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| Re: Insulation inside of speaker: Spray Foam? [message #71608 is a reply to message #71606] |
Wed, 29 February 2012 23:42   |
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Wayne Parham
Messages: 18786
Registered: January 2001
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Illuminati (33rd Degree) |
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We're talking about three different things here.
First, R13 is a fiberous material, not an open cell or closed cell foam. It's best at midrange and high frequency attenuation, which is exactly what we want for damping inside loudspeakers.
Second, open cell foam is kind of like the foam used for grille materials. Sound passes through it, but it forms a mesh of fibers when the cell walls break, hence the name "open cell". So it does attenuate sound, especially when thick.
Third, closed cell foam (like what's in those cans) is a foam that makes little bubbles that never pop. The surface is essentially solid, sort of like rubber. It's acoustically reflective, and won't absorb much at all. It can be used as the damping layer of a constrained layer panel, but by itself, it reflects much more than it absorbs.
I'd characterize fiberglass insulation as acting primarily as an absorber of sound, and almost completely ineffective as a reflector or barrier of sound. Closed cell foam is just the opposite, mostly a reflector/barrier but not very absorbent. Open cell foam is somewhere in between.
One thing to keep in mind is the insulation in walls is there to provide both a sound barrier and a thermal barrier. So there is more to consider than just acoustics. Even so, from an acoustics standpoint, the walls and the insulation are both barrier (reflector) and damper (absorber). Some of the goals are the same or at least similar, but some are very different.
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| Re: Insulation inside of speaker: Spray Foam? [message #76248 is a reply to message #76246] |
Tue, 09 April 2013 11:00 |
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Wayne Parham
Messages: 18786
Registered: January 2001
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Illuminati (33rd Degree) |
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I don't think it will work as well. If you have a specific material you want to try, you could certainly test it to be sure. But I have found poly fibers I tested to be pretty ineffective. Same with organics like cotton. Both seem to act more like a solid mass, less like a damper.
I also think in terms of health, fiberglass insulation is often maligned unreasonably. This is probably because it looks similar to asbestos, which is harmful. But fiberglass is not, it is completely benign, and is probably the safest stuff you can use.
I mean, I know it is irritating to install it, because it makes you itch. But it is only irritating when it is disturbed, when your skin brushes against it. Once it is installed, it settles does and does not give off fibers into the environment. Sound energy isn't enough to break the fibers loose, so they do not enter the air.
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