Bi-amping and tri-amping

With ordinary loudspeakers, a single amplifier can power the woofer, mid-range and tweeter through an audio crossover, which filters the signal into high- medium- and low-frequencies (or high- and low-frequencies in 2-way speakers) – a mechanism that protects each driver from signals outside its frequency range.

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.

A single amplifier can usually power a woofer and a tweeter only through a post-amplifier crossover filter, which protects each driver from signals outside its frequency range.

Bi-amping of speakers requires double the channels of amplification and can be accomplished using two ordinary amplifiers in either a vertical or horizontal arrangement.

[2] In large professional sound systems, Bi-amping is pretty much the norm with the greater benefits easily outweighing the costs.