- 585 Posts. Joined 3/2005
- Location: NY
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The purpose of the mineral wool is to absorb some of the sound waves in the cups so that they don't bounce around so much. Mineral wool is one of the best materials for this purpose, but you can also try acoustic cotton, acoustic foam, and compressed fiberglass (just be careful with that stuff). You can also try to use thicker slices than what Stax uses.
I would just try a bag of cotton balls from the drug store. Kind of pull them apart a little bit and they mesh together nicely. I thought they made the sound good in past experiments and doesn't have the downside of other materials.
I read on here before from one of the top stax guys that they soaked mineral wool in alcohol or water I forget to get the junk out of it. Let it dry out then installed it. Sounded like a really good idea to me. I would still try the cotton balls once. It was quite a while ago but I thought I got the best sound from it. It was interesting how it could be layered denser then a bit softer. Mostly felt like I could get a bit more treble and still keep the bass. Cutting down on reflections but I could be missing the whole point of the Sigmas.