first diy diffuser build. QRD and 2D skyline types for Magnepan system.

Rclark · « **Reply #40 on:** 21 Apr 2013, 12:53 am »

I think Gik's are also eps, and when I asked about them was told they were useful to 300 hz. Has to do with the depths of the wells, not the material, right.

That big 4•8 also goes pretty low says the guy from SRS.

Rclark · « **Reply #41 on:** 21 Apr 2013, 04:59 am »

I think with my crude understanding of things so far, I decided I'm not going to build a modular 4*8 that can seperate into three, I'm just going to build 2 seperate, 4' * 4' diffusers and put one each behind a speaker.

Nothing stopping me but the time to do it. So yeah, Wed is when I start on this.

medium jim · « **Reply #42 on:** 21 Apr 2013, 05:17 am »

Quote from: rodge827 on 21 Apr 2013, 12:24 am

No I don't know him.

He has worked with Bonnie Raitt, Fleetwood Mac, to name a few, as well as a solo artist and has done some studio work in Nashville....maybe not as much as Brent Mason or Johnny Hiland. He moved his family from Los Angeles after the big Earthquake in 1994....

Thanks for getting back on the question,

Jim

Alex Reynolds · « **Reply #43 on:** 21 Apr 2013, 05:33 am »

Quote from: Rclark on 21 Apr 2013, 12:53 am

I think Gik's are also eps, and when I asked about them was told they were useful to 300 hz. Has to do with the depths of the wells, not the material, right.

We have EPS diffusors and we have wood diffusors. However, none of them diffuse down to 300 Hz, and certainly not the GridFusors. The wooden Q7ds scatter down to 400 Hz or so I believe, but the GridFusors won't go much below about 800 Hz if memory serves me correct. The problem is most other companies list the scattering coefficients as the upper and lower limit of the diffusors instead of the actual useful diffusion coefficient. So in order to compete we list both, but we do at least distinguish that 350 Hz is not the actual lower diffusion coefficient. Diffusors would need to be well over one foot deep and you would need to be incredibly far from them to get real diffusion at 300 Hz.

Rclark · « **Reply #44 on:** 21 Apr 2013, 06:36 am »

Well the gridfusors are very shallow and I don't think anyone would expect them to diffuse very low. but your QRD diffuser, the eps one, I inquired about that one and was told it would diffuse down to 3-500 hz.

Either way, no big. I would still consider successful diffusion to 700 hz quite an accomplishment. I'm going for 7" depth and so should be good and into 500hz at least.

Rclark · « **Reply #45 on:** 22 Apr 2013, 03:53 am »

Well I ended up having the time to get these early. I can just spend Wed cutting. Anyway, it's a VERY large stack of foam, and these diffusers are going to be quite a bit larger than I was thinking.

Hopefully I've just turned my small room into an auditorium.

Well, time to download a calculator and read, plan this out. Definitely out of my element here. Wish me luck.

tabrink · « **Reply #46 on:** 22 Apr 2013, 04:06 am »

Rclark,
I used 4 2" layers (4'x8') and used DSA 20 adhesive between them (not going anywhere) and covered with wife pleasing Khaki fabric with a similar set up in all three of our homes!
Only took a wee bit of tweaking with the exception of the lake home. Ended up only applying to rear walls on the 1.6. May have been due to area rugs over quarry tile for wet feet!
Best,
Tom

SteveRB · « **Reply #47 on:** 22 Apr 2013, 04:02 pm »

good luck,

keep the photos coming. I may go down the same route vary soon.

Rclark · « **Reply #48 on:** 22 Apr 2013, 05:55 pm »

Thanks.

I have about 5 different pages/sites open, reading the finer points on this stuff. There's quite a lot to consider. The QRDude software looks to be very robust though. If I'm successful with it, then I'll make some smaller 2D types for my front wall.

Pretty excited. These QRD's are going to completely dominate the back wall. Which is what I was after I guess.

I suppose I should rename this thread.

