Speakers: Parts is Parts
Tweeter History, Cones, and Domes. The Evolution of Tweeter Design
Tweeters are a class of transducers designed to reproduce the upper range of audio frequencies. Most tweeters are electrodynamic drivers, using the usual voice coil suspended within a fixed magnetic field driving some sort of diaphragm. More specifically, these designs operate by applying current from an amplifier circuit’s output to the voice coil.
The voice coil produces a varying magnetic field, which works against a magnet’s fixed magnetic field around which the cylindrical voice coil is suspended, forcing the voice coil — and the diaphragm attached to it — to move. Opposites attract, likes repel, and these forces get the coil to move off its center position. This mechanical movement is exactly analogous (hopefully!) to the electronic signal’s waveform supplied from the amplifier’s output to the voice coil. Since the coil is attached to a diaphragm, the voice coil’s vibratory motion transmits to the diaphragm. The diaphragm vibrates the air creating air pressure or audio waves that we hear as sounds.
Today, most tweeters are dome, balanced drive, or cone. This article by Mike Klasco and Steve Tatarunis, provides an introduction to high frequency drivers, revisiting some key historical designs, and examines these and some of the more esoteric alternatives.