Tried that "Using Sound Signatures" feature of autoeq.py, the result is not satisfying.Hey Duke, thank you so much for your reply.
I see this is Parametric EQ settings for HD650 to Harman Target (from AutoEQ, with measurements from Oratory1990).
I was wondering If I could make 660s sound similar to what 650 did after equalizedwill try to figure it out.
My main problem with 660s is that it sounds not smooth enough, sometimes the high frequency sounds like broken glass... And overall the bass sounds strange.
Update: just find out I can use autoeq.py to make a headphone sound like another. Will try it tomorrow.
Good news is, I reinstalled the earpads of 650 and two channels are now balanced. Still can't choose between 650 and 660S cause after more listening, I feel like they have both advantages and disadvantages.