KMart room treatment

timind · « **on:** 3 Nov 2006, 03:22 am »

The other day I was in KMart and noticed paintings on canvas and thought of acoustic panels. These paintings were close o two inches thick with nothing behind the canvas. I thought about getting some insulation or batting and stuffing them. What do you think of this? Would they provide sound absorption or would the painted surface be too reflective? They were relatively inexpensive.
My acoustic panels are DIY. Approximately 2 inches thick with fiberglass insulation and batting. The largest panel I've built is 48X32 inches made with canvas material that my grandson and I painted. It's on the wall behind my listening chair.

bpape · « **Reply #1 on:** 3 Nov 2006, 03:26 am »

Depending on how thick and how tight the weave is and also how tightly it's stretched, it may still provide some mid/mid-low absorbtion. Most likely it will reflect pretty much everything above 1kHz.

Bryan

DSK · « **Reply #2 on:** 3 Nov 2006, 08:02 am »

Quote from: bpape on 3 Nov 2006, 03:26 am

Depending on how thick and how tight the weave is and also how tightly it's stretched, it may still provide some mid/mid-low absorbtion. Most likely it will reflect pretty much everything above 1kHz.
Bryan

Yes, and 2" thick fibreglass is only effective down to approx 500hz anyway so you would be treating a very narrow range. Best to use broadband treatments wherever possible so as not to skew the response.

MaxCast · « **Reply #3 on:** 3 Nov 2006, 11:37 am »

I think 2" is what is recommended for first reflection points and thicker (as thick as you can go) for corners.

bpape · « **Reply #4 on:** 3 Nov 2006, 11:58 am »

Just to be clear, 2" is only optimally effective down to about 500Hz. Here are the coefficients for 2" OC703 mounted flat on a wall:

0.17 0.86 1.14 1.07 1.02 0.98

As you can see, it still has a .86 coefficient at 250Hz. Extrapolating, you're still going to be about .5 at say 175 or so. Plus, even though it's only doing .17 at 125Hz, if you have enough of it in the room (without getting silly), it still adds up. You are right in that you don't want to skew the response.

Bryan

DSK · « **Reply #5 on:** 3 Nov 2006, 02:01 pm »

Ah, I was referring to the 'batting' referred to by the original poster which is far less efficient than semi-rigid fibreglass panels (eg. .20/125hz & .45/250hz for batts vs .17/125hz & .86/250hz for unfaced 2" OC 703). 2" unfaced OC 706 is slightly lower again (0.16 & 0.7).

Unfortunately, semi-rigid fibreglass is unobtanium here in Oz.

bpape · « **Reply #6 on:** 3 Nov 2006, 02:48 pm »

Can you get 2.5lb or 4.5lb mineral wool? That will work similarly to 703.

Bryan

DSK · « **Reply #7 on:** 3 Nov 2006, 11:55 pm »

Quote from: bpape on 3 Nov 2006, 02:48 pm

Can you get 2.5lb or 4.5lb mineral wool? That will work similarly to 703.

Bryan

Not that I've seen locally. I ended up using 3" & 4" thick fibreglass acoustic insulation batts (flexible, sold in bags of eight).

3" = .31/125hz, .73/250hz, 1.08/500hz.
4" = .43/125hz, .98/250hz, 1.25/500hz.