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[Tom C]

Hello,
I'd like to rebuild my room (16.5 ft x 12.3 ft x 8.27 ft, the
ceiling drops down to 5.25 ft (that's the back wall) on the last
6 ft of the longer dimension).

The side walls and the ceiling will get some mid/high freq
absorbers.
I have room for about 20" worth broadband absorbers (something
similar to 703 rigid fiberglass) for the front/back wall.

What's the best way to split those 20"?

Both back and front 10"?
Back 15", front 5"?

I couldn't find anything about this special question.

Any ideas on how to do it and why are much appreciated.

[franman]

Tom,

Good question. We typically try to address corners in smaller CR's. If you could give up Corner traps that are approx 24" deep at the maximum, I would suggest "cutting" the corners with 4" of 704 or 705 and then filling the space behind the Rigid (that cuts accross each corner) with loose, hanging baffles of R11 unfaced batt insulation. I will cover this porous corner trap in the future bass trap post!!

On the remainder of the front wall, place 4-6" of 703 on the flat. We typically would look at appropriate diffusor installations (see other posts on diffusion) for the center area of the rear wall.....

Don't forget to address the first reflection points along the front side walls and ceiling!!

cheers!

[Tom C]

franman wrote on Sun, 03 September 2006 05:45

Tom, Good question. We typically try to address corners in smaller CR's. If you could give up Corner traps that are approx 24" deep at the maximum, I would suggest "cutting" the corners with 4" of 704 or 705 and then filling the space behind the Rigid (that cuts accross each corner) with loose, hanging baffles of R11 unfaced batt insulation. I will cover this porous corner trap in the future bass trap post!!

That'll translate to a 48" front face, that'll be no problem with the front wall corners.
On the back walls space is a bit tighter, but I'll try to make it as close as possible to 24".
Or maybe not in a triangle shape but a pentagon shape.

Quote:

On the remainder of the front wall, place 4-6" of 703 on the flat. We typically would look at appropriate diffusor installations (see other posts on diffusion) for the center area of the rear wall.....

My plan was to install absorbers first and add diffusors later 'by ear'. I already did this for a friend and was surprised how far you can go without any meters.
But if you say (besides the corner traps) the back wall doesn't need any absorbers that's fine.

Quote:

Don't forget to address the first reflection points along the front side walls and ceiling!! cheers!

The side walls are covered already, the ceiling will be done when I've decided on the size and the look of the back wall treatments to have a similar design.
Even it's for the acoustics it should look pleasing.

Thank you a lot for the information and your time, it's mucho appreciated.

[franman]

Your welcome! Give us a report as things move along, okay?

[Tom C]

franman wrote on Tue, 05 September 2006 02:13

Your welcome! Give us a report as things move along, okay?

I'll start early October and try to document the process with
some photos which I'll post here for your entertainment.

[RKrizman]

For the corner traps it okay just to have the 703 without any plywood backing or anything?  Does the latter affect the bass absorption?

thanks,
R

[franman]

For these types of porous corner traps we do not back the 703 placed in the framing bays. We "loosely fill" the cavities behind with unfaced batt insulation. Hanging batts from the ceiling is a good approach. Sometimes we add a 2" layer of rigid fiberglass directly to the inside shell surfaces as well. The level, amount and type of materials is budget driven.