My Sennheiser HD600 L/R discrepancies in frequency response

[vertumno]

Hello,
I'm going through a whole testing/evaluation/calibration of my studio and it would seem that one of the more puzzling mysteries is the different frequency response of my HD600 between Left and Right channel, they sound different, namely in the low frequency domain (around 80Hz) one sounds louder than the other (also different, but that might be just the loudness).

At first I thought it was my ears but a quick ear cups swap told me it wasn't.

Then I thought it was my audio interface, but I swapped for a brand new Motu M2 I have and problem was still there, so I concluded it's the headphones.

I never noticed it before but then again I never tested them at this length, and if panned centre low frequencies sound ok, is it to be expected that they sound different (just like speakers do) or are they busted?

 

[solderdude]

Here is a HD600 I measured (2015) that appears to have some difference in bass extension.
Never seen it this 'bad' in other (Sennheiser) models.

 

[vertumno]

Thank you that’s a great resource.

I cannot measure it like you did unfortunately, but it seems to mirror what I’m empirically assuming with my hearing, Left channel louder than Right channel, perhaps with an even more pronounced difference.