1. If you want to be really pedantic (which you clearly do), I wouldn't be measuring the headphone transducers, I'd be measuring the displacement of the microphone diaphragm caused by the longitudinal displacement of air molecules between it and the headphone transducer. [1b] But I think we both knew that
2. I answered this above in reply to castleofargh – curiosity, and I'm looking at ordering cables that have the occasional bad unit so was wondering if this would even have an audible effect.
2.a I was talking about the worst case scenario for what I'm looking at i.e. the worst measured cables in this thread:
https://www.head-fi.org/threads/resistance-of-cables-pics-comments-and-links.907998/, and obviously not a completely broken cable.
2.b [1] I’m well aware that the dB scale is logarithmic.
[2b2] A value of 0.03dB is 33.3 times lower than a value of 1dB.
[2b3] The relative (rather than multiplicative) difference is more useful, which is 0.03dB - 1dB = -0.97dB. I’m not sure where you got your 3400 figure from though. This translates to 0.03dB being 89% of the sound pressure of 1dB (see the ‘Level change Δ Lp => Ratio y for sound pressure’ converter on this page:
http://www.sengpielaudio.com/calculator-levelchange.htm).
[3] Let's leave the pedantry there, because I answered my original question a while ago, and the conclusion is, in some cases, yes, resistance imbalance in real, poorly soldered (but not broken) cables, e.g. the worst ones in the above list, can cause a just audible channel imbalance, but for most cases it won't.