Rear Wall Diffusion

Velvet Elvis · Post by **Velvet Elvis** » Thu Jul 31, 2003 6:12 am

Hey all...

I was looking at this site today Primacoustic.

I was wondering about their back wall diffuser... I mean... would it be as adequate to take a 4x8 sheet of MDF and fasten various length dowels (square or round) to the MDF (on end) so that you get the same sort of diffusion? It seems that their box is basically just a series of different depth valleys etc... Same sort of principle as putting a book case or two at the back of the room.

My thought is it would be way easier and cheaper to take 1x1 stock and rip it down to various lengths of 8 inches or shorter and screw/glue them on end side by side until I fill up an entire 4x8 MDF with 'random' height dowels... would this work?

Is this what I would want to be doing in a 10x14 control room assuming I use some high/mid absorbers elsewhere etc?

Velvet Elvis

laptoppop · Post by **laptoppop** » Thu Jul 31, 2003 6:29 am

My room is a similar size. I decided to go for absorbtion on the back wall behind the mixing station instead of diffusion because I didn't want any near field echos - diffuse or otherwise. I'm using 4" of Owens Corning 703 rigid fiberglass wrapped in muslim spaced about 4" off of the back wall.

I'm using mostly panel absorbers on the walls and in the corner, with a bookcase area in one spot for some natural diffusion (stands, cases, books, cables).

-lee-

Velvet Elvis · Post by **Velvet Elvis** » Thu Jul 31, 2003 6:33 am

Lee...

Thanks for your comments... I'm hoping to have a couch etc in the back area of my room which will act somewhat as an absorber... so I wasn't sure whether more absorbtion or whether diffusion was the way to go. I don't want to make the room completely dry, but I do want to have a 'clean' mix position.

Velvet Elvis

knightfly · Post by **knightfly** » Thu Jul 31, 2003 2:45 pm

Hey V-E - Your room is too small to benefit from diffusion at the rear - any time you have less than about 25 feet round trip from the BACK OF YOUR HEAD to the back wall and return (12-1/2 feet each way) you end up with early reflections muddying your imaging. We always recommend sticking with absorption in smaller rooms because of this.

For brightness, if they are splayed properly, slat absorbers at the front sidewalls are OK, because any early reflections off them would be re-directed AWAY from the mix position, and get absorbed before getting back... Steve

audio hobbit · Post by **audio hobbit** » Thu Jul 31, 2003 3:02 pm

FWIW, The folks who built the place I work out of went with diffusion in a 15 x 19 room, and I have spend a good part of the week tearing it down and building a big absorbtive panel along the back wall.. feels way better and I am still finishing it out. ( the control room has a full sizes couch and a 2 seater couch as well, and it did not give enough absorbition, I just put in 2 layers of 703 fsk and an air gap.)

Velvet Elvis · Post by **Velvet Elvis** » Fri Aug 01, 2003 12:54 am

Thanks all for the replies

That makes total sense

So... given my room design, what would you suggest for acoustic measures? I'm not sure that I will be able to splay the ceiling (its only 8 feet high)... but you can see the wall angles.

(The green lines are where my HVAC is located... a pain, but its got to be there)

Thanks!

Velvet Elvis

zikaj · Post by **zikaj** » Fri Aug 01, 2003 1:26 am

Elvis-

Here's some brain food.

"It seems that their box is basically just a series of different depth valleys etc... Same sort of principle as putting a book case or two at the back of the room. "

Yes and no. While I can't vouch for the primacoustic product- as I've tried over and over to get an answer from them "is your diffusor based on sound quadratic math nerd stuff?"- these diffusors are not random. They are based on quadratic residue equations. (n^2 modulo p).

I am RE-opening business building quadratic diffusors (and other stuff....shameless plug...I know) in the next 3 weeks. I have several of them at my home. (the rest burned up in a fire....long story...).

Anyway, you see I have an interest in this diffusion thing, and I want to say that STEVE IS RIGHT. 100%. AS USUAL.

You'd be wasting your time putting up diffusion without proper room length behind your head.
My home 'studio' is small too, and I absorb behind my head.

Oh- the 'bookshelf of books' approach. I have heard it works. Literally- heard. It does work to a point. So does putting up some random boards and 'stuff', to a point. But it certainly isn't controlled. Putting up a big poly works too. And even if these DIY home solutions don't create a wonderfully diffuse sonic field enhancing spacial and frequency response of the given space, they'll at least cut down slappy echos and reflections.

Then again, if you're spending time to build a studio space, why cheap out and put up a bunch of crap on the rear wall/side wall/wherever.

...did I mention that a live room would benefit from some quality, affordable diffusors...?

Atleast thats what I heard.

JeffZ

Velvet Elvis · Post by **Velvet Elvis** » Fri Aug 01, 2003 1:34 am

zikaj,

Thanks for the info... yeah I'm guessing I will steer away from diffusion given everyone's advice.

The only reason I asked about the primacoustic is that I remember seeing at their site that they called it "semi-random" so I'm not sure how much math actually went into the design... that would seem calculated to me and not "semi-random".

Anyhow... I can deal with using absorbtion instead... no problem.

I just need to get recommendations as to what walls to treat (as per my drawing) and with what.

Velvet Elvis

zikaj · Post by **zikaj** » Fri Aug 01, 2003 4:17 am

[The only reason I asked about the primacoustic is that I remember seeing at their site that they called it "semi-random" so I'm not sure how much math actually went into the design... that would seem calculated to me and not "semi-random". ]

I'm with you on this. They call it "semi-random" and a true quadratic in the same sentence. Atleast thats how I remember it. I emailed them several times to inquire to get a few before I built my own. They had to answer.

Great looking space, btw. Great use of what you have.

Jeff