for home made diffuser....

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vegafreak

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Will styrofoam or cardboard egg cartons work better. Anyone know?
 
Neither are diffusive - Both are hazardous.

Egg cartons and Styrofoam only really work in the movies...
 
NL5 said:
Bad, bad, bad idea.......
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really? why?

the lock out studio (for jamm rooms) i go to in Burbank, CA has them hung on the interior walls. i asked the guy what is was (cause it looked like eggcrate foam mattress pads)....

and sure enough.....he confessed it was.

cheap bastard.....
 
Different material, I'm thinkin.

I think all it really does is knock off some highs.

If you've got a small control room......bass traps.
Diffusion may not be needed. And if it is, I'm thinkin not much.

Trap the corners mang....your mixes will come together much easier.

all in my humble opinion, of course. ;)
 
bkkornaker said:
really? why?

the lock out studio (for jamm rooms) i go to in Burbank, CA has them hung on the interior walls. i asked the guy what is was (cause it looked like eggcrate foam mattress pads)....

and sure enough.....he confessed it was.

cheap bastard.....
Click to expand...


That kind of foam doesn't have the density to attenuate sound. Maybe only high freq stuff, but anything lower will go right through it.

If I recall my old physics, the actual mechanism that attenuates sound is when the energy passes from one medium to another. A little bit will be absorbed, a little bit reflected, and a lot converted to heat as it moves the medium. The greater the difference in densities of the mediums, the greater the attenuation. The more mediums the sound has to pass through the greater the attentuation.

The acoustic foam is closed cell, the material is more dense and there is many more air pockets than that mattress foam. Foam is basically made up of plastic with lots of air pockets. Sound traverses through both... plastic - air- plastic - air - plastic, etc. So when sound energy passes through, more energy is dissipated because it takes more energy to move the material (converting to heat) and it occurs many more times as it passes through the air pockets.

I'm guessing that rigid fiberglass boards work well because the fibers are so closely woven together that air movement is restricted, plus they are so thick there are a lot of medium interfaces that the sound passes through. Fiber-air-fiber-air-fiber-air, etc.

Hmmm, not so easy to explain in a post.
 
Chili said:
If I recall my old physics, the actual mechanism that attenuates sound is when the energy passes from one medium to another. A little bit will be absorbed, a little bit reflected, and a lot converted to heat as it moves the medium. The greater the difference in densities of the mediums, the greater the attenuation. The more mediums the sound has to pass through the greater the attentuation.
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You remember the physics fairly well, but if my memory serves half as well, you are kinda throwing two parts absorption and one part diffusion into one pot there.

Now, the name of this thread deals with diffusion. Whether this is because vegafreak actually means diffusion or whether he's actually looking for absorption, I don't know. But strictly speaking, diffusion does not require any absorption (though there usually is at least some, whether incidental or intentional). The main purpose for diffusion panels is to break up directional reflections - i.e. to diffuse the sound in the room rather than reflecting it like laser beams in a mirror. (Also, by definition, this is intended only for those higher frequencies prone to such direct reflection issues.)

This is why diffusion panels tend to come in a few popular designs. One is a randomly irregular surface, not the pyramids of absorber panels which are designed to trap sound, but rather something like a chessboard with each square sticking out a different distance. The ireregular surface means the sound hits each block at a slightly different angle, and therefore reflects back at a slightly different angle than it's neighbor. This diffuses the sound in the room. These can be easily made by buying yourself a 2x2, cutting it into many irregular lengths from 1" to a few inches and then gluing them together in a checkerboard pattern with some carpenter's glue.

Another is a simple convex curved surface bowed in towards the room. Sound hitting each point on the curve will be reflected at a slightly different angle. Also fairly easily made by buying a 2'x4' sheet of hardwood (not plywood), steam/soaking it until it's pliable and bending it into a curve around a shaped 2x4 cut into the desired a curve shape. Clamp into place and let dry.

Note the the wood ones will be almost pure diffusers, not a lot of absorption going on. If you want some absorption as well, they can be made of more porous and energy absorbing material. But absorption is not always a wonderful idea. We have all talked about the curses of an overly-dead room. If you want to keep some liveliness without the problems of slapback, comb filtering and other first-reflection problems, a pure diffuser is just the ticket.

G.
 
