DIY absorber and diffusor help

[crackyflipside]

Ok, so I pretty much got the absorber idea down-packed for multichannel (at least I think I do).

-Treat first reflections from L/C/R on walls, floor, and ceilings for both rows of seating. I'll be using 3" OC703 for walls, carpet on floor, 2" OC703 on ceiling.

-Treat front wall / screen wall and use acoustically transparent screen. Using 3" OC703 covering the whole area directly behind the screens and making cutouts to fit the future 3 x TMWW towers. (I already calculated how the wall distance would affect the FR of the towers assuming the 3" OC703 and it looks fine)

Now, diffusors are a whole different story. I really really really like the look of Primitive Root Diffusers so I would definitely take the time to DIY some panels. The thing is, I don't really have a clear idea of where to place them or how much to use. Now, when I talked to Chasw98, he basically told me absorbtion is more important in the front and diffusion is more important in the rear; he gave some analogy of 'playing music while sitting on the edge of a cliff' sound is what I am aiming for. So he said the diffusors should be located in the rear part of the room near the rear and side surrounds.

So this is what I'm asking:

1. Am I missing anything in the absorbtion area?

2.How to make a Primitive Root Diffusor (skyline type)?

3.Where exactly do I put the diffusors assuming a 7.1-type multichannel audio?

[Habs4life]

Cracky ,Here is a skyline calculator.http://www.mhsoft.nl/DiffusorCalculator.html here is some more info http://www.mhsoft.nl/RoomAcoustic.asp

[crackyflipside]

Thanks for that info, now to find out how to use these programs to suit my needs. More reading will be done!

[chasw98]

Chris:
Here is some reading to put you to sleep...............

http://www.jdbsound.com/art/art517.html

http://www.primacoustic.com/primer.htm

http://www.electroacoustics.co.uk/article/essroom.htm

http://www.asc-studio-acoustics.com/surround6.htm

Chuck

[chasw98]

And Chris, if you want to hear a real LEDE instal, we should go on a road trip to Boynton Beach and visit here http://www.whateverwayproductions.com/green/studio.htm

[crackyflipside]

Ok so after reading all the links Chuck gave and all the links I could find on my own, I started mapping out where the acoustics would go.



Yellow is absorbtion and blue would be diffusion. Green is where the speakers are located.

I didn't put up the picture here where I mapped out all LCR first reflections because it would be nearly impossible to decipher unless I had it at a really large image size. What I did was find all first reflections from the LCR and put absorbtion there. The screen wall looks wavy because with all the cutting I do of this OC703, it can be added to the screen wall for more absorbtion and some very light diffusion.

On the side surrounds, I was contemplating whether to leave the space empty in between the surrounds or put more random diffusion. Maybe a peice of warped plywood could be put there (kind of like a half a cylinder) to provide a better surface than just flat drywall.

The cavity I have to work with is 6" on the side walls so the absorbtion would be 3" OC703 + 3" airspace -> Drywall. On the side walls, the blue diffusion will be a mix of styrofoam built skyline diffusors and improvised diffusors (shelves in the back)

[chasw98]

I'd say that looks real good Chris. Very well thought out and makes a lot of sense. Not too much, not too little and if you need a little tweaking it is possible within the famework of what you propose. Good job!

Chuck

[crackyflipside]

I'd say that looks real good Chris. Very well thought out and makes a lot of sense. Not too much, not too little and if you need a little tweaking it is possible within the famework of what you propose. Good job!

Chuck

You know what, now that I thought about it, would slightly angling the absorption on the side walls be beneficial or wouldn't make a difference?

[chasw98]

It does not hurt at all. What you are doing is breaking the plane of parallel by doing doing that and it can help quite a bit.

[crackyflipside]

It does not hurt at all. What you are doing is breaking the plane of parallel by doing doing that and it can help quite a bit.

Even if I am just breaking the plane of paralel with a soft surface like rigid fiberglass?

[chasw98]

Even if I am just breaking the plane of paralel with a soft surface like rigid fiberglass?

Believe it or not, it helps.

Chuck

[Rolyasm]

Hey Cracky,
Looks like you are doing great work. I am helping a friend soon to treat his room, so I might call on you for some advice.
Is that a subwoofer? 4 drivers in array? If so, I'd be interested to know how it sounds and what your volume is and type of drivers. Also, from your picture, it looks like you have 4 surround speakers,as well as two rear, for a 9.1 setup? Am I seeing that correctly?
Roly

[Bob]

The only problem that I see with your undertaking is that you are treating the least important "problem areas" typically encountered in a dedicated room.

Bass mangement is far more important than first reflections. Plus, looking at your room layout and seating positions, I'm not so sure diffusion panels in the back are of much importance in your circumstance. Treating the ceiling with diffusion could possibly do more than the back of the room.

First treat the problem areas for bass. That would be corners and wall ceiling junctions. Despite their names, bass traps don't take away bass. They help make it more defined and usually make your mid-range sound much better.

Before starting a DIY room treatment I would suggest reading all the info at the real traps website (you can use that info for your DIY panels). And, read all the info on the Rives website. If you really want to do it right, pay for the Rives 1st level. They don't sell any brands and it can all be DIY.

If you don't want to go the Rives method because of cost there is a best alternative with detailed instructions available for free on the net. Go to audioperfectionist.com and download the second free journal. I have personally been in Richard's room and have heard the results. It is the second best sounding room I have ever been in, and the best by far in a persons home. Plus, there is no visual signs that the room has been optimized for sound, with the exception of the small ASC tube traps he uses in his back corners.

[J-Dub]

You know what, now that I thought about it, would slightly angling the absorption on the side walls be beneficial or wouldn't make a difference?

Sorry for pulling up old post but I did.

My understanding would be that angeling the absorption panels will alter several things. As far as helping or hurting I don't know. One is it should raise the absorption coefficient along the panel, more at the raised end due to the gap behind it. two is that refraction will come into play at different levels along the angled panel. (probably minimal effect except for the adjacent room) Three is that it should change the angle of reflected waves slightly (mainly axial and tangential) and should be taken into consideration on the listening position.

Just my .02