Tweeter

A tweeter or treble speaker is a special type of loudspeaker (usually dome or horn-type) that is designed to produce high audio frequencies, typically from around 2,000 Hz to 20,000 Hz (generally considered to be the upper limit of human hearing). Specialty tweeters can deliver high frequencies up to 100 kHz. The name is derived from the high pitched sounds made by some birds, especially in contrast to the low woofs made by many dogs, after which low-frequency drivers are named (woofers).

Nearly all tweeters are electrodynamic drivers using a voice coil suspended within a fixed magnetic field. These designs operate by applying current from the output of an amplifier circuit to a coil of wire called a voice coil. The voice coil produces a varying magnetic field, which works against the fixed magnetic field of a magnet around which the cylindrical voice coil is suspended, forcing the voice coil and the diaphragm attached to it to move. This mechanical movement resembles the waveform of the electronic signal supplied from the amplifier's output to the voice coil. Since the coil is attached to a diaphragm, the vibratory motion of the voice coil transmits to the diaphragm; the diaphragm in turn vibrates the air, thus creating air motions or audio waves, which is heard as high sounds.

Modern tweeters are typically different from older tweeters, which were usually small versions of woofers. As tweeter technology has advanced, different design applications have become popular. Many soft dome tweeter diaphragms are thermoformed from polyester film, or silk or polyester fabric that has been impregnated with a polymer resin. Hard dome tweeters are usually made of aluminium, aluminium-magnesium alloys, or titanium.

Tweeters are intended to convert an electrical signal into mechanical air movement with nothing added or subtracted, but the process is imperfect, and real-world tweeters involve tradeoffs. Among the challenges in tweeter design and manufacture are: providing adequate damping, to stop the dome's motion rapidly when the signal ends; ensuring suspension linearity, allowing high output at the low end of its frequency range; ensuring freedom from contact with the magnet assembly, keeping the dome centered as it moves; and providing adequate power handling without adding excessive mass.

Some tweeters sit outside the main enclosure in their own semi-independent unit. Examples include "super tweeters and the novel "egg tweeter" by Ohm. The latter plugs in and swivels to adjust the soundfield depending on listener position and user preference. The separation from the baffle is considered to be optimal under the theory that the smallest baffle possible is optimal for tweeters.

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Wikipedia