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post #1 of 381 Old 02-04-2011, 05:04 PM - Thread Starter
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A couple weeks ago I was telling a friend about how I might have to package and ship some large items. He said he knew a guy that might be able to help and gave me his business name and contact info.

It turns out the guy deals with making specific styrofoam shapes for packaging. I haven't contacted him yet, but I just thought about something today. What if I could ask him to make a specific shape for sound diffusers? I know people use styrofoam to make them anyway.

Something 'similar' to this:




That shape has a patent I'm sure, but it's just the actual shape that has the patent, not the styrofoam or the fact that it's a diffuser. There are plenty of similar diffusers on the market, but they're all very expensive for what they are.


Anyone interested in figuring out another design? I can contact the company next week and see what they say. Maybe we could get some inexpensive diffusers made up......and not $300 a piece.
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post #2 of 381 Old 02-04-2011, 05:46 PM
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Quote:
Originally Posted by Erich H View Post

Anyone interested in figuring out another design? I can contact the company next week and see what they say.

Try this program out.
http://www.subwoofer-builder.com/qrdude.htm

Here is a very good primer on the subject.
http://www.subwoofer-builder.com/qrd.htm
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post #3 of 381 Old 02-04-2011, 07:17 PM - Thread Starter
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Thanks Soho54, that's some pretty good reading. I don't grasp the whole concept just yet, but I'll go back over it a few more times.

After reading it, I wonder what they could actually patent in the one I posted above. Seems like a fairly open plan to use. I've seen a lot of other designs that don't use the same square/rectangle structures but seem to get decent reviews.

I found this site talking about a few different repetitive designs:

http://www.sae.edu/reference_materia.../Diffusion.htm
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post #4 of 381 Old 02-04-2011, 08:44 PM
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I'd be interested in some QRDs. I'd probably prefer the 1D diffusors and those are probably easier to make. Maybe he could build regular and inverse panels so each sheet could produce two diffusors and would then be placed back together for shipping. Maybe N17 2ft x 2ft x 4in panels. I think that gives diffusion where it is best used from 1600-6800 without becoming too thick.

I'd be in for a bunch of those if the price was low. They could even look ugly and rough because I'd probably encase them in frames and cover with speaker cloth.
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post #5 of 381 Old 02-04-2011, 09:00 PM
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Wow this is funny, I just was talking to a good friend of mine that's visiting for the weekend and he brought up trying to build some of these. He mentioned that they're usually built out of 2x2's instead of foam though as they're supposed to reflect and not absorb... We were trying to come up with a reasonable size using one of the online calculators that was a good balance between depth and frequency range.

Does anyone know what range is generally targeted by these? We were looking at making three of the with a depth of about 4.5". The range would be 1.5kHz to 3.3kHz and would be about $10 a piece to make.

We were using this calculator:
http://web.archive.org/web/200704292...alculator.html

Edit: oops, just read the rest of the post above this one... I'll have to look into that specific frequency range
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post #6 of 381 Old 02-04-2011, 09:16 PM - Thread Starter
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Quote:
Originally Posted by lennon_68 View Post

He mentioned that they're usually built out of 2x2's instead of foam though as they're supposed to reflect and not absorb...

Lennon, the harder styrofoam would reflect, not absorb.


Also, in the link I posted above, the guy says:

"they can be built as low frequency absorbers yet will also act as diffusers"

That would be pretty nice. But maybe not the best way to go, I'm not sure.



If the styrofoam was smooth enough, they could easily be painted with latex paint. There are some really neat looking rooms with other diffuser designs, but I'm a bit ignorant right now on what the best "all around" design might be, but I'll keep reading.
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post #7 of 381 Old 02-04-2011, 09:24 PM - Thread Starter
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There must be different ideas going on here because some say you need an odd number of spaces, certain depths, and spaced out a certain amount, etc. Then there are others that are simply curved boards or a mismatched bunch of raised angles, and some that just have an exact repeating pattern like a foam absorber with no change in the initial pattern.

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post #8 of 381 Old 02-04-2011, 11:42 PM
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Erich,

Have you seen this information? http://www.pmerecords.com/Diffusor.cfm

This looks like public information for DIY a 2D QRD type diffusor, is this what you are looking for?

Mike
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post #9 of 381 Old 02-05-2011, 12:13 AM - Thread Starter
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Thanks for the link. There's some pretty good information out there for these, and the more I read, the better they sound.

I don't see why these couldn't be produced in larger quantities for some DIY guys. They just have to look really nice.

