There is some theoretical effect (could be improvement or degradation) due to bi-wiring. It relates to the small signal that exists at the common (-) terminal of the speaker as a result of the impedance of the speaker wire. If you don't bi-wire, the tweeter signal is referenced to the voltage at the low end of the woofer, which may be slightly different from the voltage (ground) at the amp. Because the woofer is a complex load (not purely resistive) this error signal is not just an attenuated version of the music signal.
All this is just theory, but it is the only scientific reason that I have found to suggest that bi-wire has any effect at all. Note that it suggests that only the return wire (-) needs to be doubled up, and also that use of very heavy wire will eliminate the effect (resistance goes to zero). In fact, this effect may explain why heavy wire sounds better for a mono-wire connection.
If one were to experiment with bi-wire, I suggest that you use very small wire (say #30) so as to aggravate the effect (when mono-wired) enough to be clearly heard.
PS: My Maggies are bi-wired. It was an experiment, using #24 wire for the tweeter so as to replace the 1 ohm tweeter padding resistor with cable resistance. It's hard to say if there was an improvement, but certainly no degradation so I have left these wires in place.
All this is just theory, but it is the only scientific reason that I have found to suggest that bi-wire has any effect at all. Note that it suggests that only the return wire (-) needs to be doubled up, and also that use of very heavy wire will eliminate the effect (resistance goes to zero). In fact, this effect may explain why heavy wire sounds better for a mono-wire connection.
If one were to experiment with bi-wire, I suggest that you use very small wire (say #30) so as to aggravate the effect (when mono-wired) enough to be clearly heard.
PS: My Maggies are bi-wired. It was an experiment, using #24 wire for the tweeter so as to replace the 1 ohm tweeter padding resistor with cable resistance. It's hard to say if there was an improvement, but certainly no degradation so I have left these wires in place.