Ideally the crossover is designed to defeat this dip, when the two levels add together and compensate for the 3 dB loss. Since a 3 dB change is equivalent to a doubled power increase, when the two levels overlap and add together, the dip in the frequency response will be eliminated. Passive crossovers are normally enclosed in loudspeaker cabinets. The job of the active crossover is to filter specific bandwidths and send them to a number of amplifiers. The active crossover employs the same basic principle as the passive crossover in regards to band pass filters but also includes a built-in line amplifier to compensate for the loss in filter networks.
Some systems combine active and passive crossovers as well.
The low frequencies would be filtered and directed to the woofer. The mids and highs would be filtered by the active crossover and directed to the passive crossover. There the appropriate bands would be sent to the drivers designed to work with the specific frequency range they were given. Low frequencies use up most of the amplifier power, leaving none for the high frequencies. When an active crossover is used, the high frequencies are driven by a separate amplifier, therefore eliminating distortion and increasing the headroom of the system.