But as mentioned, I haven't talked to the packaging guy yet, so I'm not sure if this is something he would do for a good price or not.
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post #10 of 381 Old 02-05-2011, 07:04 AM
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From what I've gathered the mathematical diffusers are the most predictably effective. For a DIYer it is obviously difficult to be nearly as precise as a pro with their extensive budgets and measurement and analysis tools. By having diffusers that we can have an idea of their effect we can better implement them.

I'd like to stick to QRDs, either 1D or 2D. There are other math diffusers but they aren't as common or well documented in their implementation thus making it more difficult for us. I suggest 1D because it is probably easiest to implement since cutting could occur on a single axis. If 2D is feasible it is supposedly superior so I'd be all for that instead.

Styrofoam, unless it is somehow exceptionally open cell, won't act as an absorber beyond the absorption that normally occurs with a diffuser regardless of material. It is perfectly fine material for this.

Like I said before, I'd be fine with a rough finish because I would like encase them in grille fabric similar to an absorber panel. Short of the nicer looking wooden diffusers that could be stained, I don't care for the exposed diffuser look. I also think it is important to stick to a reasonable form factor. Somewhere around 3-5" deep and 2ft x 2ft sounds good to me.
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post #11 of 381 Old 02-05-2011, 07:44 AM
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I would buy some!!

My HT room only has 2" OC703 treatments, I have always wanted to explore the ideas of diffusers.

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post #12 of 381 Old 02-05-2011, 08:30 AM
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Thanks for the input guys. It looks like it may be cheaper (and lighter... and less work...) to build one out of that foamboard stuff that Home Depot sells then? Playing with the calculator above if I move the upper end range to 6.8kHz it says to use 1" x 1" pieces of material but that results in just a 1sqft panel. Does that sound right or am I looking at something wrong? Actually playing around with it looks like the 6.8kHz was recommended as it uses 1" columns and my buddy was using 3.3kHz as that was the sweet spot for using 2x2's...
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post #13 of 381 Old 02-05-2011, 08:43 AM
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Quote:
Originally Posted by Erich H View Post

If the styrofoam was smooth enough, they could easily be painted with latex paint.

Erich,

Wouldn't painting them take away from the absorption?


EDIT: Just re-read the link and I guess you were looking more for the reflective properties?.?.?

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post #14 of 381 Old 02-05-2011, 09:50 AM
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Quote:
Originally Posted by Erich H View Post

There must be different ideas going on here because some say you need an odd number of spaces, certain depths, and spaced out a certain amount, etc. Then there are others that are simply curved boards or a mismatched bunch of raised angles, and some that just have an exact repeating pattern like a foam absorber with no change in the initial pattern.


One comment on the repetitive structures shown as diffusors. Bad idea. A single half-round acts as a diffusor. A series of half rounds forms a periodic structure that interacts with itself, reducing diffusion. Toole talks about it in his book, and pictures of the Harman test room only show one half-round, roughly mid side wall.

The wooden block and rock wall diffusors won't have the bandwidth of the isolated half round, but being random, they don't interact if placed close to one another.

Something to consider...
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post #15 of 381 Old 02-05-2011, 10:02 AM
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Yes, the half rounds are not a good idea unless they conform to some math diffusion model. You can use half rounds for a QRD but it is generally harder to build. It extends the effective frequency range higher.

There is a reason most commercial diffusers are either 1D or 2D QRDs or an enhancement of that basic design. They work. Plus, we can predict how they will work and how we can use them in rooms to have a positive effect. I would only be interested in a relatively plain 1D or 2D QRD that can be effectively model beforehand.
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post #16 of 381 Old 02-05-2011, 10:08 AM - Thread Starter
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Quote:
Originally Posted by dbldare View Post

Erich,

Wouldn't painting them take away from the absorption?


EDIT: Just re-read the link and I guess you were looking more for the reflective properties?.?.?

dbl

Yeh, these wouldn't be intended to absorb, but just the opposite. I read a lot last night and I think the 2D style using blocks is the best way to go.

The deeper they are, the lower the frequency they can handle. But they don't have to be extremely deep to work well.

We need to figure out an AVS Diffuser System.
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post #17 of 381 Old 02-05-2011, 10:42 AM
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Skywalker sound studios went DIY with theirs:

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post #18 of 381 Old 02-05-2011, 01:02 PM
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QRD's are on my project list.

I think they could have a cool artsy look w/the right kind of paint.

A couple that I saw are a stony pebbly look and a faux copper/bronze.

The youtube almost got to describing the principle; the key point that was missed is that the different depths delay the reflections different amounts and the phase differences steer the wavefronts in different directions.

