Highs are reproduced by the tweeter, a small driver separate in many systems, but mounted in front of woofer cones in multidriver 2 and 3 way car speakers. Tweeters provide the sizzle and sibilance that give a more lifelike sense of presence to the experience of music. They come in three common types: Cones, Domes, and horns. Tweeters usually do not require very much power to create relatively loud sound. High frequency wavelengths are quite small and only a few watts can generate piercing levels of sound. Compare the tweeter whose radiating surface seems almost rigid, to a typical woofer where the cone may move up to 2 inches.
Cone tweeters are efficient and the most economical. They have a limited dispersion pattern.
Dome tweeters - the type found in most home speakers - have a more linear response and are more accurate. They also have a much wider dispersion pattern than any other type. Some domes are made of metals like neodymium or titanium that yield extended high frequency response. Others are made of Mylar, or a fine cloth like silk for a less extended but somewhat more linear, smoother sound. Some are made from a combination of materials.
Horn Tweeters are powered either by a dynamic (magnet & coil) diaphragm, or by a Piezo driver. They are the most powerful high frequency emitter but more directional, and may lack the extended range of the domes.
A typical car system might consist of a woofer in a box in the rear, midranges at the side and tweeters mounted on or in the dash panel. Here are some more detailed descriptions of the various types and aspects of tweeters.
This term describes the sound-producing element in a tweeter or horn and is the surface that produces the sound you actually hear. The motor that drives it can be any of several technologies including Piezo, conventional dynamic, or ribbon types. See below for a description of each type. Diaphragms do not produce bass and low midrange frequencies well, so they are not usually found in those applications.
The extent to which a sound emitter yields acoustic radiation over a given area, dispersion is a particular concern in tweeters whose portion of the audio spectrum has a much more directional character than woofers. Many horn tweeters, while very energetic, have a more limited area of dispersion within which their effect can be fully perceived. Generally, dome tweeters can be heard over a much wider area, all other factors being equal.
Tweeters are of several different types; cones, horns and domes being the most popular. Dome types are heavily favored in many standard applications. They are efficient, and have low Distortion and wide dispersion. There is a choice between hard and soft dome materials, but all have relatively low mass and high power handling capabilities.
Hard Dome Tweeter
A characteristic of some Dome tweeters in which the dome is made of some light, hard metal such as neodymium, and titanium as well as some of the more rigid plastic compounds. The differences in reproduction between hard ad soft dome tweeters are present, but very subtle. The essential difference is in the higher frequencies that are often reproduced by hard domes, up to 25kHz or more. Since many people tend to have acoustic sensitivity that is sharply reduced or rolls off at 12 to 15 kHz, this may not be an advantage.
Silk Dome Tweeter
Dome tweeters in which the dome is composed of a treated soft silk like material. This is a design that is much less susceptible to mechanical deformation, and yet yields a fairly smooth response over the extent of its range.
A tweeter whose motor is simply a crystal of Piezo material through which the signal current flows. The crystal lattice responds to this by bending in proportion to the Amplitude and frequency of the incoming signal. Piezo tweeters are very efficient drivers and are relatively inexpensive. They come in a large variety of designs and radiators. As a high impedance device, no crossover is needed in most cases.
A driver consisting of a relatively small emitter at the apex of a curvilinear or exponential horn. This is an effective system for radiating high frequencies in a variety of situations. The size and shape of the horn will usually dictate the pattern and use of the driver. Long horns with narrow apertures, tend to have the narrowest radiation pattern, and are very useful in large listening rooms, especially where highly directional effects, such as surround sound requires, are desired. Shallower versions, with wider radiation patterns, have more general applications, especially in car stereo applications where a wider field of coverage is desired, along with a robust driver that can withstand severe environments. In such situations, a Piezo driven emitter (driver) is highly desirable for its ability to handle high-energy inputs on a variable basis.
Bullet Horn Tweeter
A type of Dome tweeter in which the radiator has a large passive, bullet-shaped device above its center that extends the nominal dispersion angle of the sound so that it covers a greater area with a relatively small driver. The illustration in the center of this page is an example.
A driver constructed to reproduce the highest possible frequencies from roughly 10 kHz to well beyond the usual threshold of audibility, 25 kHz and up. While most standard Tweeters can do an excellent job right up to 16 or 20 kHz, these units deliver the most extreme parts of the upper range for those fortunate (or not) few, who can actually hear them.