The truth is that these drivers all have output down to, say, 22Hz, but a single driver can't provide enough usable output to rate the speaker + or- 3dB to 22Hz -perhaps only 28 Hz.
Add more drivers, you have more usable output at low frequencies, and the crossover and cabinet design integrate them into the total frequency spectrum smoothly
Add more drivers, you have more usable output at low frequencies, and the crossover and cabinet design integrate them into the total frequency spectrum smoothly