So I have no idea what I'm doing, but decided to make my grado sr80e's closed back. Long story short, I put some acoustic dampening stuff in their, one cottonball in each earcup, quarter modded pads, and wrapped the pads in electrical tape. Not the best isolation, but better than before, and still not bad. Will write up more in the morning, but heres the measurements after a few hours of work. Unmodded and modded, just FR, will get others tomorrow. Not bad, just need to better match channels.