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Hi Ethan/Jon/Others,
I've been reading many archived threads lately but can't seem to find an answer to the following question:
If I'm going to build 2 corner traps using 4ft x 16in x 3in Roxul "Safe'n'Sound" (that was all the Building Centre here had in stock, but I think it has reasonable measurements), would there be better low frequency absorption with a) 6" deep and 16" wide, or b) 3" deep by 32" wide?
density 2.5 pcf (40 kg/m3)
125hz 0.52
250hz 0.96
500hz 1.18
1000hz 1.07
2000hz 1.05
4000hz 1.05
NRC 1.05
-from bobgolds.com
I have 20 wool panels in the above dimension to work with. I'm planning on building six 4' x 16" x 3" to counter the first reflections of the front and side wall, and the second side reflections. I know they'll provide better LF absorption if placed away from the wall, but I don't have that option, so, would six 6" panels placed on the wall be OK or too much?
My bedroom system 12 x 17 (avg) x 9; painted drywall; carpet; queen size bed with upholstered wooden frame and 18" springed mattress; front wall is an exterior with a 5'x5' window.
Thanks in advance.
Follow Ups:
> would there be better low frequency absorption with a) 6" deep and 16" wide, or b) 3" deep by 32" wide?
Yes and Yes. The deeper and wider, the better. Always. So make them as deep and wide as you can fit.
> would six 6" panels placed on the wall be OK or too much?
Not too much for a room that size.
--Ethan
What I've done so far... one 16x48x6 in each of the front corners, one at the front wall/floor junction, one at the first side reflection points (angled toward the speakers), and one 16x48x3 at the first front wall reflections and 8in from the walls.
The image focus and depth improved quite a bit. It actually brought a very broad and lasting grin to my face. There is a slight boominess still with acoustic double bass. I'm guessing that going with 8ft x 32in x 3in corner panels could take care of this.
And there still exists a flutter echo no matter where I stand in the room - my GF and I were having one of those talks yesterday in the room and whenever one of us finished a statement that 'boing' would be there. So my question is would adding many (5 per wall) smaller (16x16) 3in panels reduce the flutter? Would I need them to be 6in deep?
There is such a thing as too much of too shallow (thin), and increasing the area with out increasing or maintaining the depth could be a problem overall.
If you are hearing a "boing", instead of discrete flutter echoes, then I suspect that your problem is more in the nature of corner echoes, and placing some panels in the corners would be the best approach. Experiment with what wall they are 'flat' against, the best orientation may not be across the corner at a 45 degree angle.
As for the 1st reflection points, a width of 32" would be even better, as long as it was 6" deep or more. 16" width will not absorb down to a very low frequency, thus my recommendation for more width (30") than the typical 2X4 foot panels afford. Your 16" panels are even smaller, and thus more problematic.
Jon Risch
That 'boing' is actually a highly pitched ringing which transitions to a boing. It's more prominent with a sharp clap of the hands compared to talking voice. Would this phenomenon be the flutter echo?
in the "listening room" when I moved into my newly built house, 20 years ago. In other words, when I clapped my hands, I'd get ringing (this was a room about 17' x 27', with a pitched ceiling (down the length) about 16' high in the centre and 9' high at the sides).
I solved the flutter echo problem by creating a wall hanging made of 1" thick cork, painted in bright colours, glued to framed masonite (to stop it curling) which was about 15' long & 6' high.
This "work of art" would appear to have stopped HF reflections between the long walls - so when I clap my hands now, there is no ringing.
Regards,
Andy
Yes, the "boing" sound is flutter echo. You can hear a demo in this video:
http://www.vimeo.com/1522217
--Ethan
I think 30 percent surface coverage is considered the minimum to reduce flutter echo to a reasonable level.
--Ethan
nt
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