A crossover network is used to select which frequency components of a signal are passed to the different speakers available. A crossover network may be:

- an active crossover network, or
- a passive crossover network.

A crossover network would typically select high frequencies to be passed to a tweeter, and low frequencies to be passed to a woofer. An important design goal for the crossover network is to ensure that the equal sound volume can be produced at all operating frequencies.

An active crossover network includes some form of amplification, as well as passive elements. An active crossover system is often located prior to power amplification, and so operates at low power. An active crossover may also incorporate the power amplifier. An active crossover network may be located within the speaker enclosure, or be housed separately.

A passive crossover network is a crossover network that consists of only passive elements, such as resistors, capacitors and inductors. A passive crossover network is commonly used inside a speaker system, since it does not require a power connection.
HTH