From a manual:
Damping Enclosures

Adding damping material, such as lambs’ wool, fiberglass, or Dacron
polyester (pillow stuffing like Poly-Fil) to your subwoofer enclosure
helps cancel any standing waves or resonances that form in the enclosure
because of its particular dimensions. We recommend adding stuffing
only if you need to, and only to sealed enclosures. It won’t make up for a
poorly-constructed enclosure or an enclosure that’s built too small, but it
can help make the enclosure play low frequencies with added emphasis.
It is possible to make your speaker think that it is in a larger box than it
actually is by adding extra damping material, up to 75% of the entire
enclosure volume. The general rule here is to add 1 pound of fill material
(R-19 fiberglass, Dacron, or lamb’s wool) per cubic foot of enclosure
volume.
Naturally, you can vary the amount of fill you use to fit your personal
taste. If you want to gradually change the way a sealed box sounds, add
damping material to the enclosure beginning with about 10% fill, and
adding up to 75% of the total enclosure volume according to the way
you want the enclosure to sound. Don’t compress the material, just
loosely add fill to the enclosure. This works because the fibers of the
material cause the sound waves to bend around them, slowing the waves
down and taking longer to reach the enclosure’s sides. As much as a 15%
change in box volume/response can be achieved by this method.

Flores

 

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