Fourth order active crossover

Splitting of the frequency spectrum to drive loudspeaker units is best carried out at low level by active filters between the preamplifier and power amplifers, rather than at high level by passive filters between the power amplifiers and loudspeaker drive units as is commonly the case. Low level active crossover networks do not waste power like their high level passive counterparts, they lead to lower intermodulation distortion, and they allow the power amplifiers to drive the loudspeakers directly.

The active crossover is built from discrete components and op-amps to give a fourth order state variable filter which ensures that the sum of the low pass and high pass output voltages always equals the input voltage, and that the low pass and high pass outputs are always in phase. There are level controls for the high and low pass outputs as well as a damping control to compensate for driver responses at the crossover frequency; which is set by a small plug-in, single in line, resistor pack. Alternatively the crossover frequency can be made variable by means of a four-gang potentiometer.