Maritan · « **Reply #49 on:** 22 Apr 2013, 06:36 pm »

Wait. The QRDs are going on your back wall? The wall behind you? And then you might make 2D diffusers for the front wall (the wall behind the speakers)?

I must have missed your reasoning for this. I'll have to go back and look through the thread.

In any case, good luck.

Projects like this can be so rewarding.

Rclark · « **Reply #50 on:** 22 Apr 2013, 06:43 pm »

thanks

think like these, only uglier:

I'll be looking at them, past my speakers, on the back wall.

Thinking small 2D diffusers for the wall I'm on, up above my listening position.

Rclark · « **Reply #51 on:** 22 Apr 2013, 09:35 pm »

Well nothing to it but to do it. Going to take me a few days, I only have 4 clamps.

First off comes the foil backing

Oh look, the front label comes off too. Who knew.

So using contact cement. The hot knife suggestion, well nobody has one I can just go pick up, not for less than $100. This adjustable, fine toothed saw seems to go through the foam like butter, and I can adjust the blade to make accurate cuts to depth. I guess some sandpaper will take it from there..

First panel clamped up, CD placed to show the size. So far so good!

Alex Reynolds · « **Reply #52 on:** 23 Apr 2013, 05:34 am »

Quote from: Rclark on 21 Apr 2013, 06:36 am

Either way, no big. I would still consider successful diffusion to 700 hz quite an accomplishment. I'm going for 7" depth and so should be good and into 500hz at least.

Yes, absolutely.

TRADERXFAN · « **Reply #53 on:** 23 Apr 2013, 06:11 pm »

I don't understand why they are being glued face to face in full sheets... please elaborate on what you are going to do to make this?
Thought would have been cut to length before glue-ing.

-Tony

Rclark · « **Reply #54 on:** 23 Apr 2013, 11:56 pm »

Because I'm just going to cut into the face of these, rather than slice them into pieces and glue them to something.

Lots of reading yet to do, and fiddling with QRdude, which looks like a very nice piece of software. Surprised it's free.

But I feel confident that I'll be able to cut finely and make some good higher freq diffusion too. I'll just go slow.

TRADERXFAN · « **Reply #55 on:** 24 Apr 2013, 05:49 am »

Sorry. I still don't think I understand what you are going to do.

You are going to cut cavities into the what is now "block" of 4 layers of foam?
If so, with what? And why this way instead of something like PDR showed for his process?

Just curious.

Rclark · « **Reply #56 on:** 24 Apr 2013, 06:07 am »

Quote from: TRADERXFAN on 24 Apr 2013, 05:49 am

Sorry. I still don't think I understand what you are going to do.

You are going to cut cavities into the what is now "block" of 4 layers of foam?
If so, with what? And why this way instead of something like PDR showed for his process?

Just curious.

I'm pretty much shooting in the dark. This is all experimental.

PDR has a fabulous looking diffuser, and it's a one piece. What I was hoping to do was make this diffuser with very thin walls so I can have a lot of wells, and diffuse to a low range but also up higher, but also be modular so that it can be seperated.

jk@home · « **Reply #57 on:** 24 Apr 2013, 12:53 pm »

There's some info on diy foam diffusers here:

http://www.avsforum.com/t/1312919/diy-sound-diffusers

Also this is a good source:

http://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/

Rclark · « **Reply #58 on:** 24 Apr 2013, 05:20 pm »

Well, let me ask, does anyone think my approach at construction is a mistake? I've only glued four panels and can always go buy 4 more. They're cheap.

What's wrong with cutting into a stack? I'm not seeing the problem. It will still be a 4*8 diffuser.

PDR · « **Reply #59 on:** 24 Apr 2013, 06:07 pm »

Rclarck, have you decided what your going to use yet as far as well
width?
The picture above is the one I made, I chose 1 1/2" wide wells so
I used 1 1/2" sheets. You can see I have them all numbered on the ends.
If you are going to try and cut them out of a solid block, I would try it
before gluing any more together, especially if your going with narrow wells.
This stuff cuts very well on a table saw....but I'm curious to see what you have in mind.