I've been A/B/Cing these 3 cans (HE-500, 4XX, HD-600)
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'nor does it do smoky room jazz quite right'
You're kidding surely ?!?!
Every instrument is tonally just right IMO and can be listened to for hour upon hour especially jazz.
'The 600 is cool and accurate.... clean but cold'
Likewise... half right: accurate but certainly not cold, no chance.
Everyones ears are different, likewise amps (maybe yours, AMP THAT IS, is not the right one ?), also post Eno Roxy cold ?!? The lounge lizard smooth Ferry stuff is much, much warmer and organic, but in no way better, than the early otherworldly more technical, experimental stuff. A world apart (but the opposite of your assertion). Both are superb.
You write far far better than me but I'm sorry have to question yor hearing/opinion. Certainly yours and it seems many others (especially on the HD600 thread where half of the contributors don't actually seem to like the headphones that much ?!?!) seems to be very different to my own experiance.
Each to their own !!!!