History of Horn loudspeaker

18.02.2021 – Ladislav Machyna

The principle of sound amplification by horns has been used by people in pre-historical times. Already the first civilizations knew how to use the physical properties of a hollow animal horn to amplify sound. Like everything, we have learned this principle from nature, and the expanding baffle is used in many musical instruments. The physics and mathematics of horn operation were developed for many years, reaching considerable sophistication before WWII. The earliest appearance of the horn in connection to sound in The Times was published in 1786. In 1877, the inventor Thomas Alva Edison used the horn baffle principle when constructing phonograph, where the record moved a heavy metal needle that excited vibrations in a small metal diaphragm that acted as the driver for a horn.

The horn improves the loading and thus gets a better “coupling” of energy from the diaphragm into the air, and the pressure variations therefore get smaller as the volume expands and the sound travels up the horn. This kind of mechanical impedance matching was absolutely necessary in the days of pre-electrical sound reproduction in order to achieve a usable sound level.

Horn loudspeakers are used in many audio applications. The drivers in horn loudspeakers can be very small, even for bass frequencies where conventional loudspeakers would need to be very large for equivalent performance. Horn loudspeakers can be designed to reproduce a wide range of frequencies using a single, small driver; to some extent these can be designed without requiring a multiple drivers and crossover. Consumer audio employs horn loudspeakers for controlled directivity (to limit audio reflections from room surfaces such as walls, floor, and ceiling) and for greater speaker sensitivity. Horn loudspeakers can provide very high efficiencies, making them a good match for very low powered amplifiers, such as single-ended triode amps or other tube amplifiers.

After WWII, some early hi-fi fans went so far as to build low frequency horns whose mouths took up much of a wall of the listening room. The throats were sometimes outside on the lawn, or in the basement. With the coming of stereo in the 1960s, this approach was rarely seen. Many loudspeaker buyers and do-it yourself loudspeaker fans sought smaller designs for aesthetic reasons. Some audiophiles use horn loudspeakers for audio reproduction, while others eschew horn systems for their harmonic resonances, finding in them an unpleasant form of distortion. Since there are a variety of horn designs (of differing length, material, and taper], as well as different drivers, it is, to some extent, impossible to give such blanket characterizations to horn loudspeakers. Audiophiles using low power amplifiers, sometimes in the 5 to 25 watt range, may find the high efficiency of horn loudspeakers an especially attractive feature.

Source: Wikipedia