Great review bpandbass. These headphones are real gems. I in particular adore the treble presentation which I had never come across with my HD595s which were quite dark sounding. About the midrange you say "This isn't a mid-forward headphone." which I agree with, but on-line there are so many who think these are mid-forward headphones. Presumably this comes from previous ownership of 'V' shaped frequency responses with recessed mids that make them think this. I think the mid-range is as balanced as the bass and treble. Interesting what you say about the sub-bass, I have never found a frequency response curve for the HD580. The HD600/650 have limited bass extension compared with modern high grade headphones. A truly remarkable set of headphones it's a pity Sennheiser no longer make these.

I say mid-forward relative to the HD650, simply because the HD650 has a boosted upper bass and rolled lower treble. The HD580 sounds remarkably balanced to me. I've owned the AKG K612 and I can say that aside from maybe a since of a little more detail and deeper extending bass, the HD580 trumps the K612 in neutrality, and it doesn't have that annoying 2khz peak. The 580 isn't blarey in the upper midrange compared to the Q701. I originally thought the HD580 was sibilant and blarey because it wasn't sealing against my ears well with a brand new pair of earpads. With a pair of broken in pads it was night and day better.

It's really sad Senn doesn't seem to care about making balanced headphones like this. The HD700 is a strange amalgamation of brightness and warmth. Not a true successor to the 600/650/580, and it is overpriced. Comfort looks excellent though. I'd like to see Senn overhaul the HD600 and HD650 and give them better sub bass extension and deeper earcups. I'd like to see memory foam like the AKG K712.