Rock wool vs. Acoustic cotton vs. OC703 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 14 Old 01-28-07, 10:57 AM Thread Starter
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Rock wool vs. Acoustic cotton vs. OC703

Is there any real difference between Rock wool, Acoustic cotton and OC703? Is one more efficient then the other or more efficient at different frequencies? Where can I find info on this?
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post #2 of 14 Old 01-28-07, 11:06 AM
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Re: Rock wool vs. Acoustic cotton vs. OC703

Check out Bob Golds' site - www.bobgolds.com and look under the coefficients link.

If all else is equal (thickness, mounting, and density), the cotton will have a slight edge in the lower frequencies if we're speaking of 1 and 2" 3lb density materials. As you get thicker, the different materials tend to be more readily avialable in different densities so it's harder to compare. The best solution depends on the application and what specifically you're trying to accomplish.

For instance, 6" of OC703 is pretty effective and even across the board assuming an A mounting flat on the wall. 5.5" of 1.5lb acoustical cotton will do just as well over most of the band but has a hump in absorbtion around 250hz.

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post #3 of 14 Old 01-29-07, 02:44 PM
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Re: Rock wool vs. Acoustic cotton vs. OC703

That's a great link bpape. I have been looking for the specs on John's Manville as it is the only thing I can get around here.

Thanks
John
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post #4 of 14 Old 01-29-07, 03:55 PM
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Re: Rock wool vs. Acoustic cotton vs. OC703

It's kind of a hobby for Bob. It's a nice reference when you want to compare things. Don't get too hung up on tiny differences as some were done in different labs and certainly on different days. They're also only as good as the manufacturers' specs.

In general, the JM814 is pretty much a direct replacement for OC703 inch for inch. When you're looking to buy, remember that while local is generally cheaper, sometimes the local guy wants a ton more - and local you have to pay sales tax. Just make sure to do all the homework to really compare total costs.

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post #5 of 14 Old 01-29-07, 07:30 PM
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Re: Rock wool vs. Acoustic cotton vs. OC703

My local supplier only carries 1" I believe. When he took me back to where they store it I only saw the 1" 475mf. I'll have to look a little closer next time. This product had 1/2' overlap all around the edges. There was male and female pieces.

John
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post #6 of 14 Old 02-12-07, 04:30 PM
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Re: Rock wool vs. Acoustic cotton vs. OC703

Acoustical Cotton????
Another material to consider?
I'm having a hard enough time finding OC703. Where do you get acoustical cotton?

So, for a 2" or 4" thick 2'x4' absorber, which is the best material?
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post #7 of 14 Old 02-12-07, 08:30 PM
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Re: Rock wool vs. Acoustic cotton vs. OC703

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blownrx7 wrote: View Post

So, for a 2" or 4" thick 2'x4' absorber, which is the best material?
They are all about the same. Mounting and placement are far more important than the material.

When an architect asked me what product to use, I always said the same thing "whatever you think will look good. I will adjust the balance and placement after you pick a product/s"

I like recycled cotton. Its just better for the environment.
post #8 of 14 Old 02-12-07, 09:19 PM
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Re: Rock wool vs. Acoustic cotton vs. OC703

I'd have to respectfully disagree. Each material can be made to work for a certain situation but they're not at all the same.

2" 3.5 lb mineral wool
0.26 0.68 1.14 1.13 1.06 1.07

2" OC703
0.17 0.86 1.14 1.07 1.02 0.98

2" 3lb Acoustical Cotton
0.35 0.94 1.32 1.22 1.06 1.03

However, you are correct that the cotton is the superior product - not just for the environment - but because it performs better. That said, the other products are less expensive and in an application where the superior absorbtion at some of the bands may not be desired based on overall balance, the other materials may be a better choice.

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post #9 of 14 Old 02-13-07, 06:12 AM
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Re: Rock wool vs. Acoustic cotton vs. OC703

Thanks for the responses.
I assume you can obtain Acoutstical cotton from the same insulation supply houses?
TIA
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post #10 of 14 Old 02-13-07, 06:27 AM
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Re: Rock wool vs. Acoustic cotton vs. OC703

No - sorry. Some places can get the 1.5lb Ultra Touch wall insulation which works well for bass control in thickner installations. The 3lb and 6lb cotton is proprietary and pretty much only avaialbe from a few dealers.

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