Three-way loudspeakers are among the best sounding speakers available in the pro audio world today. The frequency span that the human ear can detect stretches from 20 Hertz to 20,000 Hertz. Reproducing this wide frequency is hard for a loudspeaker that only has two speaker components in it, a woofer, to handle the low frequencies, and a compression driver to produce the high frequencies.
The woofer is there to make the low-end happen. The kick drum, the bass guitar, and a little bit of the human voice is reproduced by the woofer in an average two-way speaker. All the rest of the signal, say 1,500 Hertz and above, is fed to a compression driver that is expected to accurately reproduce the middle and upper frequencies. This is nearly impossible without a huge sacrifice in sound quality. In a two-way loudspeaker, we are simply asking too much from a box that is only capable of doing so much heavy lifting.
In a three-way loudspeaker, we introduce a third driver, one whose job it is to reproduce just the mid-range audio signals. This usually includes most of the human voice, so you get a better reproduction of the human voice from a three-way speaker, than any other pro audio speaker. The added benefit of a three-way speaker is that the high frequencies are less distorted at high volume levels, because the compression driver is not trying to reproduce signals below its optimum operating frequency range.