Glass Fiber Panel

[Cloud_9]

Hello DUC. I would like adhere thin wooden panels to the rigid side of some glass fiber panels I purchased, however, I am really not sure what type of glue to use for this. The reason for attaching rigid wood panels on the rear is to facilitate covering with fabric. Any comments?

Here's a link to the exact item I bought, and thanks to all.

http://www.achatrading.com/insulation/fiberglass.htm

[Craig F]

Usually don't apply to panels just wrap the fabric over the edges and adhere with 3M Super 77 spray adhesive
if you want to use the panels the same adhesive should be fine

[Cloud_9]

Thank you Craig. Do you have any suggestions for a fabric?

Also, hows a .70 NRC? Sufficient for tuning a room?

[flommer]

Here is a link that will take you to a good forum with LOTS of threads discussing what you are after. There are a few guys in the acoustics business, like Ethan Winer (sp?) who often give their advice


Gearslutz Acoustics Forum

[netnoggin]

The John Sayers forum is also a good place to learn more about room tuning, acoustic panels, bass traps, studio construction, etc.

http://www.johnlsayers.com/phpBB2/index.php

Good starting point:

Reference Area - Useful Links

One reason not to put the wooden panel on the back of the fiberglas panel is you will change the acoustic properties of the panel. In most cases, you'll also get better bang for the buck from your panels by mounting them in such a way that they are spaced away from the wall. There a lot of science behind it I won't attempt to explain here. but the concept is the sound hits the panel, is somewhat absorbed, the remaining sound reflects off the wall, and gets further absorbed on the return path. Putting a board on the back of the panel would obviously decrease this benefit.

Spacing is not critical, but to a certain extent the further away from the wall you space it, the more effect it has on lower/mid frequencies. But you're usually limited by how much space you are willing to give up.

[Cloud_9]

Thanks for the links and info guys. Great help.

[O.G. Killa]

Originally Posted by Cloud_9

Thank you Craig. Do you have any suggestions for a fabric?

Also, hows a .70 NRC? Sufficient for tuning a room?

http://www.readyacoustics.com/index....&cPath=26_11_2

http://www.readyacoustics.com/index....cPath=26_11_14

The Average NRC doesn't tell you that much about how the panel reacts at different frequencies. So you need to see a much more detailed spec on the NRC of the product over frequency.

Also, you are using 1" thick panels. if you double them up so it is 2" thick, the average NRC goes up. If you quadruple it so it is 4" thick, the average NRC goes up again!.

You'll notice most sound treatment applications use 2" thick panels at the very least. 1" panels are really only going to stop hi-frequencies.

It sounds like, what you bought is an OEM version of this stuff from owens-corning.

http://owenscorningcommercial.com/da...ly_product=1_1

The most commonly used for acoustics is 703.

You'll notice that on pg 2 of the 700 series product data sheet, it shows the Sound Absorption Coefficients for 703. With 1" of 703 having an average NRC of 0.70 (like what you have) but 2" of the stuff has an NRC of 1.00. NRC ratings are basically a percentage. so an NRC of 0.70 means it absorbs 70% of the sound that hits it.

But as you can see by looking at the chart. Even though 1" has an average NRC of 0.7, it still only absorbs 11% (0.11) at 125Hz. that means if the panel is sitting in the middle of the room facing the speaker, the sound that passes through the panel will have a 11% reduction in volume at 125Hz.

These charts though, just to make you aware, DO NOT tell you the performance of the panel when placed flush up against a wall or suspended out from a wall. All the ratings tests are done in an anachoic chamber with the panel hanging freely. When placed flush up against a wall, they really aren't going to absorb much below 2KHz or 3KHz. The thicker the panel and the more you suspend it off the wall (creating an air gap behind it) the lower the frequency it will absorb.

[Cloud_9]

Originally Posted by O.G. Killa

http://www.readyacoustics.com/index....&cPath=26_11_2

http://www.readyacoustics.com/index....cPath=26_11_14

The Average NRC doesn't tell you that much about how the panel reacts at different frequencies. So you need to see a much more detailed spec on the NRC of the product over frequency.

