How does bi-wiring work?

It was cheap and easy for me to try. and thought it might offer some benefit, so I did it. Never compared single wire since. At worst, I doubled the wire gauge and added minor wire cost....at best, it sounds wonderful so I leave it as-is and enjoy the hell out of it. 😎

+1, @knotscott  , that is kind of the way I look at it.

It doesn’t work any different than non bi-wired. From an electrical engineering standpoint, the amplifier terminal and the two speaker terminals are the exact same node. The only advantage IMO of bi-wiring is that the sonic signature of a speaker can be customized by inserting resistors between the the high and low terminals. This adds additional nodes between the amp and the crossovers and changes the filter parameters (that is, it's designed that way -- you shouldn't do that yourself).

Actually the, filter if well designed like for example a Vandersteen ( passing Electrical Engineering since 1977 ) will back the crossover point ALL the  way to the amplifier. Like i said, the basic physics are well understood…. 

I have identical single and shotgun bi-wire versions of the same cable and marginally prefer the shotgun bi-wire so that’s what I use.  I attribute the difference to basically doubling the gauge of the cable that significantly reduces resistance.  In the end I don’t care why, I just know it sounds better.  But, and this is significant, the difference is subtle enough that I’d upgrade all upstream electronics first before I’d consider going to a shotgun bi-wire cable because I think you get potentially bigger improvements there.  But, if you feel like you’ve got all that sorted I think bi-wiring is at least worth trying.  A more significant improvement occurred when I used banana jumpers in addition to my shotgun bi-wire spade cables.  Using both together significantly tightened up the bass and improved imaging and I won’t listen without the jumpers.  Don’t know why it works, but it definitely does and a cheap tweak so well worth trying IME.