If this is off topic then ignore me ....

Has anyone here done any form of testing with balanced/unbalanced cables. I dared to mention once that I fancied trying a different way of cabling the headphones and almost got laughed off the forum. (Don't laugh)

Is there anything in headphone response that shows any benefits to a recabling with separate plugs for each side?

Haven't tested but my view is this:
When a HP is connected to a bridged amplifier that has a 'considerable' output resistance (>10 Ohm) there could be sonic effects due to voltage division as the output resistance doubles.
Another, technical reason, that is most appear-ant in low impedance headphones is the fact that both drivers are fed with their OWN wires (4 wires in total) where as when fed with a common 'return' wire there simply is a measurable crosstalk.
When a headphone is wired dual entry (so with 4 wires) and the 'return' wires are connected in the plug I can't see much benefits of balanced drive unless one needs the extra power as the voltage doubles (and thus the power quadruples) if that is needed.

Maybe Purrin (if he has the time and is interested) can do similar measurements as done with the HE500 on different amps, but this time balanced and unbalanced
(SPL level matched) this would answer this often asked question.
Can't do this myself, measuring rig almost finished but no balanced HP's not amps.

The measurements will all be the same. Seriously. I've done enough comparisons with different amps to see. As long as the amps are reasonably linear and are close enough in output impedance, the headphone measurements will be identical.

Aha. That's what I've heard as well. It's these claims of low level crosstalk being cut with no proof that I have wondered about.

The measurements will all be the same. Seriously. I've done enough comparisons with different amps to see. As long as the amps are reasonably linear and are close enough in output impedance, the headphone measurements will be identical.

Agreed when both channels are driven at the same time (or at least have been fed the whole spectrum at full power).
3 wire cables will show (low level) crosstalk in the other channel when only 1 channel is driven.
The amplitude of this will depend on: wire resistance, HP driver impedance.
In any case it won't show in normal FR/CSD measurements at all.
The audibility of this would thus be harder to determine (in an objective matter) but as it is linear (cables simply do not add non-linear distortion) it might only influence stereo image slightly on those old L-R beatles alike recordings or show very small level differences.

The theory behind is in this article:
http://www.mediafire.com/view/?82kf0r5kdckdcer
page 7 and 8

You'd need some crossovers causing weird impedance shape for any impedance to matter - high min/max spread. Or a balanced armature.

About crosstalk, it will also influence the resolution somewhat - cross-channel IMD is worse when there's high crosstalk. So the effect of it would be more audible on worse amps more.
I find the -15 dB vs -30 dB vs -60 dB crosstalk quite audible and easy to discern, with e.g. -15 dB vs -23 dB is about as easy to discern as -30 dB vs -45 dB - pretty hard. Increasing differentiation threshold, so to speak - only dramatic differences are really distinguishable.