IIG Rigid Rockwool - tell me what you think

[analog orange]

Okay, I've been lurking here for about a month and am finally about to take the plunge and build a bunch of bass/broadband traps. I was able to find 4" 4# rigid rockwool for 92 cents a square foot. And 8# of the same for a buck ten a square foot. The brand is IIG and Bob Gold's page lists the freqs of both as:

4" 4# 0.88 1.14 1.17 1.08 1.06 1.10 1.10

4" 8# 1.11 0.91 1.03 1.03 1.06 1.07 1.00

I've got some really weird junk happening in the room around 65hz so I was leaning towards the 8#. Are they really that different though?

The room's around 16'x14"x20"x7"x7" So basically a 16x14 room with a 7x7 jetty. The floor is bamboo wood and the walls are all sheetrock. There is a 5x3 window at the long end of the jetty. And the walls angle at about 4 feet off the ground up to the ceiling all around. This is a rec room over a garage.

I was going to buy around 20 bats of the stuff, cover them in fabric and place them all around the room. Some on the wall, some on the floor. What do you all think? I went and looked at this particular rockwool today and it seemed as tough or tougher than 703. I'll get the exact measurment of the room and a pic if you think that would help.

Thanks in advance to anyone and everyone that has any advice to offer. I haven't been on a board regularly for years (when I used to use PARIS) and you all seem to be a great bunch of people. Thanks.

Justin

[Ethan Winer]

'm sure that stuff will be fine, but never take absorption data as absolute. Labs vary all over the place, especially at low frequencies. The same material could measure 1.0 at one lab and 0.80 at another. Really. It's not an exact science the same way as measuring frequency response or distortion. If you care, much more here:

Alternative Test Methods for Acoustic Treatment Products

--Ethan

[Glenn Kuras]

I've got some really weird junk happening in the room around 65hz so I was leaning towards the 8#. Are they really that different though?

For 65hz use the 8# and make the panels 6" thick and straddling as many corner as possible. One other thing you could do, which will work well at 65 hz is to use the 4" and cut it into 17x17x24 inch triangles and stack them floor to ceiling.


Glenn

[analog orange]

Thanks guys! I'll be getting on this pretty soon. I'll post my results when I get done. Thanks again.

[Glenn Kuras]

No problem and let us know if you have any other questions we can help you with.

Glenn

[analog orange]

I've got a few more questions.

What do you recommend to stick two pieces together? I'm going to make the 6" traps tomorrow and I'll need to sandwich 2 pieces of 3" to do it. I was going to get some spray adhesive. Necessary?

From there I was going to wrap them initially in either cotton batting or weedblock to contain the fibers, and on top of that some heavy cotton fabric. Any issues there?

Finally are there any deleterious effects to piercing the Rock wool? I plan on hanging some 3-4" broadband absorbers from the ceiling. Would running a long carriage bolt or dowel through its width or length negatively affect it's performance?

Thanks again.

Justin

[Glenn Kuras]

What do you recommend to stick two pieces together? I'm going to make the 6" traps tomorrow and I'll need to sandwich 2 pieces of 3" to do it. I was going to get some spray adhesive. Necessary?

No need for any kind of spray adhesive. Just put them together..

From there I was going to wrap them initially in either cotton batting or weedblock to contain the fibers, and on top of that some heavy cotton fabric. Any issues there?

seems fine to me.

Finally are there any deleterious effects to piercing the Rock wool? I plan on hanging some 3-4" broadband absorbers from the ceiling. Would running a long carriage bolt or dowel through its width or length negatively affect it's performance?

yes it will leak radiation!!!!!!!!!!!!
No there should be no problems.

Glenn

[analog orange]

That's a relief! Radiation was my chief concern!

Thanks!