The Q550's have limitations in full range with bass heavy music at loud volumes.
I discovered this with my Q750 but crossed over with a subwoofer it's not an issue(they can be pushed to ear bleeding levels with a sub).
The problem with bass heavy (extreme) songs is the uni-q will "chuff" between the woofer/tweeter since the UNI-Q is sealed within the cabinet air has no where else to move.
a part from this minor issue(which never happens in 99% of situations) I love them