what is crossover frequency
The crossover is the circuit in the speaker which controls which frequencies each individual driver (woofer, midrange, tweeter...) plays. The crossover frequency is the frequency at which one driver 'takes over' from another. The crossover is a passive analog circuit consisting of resistors, capacitors and inductors, and are not 'brickwall' filters; around the cross over frequency, both drivers will be emitting sound.