AVS Forum banner
Status
Not open for further replies.
1 - 14 of 14 Posts

·
Registered
Joined
·
252 Posts
Discussion Starter · #1 ·
While in the process of building my dedicated HT, Larry Chanin gave me a piece of Linacoustics. It looks like dense fiberglass with a black "tar" coating on one side.


My question is using Owens Corning 703 rigid fiberglass as a substitute for Linacoustics. Is the usual and customary 703 the version without FRK (foil reinforced Kraft Paper) on any side?

Take Aim
 

·
Registered
Joined
·
7,655 Posts
Linacoustic and 703 will react differently. If you're doing the 'bottom of the wall all around' thing, 703 faced or unfaced would likely be too much in some areas.
 

·
Registered
Joined
·
2,818 Posts
I'd disagree...if I recall 703 and Linacoustics are very similar in acoutical properties. I'll have to find it, but someone posted a link to a site that listed all the products and their absorption rates. I went with 703 instead of linacoustic for that very reason.


EDIT - Found it. http://www.bobgolds.com/AbsorptionCoefficients.htm


As you can see 703 and Linacoustic are similar. If you go with 703, you can get foil faced or plain. Install it with the foil against the wall. I got unfaced as it was a bit cheaper and used spray adhesive to attach it to the walls. (check out bottom of page 4 at my site)


703, plain 1" (25mm) 0.11 0.28 0.68 0.90 0.93 0.96 0.70

Linacoustic RC 1" (25mm) 0.08 0.31 0.64 0.84 0.97 1.03 0.70
 

·
Registered
Joined
·
3,639 Posts
The Permacote on Linacoustic is there to keep the fiberglass in place. It's used in air ducts so it's safe to use in the room. There has been some talk about fiberglass getting out through the weave in GOM and into the room when used unfaced fiberglass. OC 703 seems pretty dense so it might be alright.


I chose the Linacoustic because of the permacote and because it is so easy to cut since it comes in a big roll. And you can just use a few staples to hold the fiberglass in place until the fabric is up.
 

·
Registered
Joined
·
7,655 Posts
If I'm not mistaken, those numbers for the Linacoustic is for the facing away from the sound source. When mounted with the facing toward the room, the HF absorbtion goes down - hence my comments about 703 being too much for almost half the wall surfaces.
 

·
Registered
Joined
·
3,258 Posts
Take Aim,


I consider the two acoustically interchangeable. Both are 2.5-3 lb density fiberglass.


The manufacturers absorption coefficients for 1" material, at standard octave band absorption from 125 to 4 kHz, are:


0.11 0.28 0.68 0.90 0.93 0.96 for OC 703

0.08 0.31 0.64 0.84 0.97 1.03 for Linacoustic RC


Measured reverberation room absorption coefficients can vary quite a bit. According to the ASTM spec for reverberation room measurement of type A (flat) mounting, this absolute difference, for the identical sample measured at the standard octave frequencies at different laboratories (to a probability of 95%) is:


0.14 0.18 0.12 0.10 0.10 0.13


Yes, the error really is that big! :)


The major difference for these products is usage. If you need rigid board, and are willing to pay extra for it, go with the 703. Otherwise, Linacoustic is a more economical choice.


And the 703 I'm referred to is without any facing. Either FRK or ASJ facing outward will reduce high frequency absorption.


Regards,

Terry
 

·
Registered
Joined
·
252 Posts
Discussion Starter · #7 ·
Terry,

Owens Corning 703 can come with FRK (foil reinforced Kraft paper) and ASJ. What is ASJ? I can't find the definition even on the OC website.

Take Aim
 

·
Registered
Joined
·
3,258 Posts
ASJ stands for All Service Jacket, and is a type of vapor retardant facing which has a bleached (white) kraft paper surface.


- Terry
 

·
Registered
Joined
·
2,818 Posts
Quote:
Originally Posted by Terry Montlick
The major difference for these products is usage. If you need rigid board, and are willing to pay extra for it, go with the 703. Otherwise, Linacoustic is a more economical choice.
Again, I'd disagree. The 703 for me was most economical because the smallest roll of Linacoustic was 100ft. I needed 136 ft. Buying a 2nd roll for 36ft would've been a lot of waste. In the end, I only had four 703 panels left.
 

·
Registered
Joined
·
7,655 Posts
Terry,


Are you saying that the Linacoustic mounted with the barrier toward the room is still up around .9 at 2k and 4k? I was always told that those numbers were for it mounted the other way.


If it really is as you say, then when using Linacoustic on the bottom of all the walls and batting on all of the top of the walls, don't you end up with a ridiculously overdead room in the highs? Just doing some very quick calcs on a couple different room sizes shows that it's way too dead.
 

·
Registered
Joined
·
3,258 Posts
bpape,


My understanding is that the mounting of the Linacoustic for reverberation room testing is with the coating facing toward the sound, as it would be for its intended use as a duct liner.


ASTM C 423 – 02 specifies that "Insofar as its acoustical properties are concerned, the specimen shall be mounted in a way that simulates actual installation."


I've never tested this myself, but trust that Johns Manville is conforming to the ASTM standard.


Regards,

Terry
 

·
Registered
Joined
·
7,655 Posts
Hmmmm.


Logically, that would mean that the barrier is air permeable enough to allow the highs to pass through and be absorbed. Contrarily, in order to perform in a high airflow enviorment like ductwork where the idea is to keep any of the fibers from being carried through the house by the airstream would indicate it is not permeable.


Quite the conundrum.
 

·
Registered
Joined
·
3,639 Posts
It can be permeable and still hold back the fibers in a high airflow environment. Look at the permacote on Linacoustic. Now, the 703 might be a different story. Maybe it reflects a lot above the 4000Hz range and absorbs well below that frequency.
 

·
Registered
Joined
·
6,697 Posts
Quote:
Originally Posted by takeaim
While in the process of building my dedicated HT, Larry Chanin gave me a piece of Linacoustics. It looks like dense fiberglass with a black "tar" coating on one side.


My question is using Owens Corning 703 rigid fiberglass as a substitute for Linacoustics. Is the usual and customary 703 the version without FRK (foil reinforced Kraft Paper) on any side?

Take Aim
Hi All,


Sorry I'm late, I just discovered this thread.


This probably won't change any of the discussion, but in the interests of accuracy the sample I gave Jim (takeaim) was 1" Coated Insul-SHIELD Black, not Linacoustic.


1" Coated I/S Black 0.09 0.29 0.67 0.89 1.03 0.99 NRC = .70


Larry
 
1 - 14 of 14 Posts
Status
Not open for further replies.
Top