Awesome review!

Definitely agree with your praise of the Stax founder. He made a great phone as we say "by guess and by golly." Re the mineral wool and enclosure. The Stax drivers are unusable in the Sigma configuration without the enclosure and wool. They give virtually no bass when sitting in open air, unlike for example the AKG K1000. On the other hand if you seal the enclosures as I once did with duct tape, you get an impossibly boomy sound. Somehow Stax got it just right with the enclosure and mineral wool., decent bass without too much boom. Still a bit boomy though, probably why they make good rock phones.