Chuckle...
Crinacle's graph isn't even matched at 2300Hz
It's a comparison between two set of cans measured with the same methodology. So for this methodology / set of measurement conditions, the 660s are slightly more emphasized between ~100 to 2000Hz as compared to the HD650s.
Other differences between the two are evident as well but the broader point is that measurements can vary depending on the setup and it's the comparison that matters.
More importantly a blanket declarative statement such as "The end. HD650 is better in every way." seems to assume that we all hear the same (physically and psycho-acoustically) which is a false assumption.
That said, glad you like the HD650s so much.
I do as well! In fact, they're the only set of cans I've repurchased because I got rid of them when clearing out some Senns and Beyers along with an OTL amp. Glad I got a second set and won't make that mistake again.
Even so, I still choose the 660s over the 650s...sometimes -- and vice versa!