Also, you are using 1" thick panels. if you double them up so it is 2" thick, the average NRC goes up. If you quadruple it so it is 4" thick, the average NRC goes up again!.

You'll notice most sound treatment applications use 2" thick panels at the very least. 1" panels are really only going to stop hi-frequencies.

It sounds like, what you bought is an OEM version of this stuff from owens-corning.

http://owenscorningcommercial.com/da...ly_product=1_1

The most commonly used for acoustics is 703.

You'll notice that on pg 2 of the 700 series product data sheet, it shows the Sound Absorption Coefficients for 703. With 1" of 703 having an average NRC of 0.70 (like what you have) but 2" of the stuff has an NRC of 1.00. NRC ratings are basically a percentage. so an NRC of 0.70 means it absorbs 70% of the sound that hits it.

But as you can see by looking at the chart. Even though 1" has an average NRC of 0.7, it still only absorbs 11% (0.11) at 125Hz. that means if the panel is sitting in the middle of the room facing the speaker, the sound that passes through the panel will have a 11% reduction in volume at 125Hz.

These charts though, just to make you aware, DO NOT tell you the performance of the panel when placed flush up against a wall or suspended out from a wall. All the ratings tests are done in an anachoic chamber with the panel hanging freely. When placed flush up against a wall, they really aren't going to absorb much below 2KHz or 3KHz. The thicker the panel and the more you suspend it off the wall (creating an air gap behind it) the lower the frequency it will absorb.

Great! This info helps a great deal.

The panels I purchased are actually 2" inch versions of the product I provided in the link.

I ditched the idea of glueing them to a rigid board of wood and went with Craig's suggestion using Super77, which I must say, is super.

Regarding the space between the acoustic panel and the wall, I am figuring that 4" is as far as I can go without compromising to much space.

Gonna check out those links now.

[O.G. Killa]

cool. I usually just build a frame around them out of 2" x 1" strapping. The frame also gives you something to use as a hanger and you can staple the fabric right into the wood. Also the ready acoustic fabric bags have a strap across the back for hanging.

whatever you do, I don't recommend gluing them to the wall. It is a mess to take down, move, change around, etc...

Also, using a rigid board would kill the effectiveness of the panel, especially if you put the board on the front side. It would basically just act as a reflector at that point and not absorb any sound.

Since these panels are "frictional" absorbers, they absorb sound energy as air passes through them and transfers that energy into heat (very, very tiny amounts) within the fiberglass. Putting a board over the front pretty much stops any air from flowing through it and so will pretty much make it ineffective at absorbing high and mid frequency. The same thing goes for whatever material you cover them with. The less air that flows into the panel itself, the less effective it is.

[Cloud_9]

Originally Posted by O.G. Killa

cool. I usually just build a frame around them out of 2" x 1" strapping. The frame also gives you something to use as a hanger and you can staple the fabric right into the wood. Also the ready acoustic fabric bags have a strap across the back for hanging.

whatever you do, I don't recommend gluing them to the wall. It is a mess to take down, move, change around, etc...

Also, using a rigid board would kill the effectiveness of the panel, especially if you put the board on the front side. It would basically just act as a reflector at that point and not absorb any sound.

Since these panels are "frictional" absorbers, they absorb sound energy as air passes through them and transfers that energy into heat (very, very tiny amounts) within the fiberglass. Putting a board over the front pretty much stops any air from flowing through it and so will pretty much make it ineffective at absorbing high and mid frequency. The same thing goes for whatever material you cover them with. The less air that flows into the panel itself, the less effective it is.

Thanks OG, I killed the backing panel idea. The frames on the ready traps site look really nice, however shipping to PR is absolutely prohibitive. $40.00 for one $36.99 frame, go figure. What exactly is 2" x 1" strapping? This could be my solution.

I am thinking of attaching two of these 2" thick fiber glass panels together to create some 4" base traps, this way effectively treat my rooms corners. Considering that the fiber glass panels have a "rigid" side to them, do you recommend attaching them with the rigid sides facing eachother? This way the "softer" sides look towards the room and the rear looks towards the empty space between the panels and the wall. Make Sense?