Wiki is a good place to start and the reference links seemed unbiased.
http://en.wikipedia.org/wiki/Audio_crossover
Never understood the "time and phase coherent" argument myself when one side is 90 degrees out of phase and all the other positioning and design issues. I wouldn't presume to argue with Dunlavy and Thiel and I've heard their remarkable results but I've also heard enough to know that a complex question deserves more than simple dogma. The simplest is to keep the xovers beyond the vocal frequency range, where our ears are most sensitive and wherever those lines are drawn, but that's rarely practical and involves other compromises.
Inductors are probably the worst offenders in passive xovers and they get correspondingly bigger for lower frequency, low pass filters.
http://en.wikipedia.org/wiki/Audio_crossover
Never understood the "time and phase coherent" argument myself when one side is 90 degrees out of phase and all the other positioning and design issues. I wouldn't presume to argue with Dunlavy and Thiel and I've heard their remarkable results but I've also heard enough to know that a complex question deserves more than simple dogma. The simplest is to keep the xovers beyond the vocal frequency range, where our ears are most sensitive and wherever those lines are drawn, but that's rarely practical and involves other compromises.
Inductors are probably the worst offenders in passive xovers and they get correspondingly bigger for lower frequency, low pass filters.