Acoustics project (with url now)

BR · Apr 13, 2006

Hey there guys,
I just thought I should share this.

I just finished the first phase of this project about 2 weeks ago and wanted to post some pics.

This is a church down in Miami that I've visited a few times, I mean, a lot of times, and always had major issues with the acoustics of the place.
Just to give you guys some feedback on the horrendousness of the thing here is the description of the room.

Length - 50 ft
Width - 24.5 ft
Height - 14.5 ft.

Floor- Thin commercial carpet
Ceiling - concrete double T bars (thats the best description I can give)
Side walls - untreaded concrete blocks
Front and back walls - drywall

There are about 70 cussioned seats in there and thats about all the treatment present.

Initial tests gave me a RT60 of about 3.2s on vocal range. Vocals and speeches were almost entirelly inteligible when going thru the system.
Band sets were incredibilly loud and extremelly unclear.

Some of the restrictions on this projects (besides budget, off course) were that everything needed to be mobile, since they are planning on moving soon. So permanent installations had to be kept to a rediculous minimum as you will see in the pics.

So, the first phase was for RT and flutter control.
For that we built panels measuring 2'x4' with 2" of rigid fiberglass. The frames were made out of 3/4" plywood and the fabric was Guilford of Maine.

Here are the rough plans for the panels:
www.braudio.com/forumfiles/Church/Panel-Assembly.pdf
and some pics:
www.braudio.com/forumfiles/Church/PICT0757.JPG

These panels were mounted on rails made out of 2x4 cut in a 45degree angle with oposing angle on the back of the panels. See pic.
www.braudio.com/forumfiles/church/PICT0765.JPG

After treatment, I still haven't done any measurements. That will come up in 2 weeks, but my assessment is that I've probably brought RG60 down to about 1.5s and flutter is minimal. The improvement was so great that they realized they (band) will need to get better now.... :green:
Overall inteligibility for both music and speech has increased greatly and the overall volume of the room has drastically changed..

Here are some pics of the room. Hopefully in order of progress.
www.braudio.com/forumfiles/Church/ceilingdetail1.jpg
www.braudio.com/forumfiles/Church/church1.jpg
www.braudio.com/forumfiles/Church/PICT0764.JPG
www.braudio.com/forumfiles/Church/PICT0765.JPG
www.braudio.com/forumfiles/Church/PICT0771.JPG
www.braudio.com/forumfiles/Church/PICT0772.JPG
www.braudio.com/forumfiles/Church/PICT0773.JPG
www.braudio.com/forumfiles/Church/PICT0774.JPG

Hope you like it..
I'll post measurements as soon as I have them.

Phase 2 will be low end control

Phase 3 will be final tweaks and decoration.

Gil

Guest · Apr 13, 2006

[quote author="BR"]
This is a church down in Miami that I've visited a few times,
....
Length - 50 ft
Width - 24.5 ft
Height - 14.5 ft.
....
Floor- Thin commercial carpet
Ceiling - concrete double T bars (thats the best description I can give)
Side walls - untreaded concrete blocks
Front and back walls - drywall
[/quote]
Hi, Gil.
Nice info, acoustics solved, but in the somewhat Sabinian sense

There is lack of unilaterality in the acoustic design.
What I mean is, that you reduce reverbation time on the price of low volume level.
(There is relation between volume and reverbation in statistical formulas, developed by W.C.Sabine from MIT ïn the 1900-ies.)

Some unilaterality can improve acoustic.
What about front wall and floor ? I mean, that it may be reflective.
Ceiling is good (diffusive), but can be reflector at center, but side walls may be somewhat diffusive also.
But diffusors may be only in the corners. (first reflections planes (center sections) must!!! be reflective) Back wall may be Diffusive/absorbtive.
Use somewhat like D Antonio s "magnitude diffusers"

... But it is only my subjective phantasy...

xvlk

BR · Apr 13, 2006

thanks for info..
I actually used Sabines equation to come up with a rough estimate of the amount of treatment that I would need, and it turned out to be about 15% of the area of the walls.

When I mentioned about the volume being reduced, I didn't mention that it is actually good now. It was way too loud before and it is now no where neer quiet.

It's hard to see in the pics, but I actually spaced the panels not facing each other on parallel walls, which helped tremendously with flutter.
Also by having these panels somewhat separated, they are automatically doing some diffusion due to the edges of the panels. My original idea was to go with 2'x2' panels, but that would have been too much.

The only diffusion that I can add to this room would probably be some polys between the panels. Probably made out of 1/4" or 1/2" plywood curved to about a foot on the center..

We'll see....

thanks
Gil