The purpose of this circuitry is to split up the full range of frequencies into a number of bands, e.g. with multi-channel speakers. Each driver is then supplied with the range of frequencies for which it was originally designed. This is done by means of filter circuitry. There are a number of different technical methods available: - analogue, passive: using coils, capacitors, resistors - analogue, active: using electronic circuits - digital, active: using electronic circuits. In addition we distinguish between the methods used by their characteristics: - high-pass filter: low frequencies are rolled off - low-pass filter: higher frequencies are rolled off - bandpass filter: both the lower and higher frequencies are rolled off. The frequency response of the loudspeaker can be additionally affected by the way the crossover is designed. The general rule is: use as few components as possible but use as many as you need! It is in any event important to dedicate some thought to the crossover because this unit has a considerable effect on the overall sound quality.