I have a pair of Sennheiser HD 540 reference II headphones that are starting to fail me (I believe it is the contact springs) so I am in the market for something open backed to replace them. My problem is that I can't really find a frequency response curve of the HD540 II's to compare them to other headphones I have looked at; the closest I can find is this GoldenEars review of the HD540 reference gold (which I believe has a similar sound, except for less bass):
However, as these HD540 II's are over 20 years old I have had to do some things to them that have probably changed the sound signature, like replacing the stock velour earpads with spare SRH 840 earpads (which worked surprisingly well), as well as making custom paper baffle covers to replace the original ones that came off.
As far as I can tell, the sound of the HD540 II's that I have is mostly neutral, with some sort of treble emphasis. I think it is around 4-6 kHz, but again I can't really be sure. I also have a pair of Shure SRH 840's which apparently have a peak above that and a dip around 5Khz, and the treble peak on the 540s definitely seems to be lower than that of the 840s. This makes the 540s render things like cymbals, violins, and pianos far more realistically than the SRH 840s, and I would ideally like to find another headphone that can do this. While the SRH 840 treble sounds a bit "thin" because of the upper treble emphasis, the HD540 treble sounds much more substantial. Basically, I want treble with a lot of detail, but without sibilance and with a realistic sound.
In terms of the rest of the frequency range I am looking for flatness with bass that is present, but not emphasized. I would like to get as much bass extension as I can, but I realize that open ear headphones are often weak in that department. One other major consideration is comfort; I hate headphones with shallow earcups that have the driver rest on your ear, so I want a pair that completely surrounds my ear without touching it.
I have been looking at the AKG K702, K712, Beyerdynamic DT880 and DT990, Sennheiser HD600, Shure SRH 1840 and some others but without actually listening to them I have no idea if they have the sound I want (since going based on frequency response curves isn't all that reliable). I will mostly be using these with an E07K.
Thanks in advance!