Horn Loudspeaker

A horn loudspeaker is a loudspeaker or loudspeaker element which uses a horn to increase the overall efficiency of the driving element, typically a diaphragm driven by an electromagnet. The horn itself is a passive component and does not amplify the sound from the driving element as such, but rather improves the coupling efficiency between the speaker driver and the air. The horn can be thought of as an "acoustic transformer" that provides impedance matching between the relatively dense diaphragm material and the air of low density. The result is greater acoustic output from a given driver.

The narrow part of the horn next to the speaker driver is called the "throat" and the large part farthest away from the speaker driver is called the "mouth".

Horns have been used to extend the low frequency limit of a speaker driver—when mated to a horn, a speaker driver is able to reproduce lower tones more strongly. The flare rate and the mouth size determine the low frequency limit. The throat size is more of a design choice. Horns have been known to extend the frequency range of a driver beyond five octaves.

Horns have been used to modify the directional characteristics of the produced sound waves. Horizontal coverage angle is the primary determinant of horn width, and vertical coverage angle determines horn height. On- and off-axis performance will differ depending on the shape of the horn. Compromises in performance such as distortions of the wavefront must be balanced against the design goal.