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SouthSIDE Glen said:
These can be easily made by buying yourself a 2x2, cutting it into many irregular lengths from 1" to a few inches and then gluing them together in a checkerboard pattern with some carpenter's glue.
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Not to poo poo on a pretty good post, but I was under the impression that it was WAY more complex than that. I thought there was some kinda crazy algorithm that determined the length of each block. Or am I mis-remembering?
 
SouthSIDE Glen said:
You remember the physics fairly well, but if my memory serves half as well, you are kinda throwing two parts absorption and one part diffusion into one pot there.

G.
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Thanks G. Nah, I wasn't referring to diffusion at all. I know it's totally different from absorption. I was replying to bkkornaker's post about the mattress foam and why it's not a good candidate from sound absorption. Then I just threw out useless information on why some stuff works and others don't. Essentially, hijacking the thread. :o

Cheers,
 
NL5 said:
Not to poo poo on a pretty good post, but I was under the impression that it was WAY more complex than that. I thought there was some kinda crazy algorithm that determined the length of each block. Or am I mis-remembering?
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Good point. I'm sure that there's math to ensure a high degree of randomness; i.e. that if you have a block of length x and a block of length y, you don't want to have them spread z inches apart because they will just wind up reflecting back at the same angle, and stuff like that. Also the size of the squares themselves may play a part in bandwidh limiting the effectiveness of the diffusion, I would guess. I'm sure such math could be found on the Internet.

Personally, I find that a bookshelf or bookcase tends to do the job fairly well too ;).
Chili said:
Thanks G. Nah, I wasn't referring to diffusion at all. I know it's totally different from absorption. I was replying to bkkornaker's post about the mattress foam and why it's not a good candidate from sound absorption. Then I just threw out useless information on why some stuff works and others don't. Essentially, hijacking the thread. :o
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My fault for not reading the whole tread from the beginning, Chili. Sorry 'bout that. Not that I was criticizing to begin with or anything, I didn't mean to single you out.

:)

G.
 
Dogbreath said:
No Hijacking. :cool:

I'll report you to a mod.



:D
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And you know what's funny is I don't get notifications for reported threads. MSHilarious got them for one day. So, go ahead, report me. But, really, we told France and hopefully they'll get it fixed soon.

SouthSIDE Glen said:
I didn't mean to single you out.

:)

G.
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I know.... :D

NL5 said:
Not to poo poo on a pretty good post, but I was under the impression that it was WAY more complex than that. I thought there was some kinda crazy algorithm that determined the length of each block. Or am I mis-remembering?
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Yeah, i remember seeing a matrix posted somewhere, but I couldn't find it. You're right, it's not random.

Bringing this back to the original post (so I'm not hijacking anymore), I don't think the OP needs diffusion. Based on his other threads, he's got a small room and according to Ethan, absorption is the best method tuning the room. Do I have that right?

Cheers,
 
Chili said:
Bringing this back to the original post (so I'm not hijacking anymore), I don't think the OP needs diffusion. Based on his other threads, he's got a small room and according to Ethan, absorption is the best method tuning the room. Do I have that right?
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I think the short answer is, "It depends...." ;)

Absorption in terms of bass trapping, sure. And if a room winds up being extremely bright like a walk-in plate chamber, then sure some percentage of HF absorption/deadening will probably help. But one usually doesn't want overly dead rooms, either. I've never seen or heard of an engineer or acoustic designer actually advocating working within an anechoic chamber for anything but laboratory testing. IMHO, the goal is to eliminate *problems* (such as bass modality, comb filtering, standing waves and such) without creating such an artificial-sounding space as to sound unnatural to the ears. Some degree of ambiance is desirable. Hence the difference between using absorption and diffusion in certain situations.

G.
 
Title= "for home made diffuser...."

so what are we talking about here? diffusion? or absorption?

and what the heck is the difference (if any)?
 
bkkornaker said:
Title= "for home made diffuser...."

so what are we talking about here? diffusion? or absorption?

and what the heck is the difference (if any)?
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Go back and re-read the last few posts, it's all pretty much spelled out. But in short, absorption stops sound from reflecting by absorbing it's energy, diffusion doesn't stop reflection but it diffuses the reflected energy in many different directions, rendering it fairly harmless without absolutely getting rid of it. Absorption deadens sound, diffusion de-focuses it.

G.
 
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