Mike, I didn't really follow the "negating" supposition, but an external crossover(usually electronic)has to be placed prior to the amplifiers so that each amplifier only gets an input of the desired frequency range. Once that is done and the crossover is taken care of, the internal crossover in the speaker has to be removed or at least bypassed by rewiring so that the signals from each set of speaker terminals go straight through to the appropriate driver. Very few home users actually have gone to the trouble of bi-amping, which as Alan has pointed out is of more significant benefit in professional applications involving mega-wattage.
