I did my modifications about a year ago to some 125's a buddy had and hated so he gave them to me, way back we used to giveaway any extra stuff we had and didn't need so a bunch of us got the little stuff for free and Big Bill had a friend who made leather headbands for us and my mods still sound good today and I'll never sell them because the stories behind all the changes are incredible:
the shells are made from Limba wood, leather headband, and household screen. I did a bunch of experimenting with different materials right behind the screen on the cups- thin foam was the best. Tightened up the bass while still allowing the air flow for the high end bits. I use these as much as my HE-5LE's...different type sound, both sound great to me.......total cost was like $70 to mod these freebies!!!!