Again, ''all else being equal'' M.H. if Sennheiser would use a 50mm driver, instead of 56mm, the treble would probably be, that much hotter.
As I always say, when you get to this level, there is no ''i''mproved or ''e''volution, for me, it's all ''d''ifferent, And let's not forget, our respective upstream equipement is also different. So if my old PS1000 had an ideal synergy with my sound system. it's not surprising that I ended up preferring them, to the e serie.
I believe that manufaturers have to stir things up every few years, if they don't, they'll be accused of resting on their laurels. I mean, do we really need a cable the size of a garden hose, to feed 2'' speakers.
Take the HP1000 for example,, they are still viewed by many as THE best headphones that Grado has ever made, and they're over 20 years old now. And for others, it's the first gen, buttoned RS1. It just goes to show...