Building a QRD diffusor

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mrhotapples

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I'm building one based off a plan I found on the internet that apparently works really well. I want to make sure this isn't a poor design and that perhaps I should find something else.
Here's the directions and some pictures. Looks like it would work!

Diffusor build directions

Now, provided I end up building one, what's the best game plan? I'm in a 20x20 garage, so there's ALL flat surfaces on the walls except for the treatment, amps and instruments. I am mixing in this room a lot, but I check and do mixes in a smaller 10x16 room too. Should I place the diffusor(s) I build symmetrically or only on one wall, say the way the speakers face alongside the first refelction absorption?
 
I just got through building two of these, using the plans off that website as my instructions... I did it slightly different though... I used 2'x2' sheets of 1/4" plywood for the backing board (It is all you need, there's no point in going thicker). In the instructions,it basically says to cut each sheet down to an 18"x18" square before beginning construction. I did not do this, instead I basically just drew some lines on the board so that there was an 18"x18" square in the middle, with 3 extra inches all the way around. The reason I did this is because I'm actually going to build 2 more for a total of four, then use the extra area to put them all together as one piece (48"x48") Once they are all attached as a single piece, I'm going to build a heavy duty frame that goes around the entire assembly, and put the whole thing on legs so they start about 4 feet off the ground, and can be angled by swiveling back and firth to get the best sound diffusion.

For the glue, I used TiteBond II Wood Glue. It comes in a 16 oz. bottle, and when you look at it, you'll think that's enough glue to do two panels, but it's not. It took me just less than 3/4 of a bottle for each panel.

Also, I chose not to hand paint them, as this would have taken way too long. I used Krylon 1318 Dark Gray All-Purpose Primer in a spray can. Each 12 oz. can of primer is about the exact amount you need to solidly cover the entire square, but you must be very careful when doing this, and take your time or else you'll run out of paint, and need an extra can to finish them.

For your question on placement, I can't say for sure as I don't have these installed yet, but all the research I did on these suggests that diffusers do the best job when they are all touching or very close together so they cover a wide area. Now if you wanted to do like a pari of these panels on each wall tht would be ok, but each area you plan to target should have multiple panels right together, or they probably won't do much.

Here's what they cost me to build so far, for two of them.

$2.60 x 2 = 2' x 2' 1/4" plywood pre cut
$1.88 x 14 = 8' length 2x2s
$3.99 x 2 = Krylon 12 oz. Spray Paint Prmier
$5.29 x 2 - Titebond 16 oz. Wood glue

Total is around 55 bucks after tax for a pair of the panels. I'll be posting pics later on once I get everything done, and will probably post a full detailed list of instructions for how I did it.
 
I'm also placing my big 4' x 4' contraption right in the center of my back wall opposite my speakers that way the initial sound will hit these, and scatter hopefully without coming back to my ears. If I need more, I may hit mys side walls at the first reflectio points, but I'll probably have acoustic foam there, so I don' think I'll have any major problems.
 
Great link! building diffusors is my next step once i have the time. i've buit some broadband absorbers (see sig link), and once this term ends i'll have a bit more spare time to build, so i'm going to tackle some diffusors.


Shouldn't be anywhere near as time consuming as building the absorbers (hopefully)!!
 
MessianicDreams said:
Great link! building diffusors is my next step once i have the time. i've buit some broadband absorbers (see sig link), and once this term ends i'll have a bit more spare time to build, so i'm going to tackle some diffusors.


Shouldn't be anywhere near as time consuming as building the absorbers (hopefully)!!
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It looks more time consuming to me... :p
 
89gtsleeper said:
I just got through building two of these, using the plans off that website as my instructions... I did it slightly different though... I used 2'x2' sheets of 1/4" plywood for the backing board (It is all you need, there's no point in going thicker). In the instructions,it basically says to cut each sheet down to an 18"x18" square before beginning construction. I did not do this, instead I basically just drew some lines on the board so that there was an 18"x18" square in the middle, with 3 extra inches all the way around. The reason I did this is because I'm actually going to build 2 more for a total of four, then use the extra area to put them all together as one piece (48"x48") Once they are all attached as a single piece, I'm going to build a heavy duty frame that goes around the entire assembly, and put the whole thing on legs so they start about 4 feet off the ground, and can be angled by swiveling back and firth to get the best sound diffusion.
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Did i miss something, or am i just thick? 18"x18" square, when it's 12 2" studs wide... Shouldn't they be exactly 2'?
 
Yeah, seems to me they're wrong...You need 24 inches. I'm gonna build this on a 2x4 panel of hardboard so I'm just doubling the pattern anyways. No reason to get it confusing.
 
mrhotapples said:
Yeah, seems to me they're wrong...You need 24 inches. I'm gonna build this on a 2x4 panel of hardboard so I'm just doubling the pattern anyways. No reason to get it confusing.
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Wont this make it pretty heavy? I think they suggested 2'x2' to keep the weight down...
 
If theirs way 23 pounds, 46 pounds is not that bad for something that is hardly going to move. My head weighs that much. My amp head, not MY head.
 
mrhotapples said:
If theirs way 23 pounds, 46 pounds is not that bad for something that is hardly going to move. My head weighs that much. My amp head, not MY head.
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lol... i don't work in pounds that often, so don't really know how much that is... Isn't it like 3st 4oz? That's like a 3rd of my weight... :eek:
 
46 pounds is 21 kilograms. I weigh 150 pounds. So it's a third of my weight, but any healthy adult male can lift 46 pounds of weight, especially if it's distributed across 4 feet.
 
mrhotapples said:
46 pounds is 21 kilograms. I weigh 150 pounds. So it's a third of my weight, but any healthy adult male can lift 46 pounds of weight, especially if it's distributed across 4 feet.
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Cool. I don't know about what weight i can lift etc. So when i hear somethings a 3rd of my weight i think it must be pretty heavy, but i suppose it'd not really.
 
Heh, yes. But we're kinda OT. I'm gonna build my 2x4 this week and see what it does for my big flat-walled concrete hole...If it's good, I'll post some helpful tips too! I'm gonna hang it above my absorption on the rear wall's first reflection point.
 
mrhotapples said:
Heh, yes. But we're kinda OT. I'm gonna build my 2x4 this week and see what it does for my big flat-walled concrete hole...If it's good, I'll post some helpful tips too! I'm gonna hang it above my absorption on the rear wall's first reflection point.
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Cool, post some picks if you can :D
 
....

The room is SWEET! I've mixed in it a few times...unreal...
 
Blue Groove said:
The room is SWEET! I've mixed in it a few times...unreal...
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Now that's cool... How'd you get to mix in it? :eek:
 
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