And for those of you who aren't sure if your original HD540 is 300 ohm vs. 600 ohm, even if it's not marked on the outside of your housing, the impedance is stamped into the plastic on the inside of the driver assembly. To see it, remove the earpad and the thin foam layer.
Oh man, thx so much for this information.
It was a pain in the @ss... I needed a torchlight and a magnifying glass. But I can now confirm that:
1) the headband is NOT an "ohm criteria"
2) my HD 540 Ref I are 600 ohms, which I would guess is a pretty rare version of these magical heaphones (I also checked my 540 Ref II and they indeed are "only" 300 ohms).
I guess I finally know why my 540 Ref I are IMO easily superior to my Ref II, Ovation I and Ovation II in terms of timbre, soundstage and imaging,
It may have nothing to do with the impedance, but it seems to be a rather rational explanation. Who knows..?
One thing is sure: that's why they are harder to drive than my Ref II.
This sounds of course childish and nobody gives a shizzle... but I'm now the proud owner of a Sennheiser HD 540 Reference 600 ohms. Who would complain?
I guess I'll at least take advantage of the placebo effect
Edited by Hairspray - 3/4/14 at 4:17pm