To adequately reproduce a wide range of frequencies, most loudspeaker systems require more than one driver, particularly for high sound pressure level or high accuracy applications. Individual drivers are used to cover different frequency ranges. The drivers are named subwoofers (very low frequencies), woofers (low frequencies), mid-range speakers (middle frequencies), tweeters (high frequencies) and sometimes supertweeters which are drivers optimized for higher frequencies than a normal tweeter.
A few companies, including Victor Talking Machine Company and Pathe, produced record players using compressed-air loudspeakers. However, these designs were significantly limited by their poor sound quality and their inability to reproduce sound at low volume. Variants of the system were used for public address applications, and more recently other variations have been used to test space equipment resistance to the very loud sound and vibration levels that launching rockets produce.
