Active vs Passive Crossover

Active crossover allows the user to properly bi-amp or multi-amp. 

Active crossover is before the amplifiers; passive crossover is after the amplifier.

Active crossover goes between the preamp and the amplifiers. 
Each speaker driver is connected directly to its dedicated amplifier. 
The passive crossover between the speaker drivers and amplifier is completely eliminated.

Analog vs Digital Active Crossover
-With analog active crossover, the analog signal from the preamp is filtered with analog filters (resistors and capacitors.)
 Then the signal comes out as analog to enter the amplifiers.
-With digital active crossover, the analog signal from the preamp is converted to digital.
 Then the digital signal is filtered with digital processor.
 Then the filtered digital signal is converted back to analog to go to the amplifiers.
 These two conversion processes destroy the sound.

A fully active multi amps system is the ultimate.
With a dedicated amplifier driving each individual driver, the amplifier can be optimized for that driver 
(for example: high power amplifier for woofer; low power amplifier for tweeter.)
The individual driver receives the full power from its amplifier. 
With a passive crossover, a LOT of the amplifier's power is lost in the passive crossover.
In an active multi amps system, the upper amplifiers do not have to work hard because they are not amplifying the bass signal.
Since bass signal has high distortion, this means low distortion for the upper amplifiers and drivers