There's a kinda new speaker cabinet blanket on the market, I don't know it's name.
It's a very fluffy cottony material that must be in a gauze like net. Without it, the fluff blows all over. It "absorbs" better than the usual stuff.
Better designed cabinets don't "need" that much insulation in them. It's function is to "trick" the woofer into thinking the cabinet has a larger volume than it does. This is all done through the thermal expansion of air under pressure and the thermal absorption abilities of insulating materials.