John, I will admit I don't know all the fancy formula's since I hold no electronics degree of any sort, though I do mess around a bit building speakers and crossovers. I purchased a Dayton Audio test system, with this, I can take many measurements of raw drivers etc. It also allows me to take an impedance frequency sweep . I took 3 different sweeps, one of the tweeter/mids, one of the woofers and another of all the drivers. I include a screen shot of all three purely for reference purposes.
Sorry you may have to save the pic and open it with paint. Its a screen capture.
It seems clear to me that 2 separate amplifiers will each see an entirely different impedance when bi-amped (bars removed) than will be seen by a single amp (jumper bar in) .
None of this really matters imho since bi-amping or bi-wireing passively is for all intents and purposes of no use.