There has never been a speaker that has shown any audible difference under any real world test circumstances to make any difference at all... ever.
Hhmmm; I guess BMX is pretty old since he obviously has tested every speaker ever made under every possible set of conditions!
Seriously; bi-wiring CAN make a difference if done correctly. The effectiveness of bi-wiring has nothing to do with cable size but all to with intermodulation distortion. The strong magnetic field generated by the low frequency current in the cable interacts with delicate magnetic field generated by the high frequency current in the cable. This interaction causes distortion.
Bi-wiring mitigates or eliminates this distortion by separating the low frequency conductor from the high frequency conductor. The key word is separate. It's of no value to run the two cables bundled together (even though this is what 50 percent or more of audiophiles do).
To make bi-wiring effective the two cables need to be separated by a few inches. If you haven't bi-wired with separate cables, you haven't bi-wired.
My two cents!!
Russ (BSEE, MSEE)