Patches of Absorbent

Julián Fernández · Post by **Julián Fernández** » Tue Apr 26, 2005 3:25 am

Steve... this is something you told me some time ago...
Can you give me some details about it... by now i won´t angle my walls on the recording room (4 x 3 x 2,4 mts), so, i would like to know a little more about this method... ThanKs!

"...Parallel walls should have patches of absorbent alternating on opposite walls (so the patches are not directly across from each other) - these should be anywhere from 2x2 foot to the full size of a batt (2x4 foot) and 3 or 4 inches thick; spacing them away from the wall a few inches will also help in the low mid frequency range.

This (alternating wass/absorber) will treat flutter between the parallel walls, and tame the brightness a bit; it will also help some of the "boxiness" of the room from too much mid frequency. If this isn't plain, ask and I'll explain further..."

knightfly · Post by **knightfly** » Tue Apr 26, 2005 9:46 am

Which part isn't clear? Steve

Julián Fernández · Post by **Julián Fernández** » Tue Apr 26, 2005 1:00 pm

So, it´s just 2x2 panels of rigid fiberglass alternating on opposite walls?
Should i put them all over the 2 walls, or just a few of them?
Which is the best way to space them from the wall?
Something like this?

cadesignr · Post by **cadesignr** » Tue Apr 26, 2005 1:53 pm

You could use "Diamond Theory" as a basis for geometric tiling. There are literaly billions of combinations. Just a thought for graphics using Fabric covered absorption materials. Among others. Here is an illustration. This all has to do with the "edge effect" of absorbers too.

If you are interested:
http://m759.freeservers.com/puzzle.html
http://m759.freeservers.com/

There are tons of links from this last page. Tiling is a fasinating subject
fitZ

Julián Fernández · Post by **Julián Fernández** » Thu Apr 28, 2005 12:09 pm

Thanks cadesignr! Interesting stuff... and how about construction of the patches? Just rigif fiberglass spaced from wall with wood?

cadesignr · Post by **cadesignr** » Thu Apr 28, 2005 2:35 pm

Hello Julián. Usually rigid fiberglass comes in 24" x 48 " panels. Cut them in half for 24" x 24" squares. Then cut diagonally corner to corner. That will give you 4 diamonds per panel. The blank diamonds are simply the wall, or what ever. Even 703 wrapped with a different color fabric. There are many ways to do this. If it were me, I would cut 1/4" plywood or MDF diamonds to match. Then nail 1x 1" cleats along the edge of the ply diamonds. This would space the fiberglass out for lower frequency absorption. Then wrap the panels with fabric, stapling the fabric to the back of the ply. Then staple wide velcro strips on 3 corners.

The key here is to get your pattern down first. One of those links shows many patterns, but there are litterally billions. As you can see. That is the point of diamond theory. Anyway, once you have a pattern, then lay it out maybe full scale on a wall with pencil. Everywhere there is a fiberglass diamond, fasten another 1/4" ply diamond to the wall. Only these diamonds, cut 1" smaller all around for creating a reveal between the wall and the fiberglass diamonds. Then staple the opposite velco patches on the corners the these ply diamonds. Once these are fastened to the wall, it is simple to place the fiberglass diamonds. Sounds complex, but it really isn't. Anyway, make your pattern for as much "edge effect" as possible.
Figure it this way. A diamond with 24" sides and a hypotenuese of about 34" gives you 288 square inchs on the face. The edge perimeter is 82" times say 4" thick. Thats a whopping 328 square inchs just for the edges, which is 40 square inchs MORE than the face!!!! THAT is why I suggest using the diamonds. Not just the pattern, which is cool too, but area of absorption is where its at!!
Anyway, its just a suggestion and there are many many ways to hang it. If you need more, let me know and I would be glad to suggest some alternatives. What I suggested here was off the top of my.head so to speak.
Julian, I'm certainly no expert when it comes to absorption. However, even The Master Handbook of Acoustics states that you will get much more absorption by placing a given square footage in patchs, than you will by using the sqaure footage in one piece. Not only do you gain absorption by virtue of the edge being exposed, every edge creates a diffraction line whereby you gain absorption when the soundwave "wraps" around this edge. This creates an "impedence" difference. This creates absorption benifits also. At least from my understanding, which was directly told to me by an acoustician TODAY! I won't mention names though.

Well, hope this helps a little. Good luck with your project.

fitZ