An active crossover placed before power amplifiers increases headroom, damping, and reduces distortion versus passive crossovers

A passive crossover network is inserted between the power amplifier output and the loudspeaker drivers. It handles full amplifier power and introduces insertion loss, degrades damping factor, and can introduce distortion from component non-linearities. An active crossover (electronic crossover) divides the audio signal at line level before the power amplifiers, then uses separate amplifier channels for each frequency band (bi- or triamplification). Advantages: each amplifier operates within its designed power range with more headroom; insertion loss from passive components is eliminated; damping factor is maintained (the amplifier output directly controls the driver); distortion from passive components is avoided; each amplifier’s clipping affects only its assigned frequency range (harmonic energy from a clipping woofer amplifier is reproduced mainly by the woofer, not the tweeter).

Examples

A biamplified system using an active crossover at 800 Hz routes 80% of program energy (bass) to a high-power low-frequency amplifier and 20% (HF) to a lower-power high-frequency amplifier. If the bass amplifier clips slightly on a kick drum peak, the clipping harmonics go only to the woofer, which cannot reproduce them efficiently.

Assessment

List three specific disadvantages of a passive high-level crossover that an active crossover eliminates. For each, explain the mechanism.