Originally Posted by einsteinjb
Hang on. Let's be clear -- there's arguably no advantage to bi-WIRING as it does nothing except double the effective gauge of the wires. If you're already using 14 or 12 gauge, you'll never hear the difference.
Bi-AMPING might not truly double the power to your speakers but there is an advantage. It gives you extra headroom because assuming you're running say, 300 watts/channel @ 4 ohm amp channels (x 4, 2 per speaker), you'll now have a full 300 watts available to each bass section and another full 300 watts/channel available to each tweeter section, rather than one 300 watt channel having to cover both. While the tweeters will almost definitely never need that kind of power, bass can suck up power on transients so separating the two can reduce potential distortion and allow the speakers to play more cleanly at higher volumes.
As for wiring, nothing special is required. Just run two sets of oxygen free copper wiring, 14 gauge or better yet 12, and you'll be fine.
While that is possible it depends on the speaker of course. Tweeters almost never need to use much power at all. So it may be something like the woofer seeing 250 watts of power with the tweeter using 50 watts vs. the woofer seeing 300 watts and the tweeter seeing 300 watts. These are hypothetical numbers, but the difference between 250 watts and 300 watts is not that much added headroom for the woofer.
I think the real benefit to biamplification is when you disconnect the internal passive crossover and utilize an external active crossover along with the two amps.
In my experience, the tweeter uses so little power that the woofer does not gain much headroom in a passive bi-amplified setup. Your experience could be different, however, and I don't doubt the possibility of a speaker existing that would benefit more for a passive bi-amplified setup.
I have, however, noticed an increase in headroom when supplying 1 amp, but with double the power (as you might expect). Bridging an amp also yields a similar result at the expense of the distortion from both channels adding together (usually not a problem for the amps I have used). If the amp has decent distortion figures, I would bridge two channels together if I had that option rather than bi-amplification of the speakers (unless an external active crossover was used).