[thejammonster]

Not looking to argue, and I realize Massdrop says closed, but they're "semi-closed." I own them and can confirm the earcups are the same design as my semi-closed TH-600. They don't leak sound like an open back but I can't recommend them for someone looking at strictly closed back.

http://www.head-fi.org/t/788776/fostex-x-massdrop-th-x00-review

"Fostex x Massdrop TH-X00 semi-closed around-the-ear headphone
Fostex TH-900 semi-closed around-the-ear headphone
Fostex TH-600 semi-closed around-the-ear headphone
Fostex T40RP Mk3 closed around-the-ear headphone
Fostex T50RP Mk3 semi-closed around-the-ear headphone
Fostex T50RP Mk2 semi-closed around-the-ear headphone"

 

[OMGLadyGaga]

Ya he's right, if they're anything like my denons and the fostex models they were based on, then they are basically open

 

[Music Alchemist]

Not looking to argue, and I realize Massdrop says closed, but they're "semi-closed." I own them and can confirm the earcups are the same design as my semi-closed TH-600. They don't leak sound like an open back but I can't recommend them for someone looking at strictly closed back.

 
Good point. In retrospect I shouldn't have mentioned those Fostex models since isolation was the goal.

 

[NA Blur]

Huh, the pair I had at a meet were perfectly sealed so I wonder if it is a pad issue because it looked like the ones I auditioned had these pads:
 
I will check into what pads were on the pair I tried because they were super sealed.