I listen at lower to moderately low levels so I may not have flexed the diaphragms significantly. For me, the PM-1's big draw is the top to bottom cohesiveness and sense of a solid whole, not a connect-the-dots combining of the parts of the frequency range. The treble enhances the natural timbre of the midrange without singling itself out or calling attention to itself by jumping out from behind the mids and shouting "I'm here!". You are not focusing on what the bass, midrange and treble are doing because they are of a piece.....which is what music is, right? So if you want a breakdown of bass/mid/treble, you'll have to send me another headphone that sells bass/mid/treble separately.
I have read some comments about the PM-1 sounding closed-in or not very spacious. This is nonsense. If the recording has a sense of space, it is perfectly reproduced as such via the PM-1....try "Moon" by Foals or the bonus remix of "Flesh and Bone" by The Killers....the sound extends well outside the head and ears.
Add to that the sumptuous comfort and you have a set of phones you could listen to and enjoy music with indefinitely.