DIY quadratic diffuser

Thanks for your reply -- I'm a babe in the woods when it comes to woodworking... ;)

Why use 2x4s as the base? I'm thinking that using 2x2s would mean all I had to do is cut to length.

I think the numbers in the BBC report are "well depth" which you have to flip to get "block length". I.E., zero is the highest, and 4 means no block at all.

If I'm reading/figuring this out right, I need blocks that are 2", 4", 6" and 8" long -- all 2x2 lumber.

After I cut it, do I need to sand the end for good glue adhesion?

What kind of glue should I use?

One big problem is that there are some cells that don't have ANY block in them - so you can't clamp the blocks down.

Thanks!
-lee-
 
Lets go back to the design with the 2 1/4 gutter drain. Could you use sticky vinyl flooring tile to attach to the end of the tubes. Also this would act like a mini wide band panel absorber for lower freqencies.

The frequencies absorbed would depend on the depth of each tube and the density of the flooring tile if there is enough room for the tile to resonate. It should still be able to diffuse the higher frequencies that it is designed for and you get a little low-mid absorption for free!!!!!

Do you think this would happen? In theory it should.

Eric
 
Also to those who are thinking about wood, draw a grid on your backer board and write down the number right on the wood and then group the pieces that you cut and write the corresponding number on on the group after you've cut the length. This should make piecing together much easier.

Eric
 
Ahhh!! you are trying to build a block diffuser as in the BBC design...I thought you were trying to build the other type with varying well depths which is why I was going with what C7sus said about using gutters which are open on one side. If you were to get maybe 4 - 5 different sizes and lay each next to the other and stuck it on the wall - presto a cheap diffuser.

I've seen lots of those block diffusers. Basically they get a 8 x 4 sheet of MDF. Then they go to a construction site and get all the 2" x 4" lumber offcuts of different lengths and glue them vertically onto the MDF. Spray paint and hang on wall. :)

cheers
john
 
Hold on there, Mr. Sayers! ;)

Are you telling me all my agonizing over the cell size and length of each cell is going too far, and I can get reasonable diffusion with a pile of 2x4s of different lengths over a big area on my wall?

In other words -- in the *real world* (as opposed to mathematical nirvana), do the lengths and face size not matter as much as the pure ideal case math would indicate?

About how long is the range of 2x4 lengths that you've seen?

Thanks much,
-lee-
 
just built a quadratic diffuser tonight with all 1/2" maple plywood.
this thing is outrageously heavy. i uses almost 2 full 8'x4' sheets. it took me about 2 hrs to cut, glue and pin everything. dont know if i could stand to build 20 of these things. the overall dimensions are 24 in wide, 48 tall, and 9 inches deep.



lynn
 
Forever rain...can you post pictures??

Laptoppop - THe reason I said 2 x 4 studs is because they are cheap and easy to get un-pressure treated. Also some of the cells could be a be a solid piece turned on its side rather than cutting hundreds of little 1.75" blocks. This would save on gluing and improve structural integrity. I said sand them because it would look better and generally does help glue stick better. By the way, if you get the wood on the perimeter done first, then you can glue to it as well as the bottom to make a more solid structure.

Definately use wood glue. You can get it for cheap at Lowes or Home Depot or maybe Walmart.

Does a babe in the woods mean you are good at wood working or bad at it??

Beezoboy
 
i will, as soon as i find my digital camera. it basically looks like the attached file, except it is 48" tall instead of 24", and i used the multiples of the number 11. so it is 9" deep.
 

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Beezoboy said:
Does a babe in the woods mean you are good at wood working or bad at it??
Click to expand...

It means I have virtually no experience with wood working or what works or doesn't.

Can you use wood glue without clamping the pieces together?

Thanks,
-lee-
 
This is a studio in Brisbane where I recorded an album a few years ago. They have every type of absorber on different walls. Panel absorbers, slots and block type diffusion.

studio2wci.jpg



I though you were trying to build cheaply what Lynn has just built but using gutters or similar instead. :)

cheers
john
 
Jeez, John, good thing we can do pictures - I, on the other hand, thought pop was building a pipe organ :=)
 
this is the plan i have developed for my parts. we have a cnc router here at work, so that will run all my notches. the one i built last night did not have any notches and it was a real pain in the arse to build. hopefully this one will be a little easier. i will let you all know how it turns out. if anyone wants the autocad drawing of this, let me know.




lynn
www.therecordinghouse.com
 

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One of the guys that posts over on RO, JeffZ, was looking into that (patent office) and he said at one time that it looked like the patent had expired - I have a hard time believing that RPG would have let that happen, so I'd look VERRRRY carefully at patent records before doing anything commercially.

And, yeah, you can build them for yourself - no more dangerous than tearing off those "do not remove" labels on your seat cushions/mattresses... :=)
 
just wondering if the cavities in the rear would benifit from being stuffed with insulation or anything. seems there would be quite a bit of reasonance happening back there.




lynn
 
surely patenting a diffuser design is like trying to patent a helmholtz resonator design - as I said before there are plans and designs for diffusers going back to the eighties through the BBC site. Well before RPG was around.

cheers
john
 
foreverain4 said:
just wondering if the cavities in the rear would benifit from being stuffed with insulation or anything. seems there would be quite a bit of reasonance happening back there.




lynn
Click to expand...




wouldnt the reasonance cause spikes in their prospective frequencies?
 
John Sayers said:
This is a studio in Brisbane where I recorded an album a few years ago. They have every type of absorber on different walls. Panel absorbers, slots and block type diffusion.
Click to expand...

wow, that's a wild looking room and a lesson in acoustic treatment. How did it sound in there John?
 
Dan - the studio sounded very good. It was the control room I had a problem with as it was one of those all diffusion/no absorption type control rooms and I found it hard to mix in there.

cheers
JOhn
 
foreverain4 said:
just wondering if the cavities in the rear would benifit from being stuffed with insulation or anything. seems there would be quite a bit of reasonance happening back there.
Click to expand...

I would agree -- except for one thing -- didn't you mention that you are building this beast out of 1/2" maple plywood? That would seem to me to be so heavy and thick that high frequency resonances from little chambers wouldn't be an issue.

On the other hand, if it makes you feel better, stuff the cavities full with whatever you have handy. Insulation or even old t-shirts! ;)

-lee-
 
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