Mid-range drivers are usually cone types or, less commonly, dome types, or compression horn drivers. The radiating diaphragm of a cone mid-range unit is a truncated cone, with a voice coil attached at the neck, along with the spider portion of the suspension, and with the cone surround at the wide end. Cone mid-range drivers typically resemble small woofers. The most common material used for mid-range cones is paper, occasionally impregnated and/or surface-treated with polymers or resins in order to improve vibrational damping. Other mid-range cone materials include plastics such as polypropylene, Cobex, Bextrene, woven Kevlar, fiberglass, carbon fiber, or light metal alloys based on aluminium, magnesium, titanium, or other alloys. The radiating surface of a dome mid-range is typically a 90-degree section of a sphere, made from cloth, metal, or plastic film, with its suspension and voice coil co-located at the outer edge of the dome. Most professional concert mid-range drivers are compression drivers coupled to horns. A very few mid-ranges are electrostatic drivers, planar magnetic drivers, or ribbon drivers.
A mid-range driver is called upon to handle the most significant part of the audible sound spectrum, the region where the most fundamentals emitted by musical instruments and, most importantly, the human voice, lie. This region contains most sounds which are the most familiar to the human ear, and where discrepancies from faithful reproduction are most easily observed. It is therefore paramount that a mid-range driver of good quality be capable of low-distortion reproduction.
Most television sets and small radios have only a single mid-range driver, or two for stereo sound. Since, in the case of television the most important aspect is the talking, it works out well. Since the ear is most sensitive to the middle frequencies produced by a mid-range the driver and amplifier can both be low power, while still delivering what is perceived to be good sound both in terms of volume and quality.