Horn loudspeakers or funnel loudspeakers have the shape of a funnel with constantly increasing horn cross-section for sound emission. If the funnel opening runs exponentially, the corresponding horn loudspeaker is called an exponential horn. The sound pressure is generated by the horn driver, which consists of the pressure chamber of an electrodynamic oscillating system, and radiated via the horn attachment, which forms the sound channel.
The sound pressure of horn loudspeakers can only exit to the front. Due to the tapering of the pressure chamber toward the outlet horn, the highly compressed air generated by the horn driver has a high flow velocity and high acoustic impedance at the outlet port. The sound pressure level( SPL) increases in a certain listening area and the directivity of the sound to the listener increases. Thanks to the exponential or hyperbolic funnel shape, funnel loudspeakers have a better impedance match to the sound characteristic impedance of air than cone loudspeakers and therefore have a higher efficiency. They operate at high sound pressure and are therefore also called pressure chamber loudspeakers. The sound pressure is relatively high at low power levels. For example, a power of 2 watts can be converted into a sound pressure of 110 dB at a distance of one meter.
Since the directivity of horn loudspeakers changes with higher frequencies, the CD horn, Constant Directory Horn (CD), is a horn loudspeaker that has the same sound pressure at all frequencies.
Funnel loudspeakers are specified according to protection classes and used in PA systems. Because of their direction-sensitive sound emission, they are also found outdoors in train stations, in halls, at airports. The lower cut-off frequency is determined by the cross-section of the funnel opening, the funnel size and the funnel constant. The funnel length is decisive for the sound pressure gain.
Because the frequency range of funnel loudspeakers favors midrange pitches, they are not suitable for high-quality audio, but for announcements and alarms. The exponentially shaped funnel gives the funnel speaker a lobe-shaped dispersion pattern. Their power ratings range from 10 W to 50 W. PA horn speakers exceed these values many times over and can have power values of several hundred watts as tweeters. PA woofers even reach over a thousand watts of rated power handling.