A majority of the most critical audio information is found in the midrange frequencies, which makes speaker selection for this band vitally important. The dominant energy of the human voice, whether speaking or singing, is found in this range, as well as that of many musical instruments. Adding a woofer or tweeter to this foundation adds realism!
Many loudspeaker systems utilize a midrange or midbass driver of some type, either in the combined role of woofer-midrange in small 2-way loudspeakers, or as a dedicated "middle-range" driver in 3-way systems and more. Yet another variation is the full-range speaker, which appears singly in super-compact enclosures, transmission lines, rear-loaded horns, or in multiples like line array loudspeaker systems.