How does bi-wiring work?

Biwiring is nonsense. It does nothing but might cause a phase/time issue.....BiAMPing is a huge improvement to many speakers with a good crossover BEFORE the amplifiers. That is truly what the four terminals should be referenced for.

Part of the cost/performance bi-wire "argument" is that the higher frequencies do not require as much gauge as the lower end.  Therefore, put less of the "good stuff" (i.e. better material) on the top end thus extracting the best sonics from those materials, and bulk up (add meat) to the bottom end with less expensive materials to get more gauge.  This optimizes the cable budget using the most cost effective materials where they'll yield the best sonic benefit(s).

How in God's name can a single amplifier put the highs on one wire and the lows on another? And if it could, would not different gauge wire cause all kinds of phase/timing issues......(I know at the frequencies of HiFi audio this really doesn't matter...)

That: "NOTE: bi-amping is a different story". VERY different. 

@rbertalotto …”Biwiring is nonsense.”

Just out of curiosity. What bi-wiring configurations have you tried and what were the system components?

I used to have a Cardas bi-wired Golden Cross cables with my ESS AMT 1D speakers with a Threshold 500s amp and Threshold T2 preamp. The Cardas sounded much better because of the warm nature of the cables. I was not making much money and there was no way I could get a non biwired set to test.

I’ve used doubled up Audioquest Type 8, and then Audioquest Gibraltar where there is “optimization” for high and low frequencies. 
 

Many people I know who understand far more than I do about electronics and noise (including a physicist who was PM of the first LIGO construction) say that biwiring should not make a difference. But, like so many things in audio, it does, at least to my ears. I have done the experiment enough times that I have convinced myself, and Bill Low certainly agrees.
 

My formal electronics training was taking and auditing a year of electrical engineering for mechanical engineers at UC Berkeley (I was a grad student in Geology helping to build some lab measurement systems), taking a bunch of BS Physics major courses and labs as an undergrad, and have experience helping design and build laboratory equipment used on the JOIDES Resolution scientific drill ship and in other geology and chemistry labs. I’ve also built and modified audio equipment earlier in my life. Oh yeah, Thevanin equivalent, now I remember!