is the practice of utilizing two audio amplifiers
to power a set of loudspeakers
. Horizontal bi-amping utilizes one amp to power both bass drivers (woofers
) and one amp to power the treble drivers (tweeter
)or the midrange and treble drivers, depending on the speaker system. Vertical bi-amping uses a single amp per speaker, with a dedicated channel for the bass driver and a dedicated channel for the treble or the treble and the midrange. In order to vertically bi-amp it is necessary to have either two outputs per channel from the preamp or alternately the pre-out signal can be split by a 1 into 2 "Y" RCA cord. Vertical bi-amping has the advantage of not having to use a single amp to power both bass sections, which can be very taxing on the amplifier, especially at higher volume or if the bass driver has a particularly low impedance at certain frequencies. The speaker system has to be wired to accommodate either configuation, typically with two sets of binding posts, one set for the bass and one set for the mid-highs. A single amplifier can usually power a woofer and a tweeter only through a crossover
filter, which protects each driver from signals outside its frequency range. However, the crossovers themselves waste power; bi-amping along with active crossover components works around this problem by putting crossover networks before the amplifiers rather than between amplifiers and loudspeakers.
The technique is primarily used in large-scale audio applications such as sound amplification for concerts, in portable powered speakers and by hi-fi enthusiasts.
The term derives from the prefix bi-, meaning 'two', and amp, a contraction of 'amplifier'.