Here is a test of a few different damping materials that a Allram made. I translated a little from Swedish via Google Translate. You see the graphs in that thread:
"The tested materials are:
*Polyester - Common synthetic cushioning material available cheaply everywhere. Mine was called GAS Polyester, probably bought at BRL a number of years ago.
*Acoustic Wool - Bought recently at Hifikit. Is this what Öhmanites call down jacket lining??
*Wool - Washed, long-fibre sheep's wool, also bought at Hifikit.
*Glass wool- 45 mm in the kind used for wall insulation, among other things
*IKEA Foam mattress - 70 mm(?) honest foam mattress with open
cells. This type has a side that looks like an "egg carton".
*Teijin Twaron - A very expensive material consisting of extremely thin but strong fibers of aramid. The ones that are so thin and light that you go crazy. It flies everywhere and likes to settle in the nose and other troublesome places. Is so incredibly light that it feels funny to hold it. You hold a football-sized lump of damping material in your hand, but it weighs nothing! This material is actually used in woven form as a protective barrier in bullet-proof vests, needle-proof protective gloves, etc., but some audiophiles in the Netherlands tried using it as a damping material in speakers and are raving about the results. I simply had to try it out
An impedance sweep for each material had to show what it managed to achieve. I used a 4 Ohm 12" element in a much too small box, to get as much effect on the resonant frequency changes as possible. All charts have Wool in yellow as a reference.
Empty box: 60.9 Hz Q 1.06
Acoustic Wool: 59.4 Hz Q 0.92
Polyester: 55.8 Hz Q 0.87
Glass wool: 56.7 Hz Q 0.81
Twaron: 55.0 Hz Q 0.84
IKEA: 55.0 Hz Q 0.78
Wool: 55.0 Hz Q 0.78
What conclusions can be drawn from this measurement?
1) You need moff in the box :
2) Polyester is least effective in the midrange and second worst in the bass range.
3) Glass wool is among the best in the middle register but the worst in the bass range
4) IKEA mattress is not very efficient in any frequency range
5) Acoustic Wool has the best damping properties of all regardless of frequency
6) Twaron and Ull both provide very good damping at all frequencies"
