Whereas when I put on the old Sony phones a few days ago for the first time in a long long while and went "fewugh!"...
I find the brand new 650's to be very similar to the stereo, they are speaking with the same voice... same voice but in a very different (dead) acoustic.
Headphones on, bring up the speakers, the speakers just eventually take over, without any major change in tone.
There may be an extra hint of clarity/twang from the speakers (electrostats), but I'm not disappointed.
The biggest difference is in the soundstage, not accustomed to having the players on my sides as opposed to in front and echoing around me.
Overall tonal quality and balance seems just fine, and a good match for the rest of the rig.
Now to let them sit on the coffee table and let them simmer on low for a while.
I'll check back much later...
*a little zinginess I thought I was absent earlier (bluegrass banjo) seems to be emerging now, with 4 hours on them (Pink Floyd - Division Bell)