Noah
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post #19 of 381 Old 02-06-2011, 12:30 PM
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Yup, I made mine with styrofoam. I have a nice layout that I can send anyone if they want it. The lenths are random from less than an inch to 7" deep. They scatter sound quite well. I can make a panel 48"x48" for less than 40.00....... The cost of a sheet of 2" thick styrofoam 4'x8'. Only thing you will need to purchase online is a styrofoam cutter. I had to make extensions to get more depth out of the cutter, but that was easy. The cutters are about 35.00 online, but that was a while ago. I also bought a real cheap spray gun and gave them a dose of gray paint the color of my room. Perfect they are not, but close enough for me....

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post #20 of 381 Old 02-06-2011, 01:22 PM
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Quote:
Originally Posted by kgveteran View Post

Yup, I made mine with styrofoam. I have a nice layout that I can send anyone if they want it. The lenths are random from less than an inch to 7" deep. They scatter sound quite well. I can make a panel 48"x48" for less than 40.00....... The cost of a sheet of 2" thick styrofoam 4'x8'. Only thing you will need to purchase online is a styrofoam cutter. I had to make extensions to get more depth out of the cutter, but that was easy. The cutters are about 35.00 online, but that was a while ago. I also bought a real cheap spray gun and gave them a dose of gray paint the color of my room. Perfect they are not, but close enough for me....

http://i198.photobucket.com/albums/a...n1/smside2.jpg


We built three 18"x18" using 2x2's (actually 1.5" x 1.5") today. They are quite heavy though. Waiting for the glue to dry then we're going to play with placement options. For using styrofoam I was thinking of just cutting it with a table saw, any reason not to do so?
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post #21 of 381 Old 02-06-2011, 01:34 PM
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Pshhhhh. Those diffusers are fine, but I like mine more:



I've got them smack in the middle of the wall behind my seating position. Not too sure if they actually help or not, but I certainly enjoy the...ahem...benefits.
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post #22 of 381 Old 02-06-2011, 01:38 PM
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Edit: let me expand a little..

Quote:
Originally Posted by lennon_68 View Post

For using styrofoam I was thinking of just cutting it with a table saw, any reason not to do so?

If it isn't too thick just use a straight edge to score it with a razor knife, and then snap it.

If it is really think you can use a table saw. If it if pretty dense any blade will do. If if is the more brittle type turn the blade around backwards for a smooth edge.
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post #23 of 381 Old 02-06-2011, 02:24 PM
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Quote:
Originally Posted by soho54 View Post

Edit: let me expand a little..

If it isn't too thick just use a straight edge to score it with a razor knife, and then snap it.

If it is really think you can use a table saw. If it if pretty dense any blade will do. If if is the more brittle type turn the blade around backwards for a smooth edge.

Thanks for the tips
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Quote:
Originally Posted by soho54 View Post

Edit: let me expand a little..

If it isn't too thick just use a straight edge to score it with a razor knife, and then snap it.

If it is really think you can use a table saw. If it if pretty dense any blade will do. If if is the more brittle type turn the blade around backwards for a smooth edge.

If cutting with a table saw, be prepared for a mess to clean up. The particles of star-foam will cling to everything.
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post #25 of 381 Old 02-06-2011, 02:36 PM
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No sawing as the foam will stick to everything and make quite a mess. The styrofoam cutter is powered and cuts through with no dust with a thin special wire that can handle the voltage...
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post #26 of 381 Old 02-06-2011, 02:59 PM
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It just depends on the type of foam, and your table saw set up. A scatter shield will solve most problems.

Well, MDF clean up still sucks. That crap gets everywhere.
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post #28 of 381 Old 02-06-2011, 03:28 PM
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Quote:
Originally Posted by Starkiller4299
Pshhhhh. Those diffusers are fine, but I like mine more:

I've got them smack in the middle of the wall behind my seating position. Not too sure if they actually help or not, but I certainly enjoy the...ahem...benefits.
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post #29 of 381 Old 02-06-2011, 03:36 PM
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I'd think the more dense foam that sign makers use would be good.

I saw an episode of "How It's Made" where they were carving it with a CNC router and it cut really clean. If you could get the 2" thick material slit into 2x2 strips by the distributor, it would be easy to cut to length on the miter saw.

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post #30 of 381 Old 02-06-2011, 03:45 PM - Thread Starter
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Quote:
Originally Posted by petew View Post
I'd think the more dense foam that sign makers use would be good.

I saw an episode of "How It's Made" where they were carving it with a CNC router and it cut really clean. If you could get the 2" thick material slit into 2x2 strips by the distributor, it would be easy to cut to length on the miter saw.
That stuff is heavy. Plus it's very expensive for what it actually is.
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