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date: 24 February 2020


  • Alex U. Case


A transducer that converts a signal from the electrical domain into the acoustical, transforming a pattern of changing electrical voltages into a similar pattern of changing air pressures.

Whenever electricity flows, it is accompanied by a magnetic field. Play an audio signal through a wire, and a changing magnetic field forms around it, a magnetic analogy for the electrical variations within. Let that wire’s changing magnetism interact with a fixed magnetic field and it will be pushed and pulled back and forth, a mechanical realization of the electrical signal. When that conductor has a flat ribbon shape, it can energize the air directly and is the basis for a ribbon loudspeaker. Make the conductor a coil of wire and attach it to a piston light enough to vibrate quickly, yet rigid enough to move the air around it, and a moving coil loudspeaker is born.

The loudspeaker driver is often enclosed in a box, with the practical benefit of protecting the components and the acoustical effect of influencing its spectral resonance. Multiple loudspeakers, each optimized for performance in a specific frequency range, may be assembled into a single loudspeaker system whose total output is the sum of the behaviors of the individual speakers—woofers for low frequencies, tweeters for high frequencies, and midrange drivers in between. Subwoofers are systems designed specifically for the lowest frequencies. The electronic crossover circuitry spectrally divides the signal among the specific drivers in a multi-way loudspeaker system. Horns may be fitted on a driver for more efficient and more directional sound radiation. Very small loudspeakers placed over the ear or in the ear canal make-up headphones and ear buds. The loudspeaker is an essential element of some of the most important musical instruments in contemporary popular music styles: DJ mixers, synthesizers, and electric guitars. In addition to material science and manufacturing innovations, loudspeaker development relies increasingly on digital signal processing for detailed measurements, high quality filtering, and room correction....

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