Headphones slight channel imbalance

Headphones slight channel imbalance (almost unrecognisable) Please could somebody tell me what is going on.
Hey I am a mixer with a good set of ears, very good hearing and I am able to pick up on the smallest of details and changes; I did the flip test on my Sennheiser HD 600 headphones and noticed sound slightly more pronounced on the left driver by the smallest measure, it is hard to notice.

when I flipped them around I could feel it on the right; telling me it is the left driver that is like this. I swapped around the left and right audio cables going into the drivers and did the same test... same results. So this tells me cables are fine but the drivers seem to be causing this. I have looked after them well only had them a few months... anyway I did the same test on two more pairs of headphones. Two separate pairs of audio-technics ATH-M50x headphones ... The same thing is happening? is this somewhat normal? its VERY slight but more noticeable with vocals.

I have my headphones plugged into my audio interface I was thinking maybe this is causing it. But that wouldn't make sense given I flipped the left and right cables on my Sennheiser HD 600 headphones and had the same thing happening . if the audio interface is sending a slight unbalanced stereo output via headphone jack wouldn't it flip around after testing with left and right cables swapped going into the drivers of the HD 600 headphones?

so I've come to the conclusion that it isn't my ears.. or the audio interface.. but maybe most pairs of headphones have a SLIGHT imbalance leaning slightly more pronounced on the left side. it is genuinely almost unrecognisable but I thought Id do this little test today.

Kind regards,
Joey

 

All manufactured items have a tolerance, so there's no reason why the two should ever be identical, there will always be a difference. How large that difference will be, depends on the tolerances the manufacturer works to. If you're very sensitive to such differences, then you will hear them. With the small number of headphones you've tested, you can't say that headphones have a left-bias, it could just be coincidence. Test 1000 headphones, and you can be much more sure of such a conclusion.

S