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.
When multiple drivers are used in a system, a "filter network", called a crossover, is used to separate the incoming signal into different frequency bands appropriate for each driver. A loudspeaker system with n separate frequency bands is described as "n-way speakers": a 2-way system will have woofer and tweeter speakers; a 3-way system is either a combination of woofer, mid-range and tweeter or subwoofer, woofer and tweeter.
