Passive VS Active crossover-What s the difference s

Hi All,
Would you explain the difference between a Passive X-over and an Active X-over? What kind is needed (and IS it?) for Bi-amping? Any recommended models - new or used?
The job of the crossover is to divide the full range signal into ranges that the individual speakers are designed to handle. Using a two way speaker as an example, high frequencies to the tweeters, low frequencies to the woofers.

A passive unit contains only passive components, i.e. resistors, capacitors, inductors, switches, wire, etc. These are located after the power amp, usually inside the speakers. The high pass and low pass sections are sometimes accessed separately via two pairs of input terminals allowing the speaker to be hooked up in a bi-wire configuration. Bi-wire is one power amp with two sets of speaker wires.

An active unit is made with devices that can amplify the signal, i.e. tubes and/or transistors. The signal is divided after the preamp and before the power amp so it requires four channels of amplification that are attached to the individual drivers. two channels for the high frequencies and two more for the low. This requires a speaker that is designed to have it's internal crossover disabled or modifying the speakers. This is bi-amping.

Another option for bi-amping is to use four amplifier channels running full range hooked to the bi-wire terminals and allowing the internal passive crossover to allow only the desired frequencies to reach the drivers.
Another benefit to actively crossing over is that amplifier efficiency is DRASTICALLY increased. Since there are no passive parts to "suck up" and waste power between the amp and speaker, the system can play louder with less work on the amps' part. Sound quality ( when properly set up ) is also much better. In other words, active bi / tri / quad amping IS the way to go if you have the time, patience and know how. Sean
I'll make only one point: you can certainly have a passive dividing network coming BEFORE the power amps. You may need a buffer between it and the preamp, though. It's hard to get right, but not impossible, and the sonic benefits could be considerable.
Sean, I agree with you on your post regarding dynamic drivers bi, tri, and quad amped.....but we need to mention that the introduction of an active X-over into your ultra hi end setup, could well destroy the purity of the electronics you are using. I have tried the original Levinson LNC-2, the now defunct Symmetry (much better) and ARC. The hi pass sections of these were NOT up to the quality of my preferred electronics and hurt the sound everytime.
Electrostatics like the QUAD ESL-63 also are hurt by the disruption of the crossoverless signal purity. I tried everything to relieve the panels and increase dynamics, but everytime the sound was better without. My ultimate solution was to stack the ESL-63 full range, thus yielding maybe 3db more output, and more surface launch area; then overlap the subs with an electronic X-over Without using the hi pass section.
Stacking of dynamic loudspeakers, though, can mess up the accurate time response of a well designed loudspeaker.
We went through this when we stacked Rogers LS3/5A's to make them "bigger". "No, no, no" was the reaction on that issue. "something isn't quite right anymore"...........Frank