QPAD QH-85 Review @ Vortez
 

The primary difference that will affect people’s choice between the QH-90 and QH-85 is that the former is closed backed and the latter is open. What that means is, literally, a closed back is sealed, reducing sound leakage going in or out, where an open earcup will leak just as much sound out as it pumps into your ears. There are advantages to using an open back of which some may prefer, such as creating a much more natural 'airy' experience with a larger 'out of head' soundstage with more detailed high tones at a trade-off of losing some bass impact.

http://www.vortez.net/review.php?id=867