I presume the meter was FIXED on to a stand or tripod, and that the equipment was not changed in setting or other value. I think you said that you ran several iterations of the test to verify results - which would tend to verify them.
One also has to be certain of YOUR physical position at the time you take the measurements, it should be the same (of course, ideally, you wouldn't have to be close to the mic at all.
I'd like to know what the physical geometry of the cables are, both like zip cord? And what speakers and amp are you using? Do you know the impedance and phase plots for it?
The next relatively easy test to make is a gross inductance and gross capacitance check using a DVM that has these functions. Of course slicker methods would be nice, but at least you'll have a first step.
Anyhow the results you find are indicative of either major differences in C & L between these two cables, and perhaps a major interaction with the crossover components in the speakers.
_-_-bear
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