^ psychoacoustics are a real thing.
Everyone's taste and headphone-upgrade path is different, I feel a little unique from other people that have recently come to the HD700 in that I haven't heard any other Senns besides the PX100 and HD202, and my head-fi journey has mostly been neutral or erring on the side of bright, starting with the rather very flat Etymotic ER•6i. As befitting a hearing aid company that transitioned to making the first IEMs, the ER•6i didn't have the most treble extension but the FreqResponse is markedly close to neutral (broad and modestly elevated bass) compared to most consumer headphones. After that, for years I used pretty balanced or bright-tilted headphones, the DT880 was a little too bright-tilted for me but coming to the HD700, the latter is not too bright. I firmly believe that if I'd spent a fair amount of time adjusting to the HD650 an appreciating the merits of that, I would have a tough time re-adjusting to the HD700, it would seem weird.
Now, I have an even more unique situation where shortly before getting the HD700 I picked up a used pair of Stax SR-X, which I demoed once or twice to Wow results two or three times in my basement, but I was sourcing from my iPod's Line-Out dock and it's cold down there so I never spent much time spoiling myself with it. I have been using my HD700 almost exclusively since getting it with my tube amp (some nice rocket-logo tubes plugged in), and I think I've adjusted to it. Once you use the HD700, the lasting impression that doesn't fade away is the wearing comfort! Anyway, I finally got a Sound Blaster X7, and now have a convenient way to A/B my dynamic and electrostatic headphones. The Stax really really deserve their sound quality praise, I haven't seen any frequency charts but the curve would be gentle with loads of treble extension, for me it's got more technical and WOW! chops than the HD700 and may spoil me in the future, but the HD700 is without fuss easily the more comfortable to wear. Switching back to the HD700 was interesting because in contrast it was immediately clear that the treble was actually overall not as forward and the bass a tad bit warmer, with a spot in the treble near cymbals where suddenly the treble is forward... but after a few hours, even switching between the two headphones the differences seemed to become less prominent. Now, the Stax is still a bit more reference, but I'm still happy to share head-time with the HD700 for it's comfort, especially while gaming.