus they give off oxygen.
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joeq

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Re: D.I.Y. Diffusers
« Reply #12 on: September 29, 2005, 05:10:09 pm »

blairl wrote on Tue, 27 September 2005 12:29



I don't think you are taking the R&D into consideration.  Properly designed diffusors are not some kind of randomly placed protrusions.  There is a science behind the funny shapes.  


Those $150 pieces of plastic are one of my pet peeves.

I can appreciate the R&D and science and the quadratic roots and all that,  but one still has to ask at what point have these R&D costs been amortized?  ("Dammit Johnson!  When are you people in Diffusion going to start showing a profit??")

I have held some of these things in my hand.   Once you have designed such a panel the cost of manufacture has got to be something like two bucks.        

You would think that at least ONE acoustics company would opt for volume sales over high prices and blow everybody else out of the water.

If they were $15 apiece I would buy 10.   The company would take in $120 instead of $148.   Not too bad when you consider that they never get the $148 because I refuse to pay $150 for one lousy diffusor.
 
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BR audio

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Re: D.I.Y. Diffusers
« Reply #13 on: September 30, 2005, 01:45:41 pm »

Hey there,
I'm in the process of building some diffusors for a studio and I have to tell you that it is not as cheap as you think.  Even if the R&D is done for you.  I was doing the math on the QRDs from RPG and they would cost me in parts (wood, paint and stuff) about $350 to $400 each.  That is not including labor.  So I actually started to think that what they are chargin is not as horrendous as I originally thought.  Even though they are producing them in greater quantities.
The problems with home made diffusors such as bamboos, plants, books in big book case and other objects, is the fact that you can't have any accuracy on what frequencies they are affecting.  Not to say that it won't work, but it is just harder if not impossible to taylor them to your room's need.

I saw a repply that mentioned that you also need to consider your room size, and I agree.  If your room is too small (bedroom size), you will be better of worring about absorption.  The biggest problems with smaller rooms are in the low frequency range.  Anywhere below 200hz.  I would recomend taking care of room modes in that area before worrying about diffusion.

If you trying to stay in budget, don't even think about QRDs or Diffractals.  Maybe the polys are your best choice..

my2cents

Very Happy Gil
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Bill B

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Re: D.I.Y. Diffusers
« Reply #14 on: September 30, 2005, 07:48:56 pm »

rdolmat wrote on Tue, 27 September 2005 11:59

Hi all!

Anyone have good tips or suggestions on DIY diffusers?



I built some 'skyline' diffusors using the prime number theory posted on the BBC website. As you build more of these they fit togother to create a bigger diffuser, kind of a fractal thing. Here's a pic: (I hope)
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