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Rigid vs Fluffy Fiberglass
Old 22nd October 2013
  #1
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Rigid vs Fluffy Fiberglass

If sacrificing a bit of room space at the boundaries is not an issue, what is the purpose of using compressed fiberglass (19500 pa.s/m2) over fluffy (6000 pa.s/m2) ?? I recently build four panels using 16kg/m3 fluffy (48"x40"x8" ) & installed one behind each speaker on the front wall & one in line with each speaker on the left & right walls (all spaced 8" from the walls) & the improvement is quite substantial than just a 4" rigid panel made using compressed fiberglass (48kg/m3) at the same positions
Im yet to measure before vs after using REW but the improvement has got me thinking if I have kinda wasted 2 dozens of panels which I have already made using rigid fiberglass & straddled at the wall/ceiling junctions. Does compressed fiberglass have a point of diminishing returns after a particular thickness?

https://db.tt/N6en17Vx


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Old 22nd October 2013
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Old 22nd October 2013
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Quote:
Originally Posted by Jens Eklund View Post
Yes thats what I used for simulating & decided to try using fluffy..
Something is preventing from attaching the screenshot here so I have included the link to my dropbox...

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Old 22nd October 2013
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Well, then you know that low flow wool is the better choice if you want to absorb a wide range, assuming you have the depth to spare.
Old 22nd October 2013
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Quote:
Originally Posted by Jens Eklund View Post
Well, then you know that low flow wool is the better choice if you want to absorb a wide range, assuming you have the depth to spare.
Exactly !

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Old 22nd October 2013
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Rigid vs Fluffy Fiberglass-uploadfromtaptalk1382447556169.jpg

Rigid vs Fluffy Fiberglass-uploadfromtaptalk1382447588421.jpg

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Old 23rd October 2013
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Quote:
Originally Posted by Jens Eklund View Post
Well, then you know that low flow wool is the better choice if you want to absorb a wide range, assuming you have the depth to spare.
Adding 1" thick slats in the MLS sequence will only scatter the mids/highs or can we expect some benefit in the bottom end as well?
Any link on before vs after installing slats?

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Old 23rd October 2013
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If you refer to a sequence that results in a 50% open area; there will be no (or extremely limited) additional absorption in the lows and the only reflection you´ll get (partly scattered) is in the frequency range where the wavelength is small (about ½ lambda or larger) compared to the slat width. A slotted panel with for example 100 mm slat widths and a 50% open area, would act more or less as a broadband absorber below about 1,5 - 2 kHz. Not ideal in a normal situation. A more useful cutoff between absorption and reflection (and hopefully at least partly scattered) would be at around 200-300 Hz (close to the Schroeder frequency for a normal room size).
Old 23rd October 2013
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Quote:
Originally Posted by Jens Eklund View Post
IA more useful cutoff between absorption and reflection (and hopefully at least partly scattered) would be at around 200-300 Hz (close to the Schroeder frequency for a normal room size).
And that would be ?

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Old 23rd October 2013
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About 20-25% open area. This would also result in an increased absorption in the lows without being tuned to a high Q device.
Old 23rd October 2013
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Quote:
Originally Posted by Jens Eklund View Post
About 20-25% open area. This would also result in an increased absorption in the lows without being tuned to a high Q device.
Awesome. So say 2 inch wide slats with one inch gaps in series? Does the thickness of the slat matter?

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Old 23rd October 2013
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Quote:
Originally Posted by Jolida View Post
Awesome. So say 2 inch wide slats with one inch gaps in series? Does the thickness of the slat matter?

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If you’re after some scattering; I would randomize the pattern a bit more. If you only want to avoid absorption above the modal range; it´s not important.

Thickness of the slats (length of the "neck" of each HH resonator i o w) matters sometimes when the perforation percentage is low (high Q) and precise tuning is required, but not much in this case.



EDIT: Oh; and I would try to get closer to 20-25% open area But even better would be to figure out what the room needs based on measurements.
Old 23rd October 2013
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Quote:
Originally Posted by Jens Eklund View Post
If you’re after some scattering; I would randomize the pattern a bit more. If you only want to avoid absorption above the modal range; it´s not important.

Thickness of the slats (length of the "neck" of each HH resonator i o w) matters sometimes when the perforation percentage is low (high Q) and precise tuning is required, but not much in this case.



EDIT: Oh; and I would try to get closer to 20-25% open area But even better would be to figure out what the room needs based on measurements.
Some pictures would be of great help Jens. Thanks as always..

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Old 23rd October 2013
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Quote:
Originally Posted by Jolida View Post
Awesome. So say 2 inch wide slats with one inch gaps in series?
2+1 is 30%, 3+1 is 25%, 4+1 is 20% of open area.
Quote:
Originally Posted by Jolida View Post
Does the thickness of the slat matter?
....
Its depends on thickness.. so yes... if some "slats" has thickness of 4", this will be significantly different compared to 1/2" thick slats.



Old 24th October 2013
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Quote:
Originally Posted by boggy View Post
2+1 is 30%, 3+1 is 25%, 4+1 is 20% of open area.

Its depends on thickness.. so yes... if some "slats" has thickness of 4", this will be significantly different compared to 1/2" thick slats.



Whoa ! Thickness of 4" or width of 4" ?
I read somewhere that using 2" wide slats of 1" thickness spaced 1" apart do a pretty good job. Thickness I mean as in depth of slats...

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Old 24th October 2013
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Quote:
Originally Posted by Jolida View Post
Whoa ! Thickness of 4" or width of 4" ?
.......
I said thickness of 4"... as example...
Old 24th October 2013
  #17
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Quote:
Originally Posted by boggy View Post
I said thickness of 4"... as example...
Never heard of or seen a 4" thick slat ever. Any pics?

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Old 24th October 2013
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Quote:
Originally Posted by Jolida View Post
Never heard of or seen a 4" thick slat ever. Any pics?

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Studio Sonic Dream, RES Media, Novi Sad, Serbia:

Old 25th October 2013
  #19
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Quote:
Originally Posted by boggy View Post
Studio Sonic Dream, RES Media, Novi Sad, Serbia:

Lovely. Those are like 4" deep by 2" wide?

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Old 25th October 2013
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Quote:
Originally Posted by Jolida View Post
Lovely. Those are like 4" deep by 2" wide?

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about 4" (varied following Schroeder QRD sequence), thickness is 19mm (about 3/4")
Old 25th October 2013
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Quote:
Originally Posted by boggy View Post
about 4" (varied following Schroeder QRD sequence), thickness is 19mm (about 3/4")
Sorry, dint get that :confused:

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Old 25th October 2013
  #22
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Quote:
Originally Posted by Jolida View Post
Sorry, dint get that :confused:

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I don't want to go too much to the off topic, so, more info you already have here: MyRoom Acoustic Design
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