Bernard, did you ever resolve your headphone issue?
I have the exact same problem with the same pair, only I have two headphones, one is a HD414 and the second is a JVC pair,both are faulty
and have been told by Sennheiser that the 2k driver unit I need are obsolete.
so I am trying to make one working one out of the bits of the two headphones, all I need is to swap your faulty HD414 driver with my working one, a straight swap!!
what do you say?
(p.s. it MUST be the black HD414 and not the grey one)