ALTO's black SXSUB15 15" Passive Subwoofer has a frequency range and crossover designed to deliver smooth, low-end sound production from 45 to 200 Hz. Your kick drum will thud, your bass guitar will rumble, and your beats will inspire you to get your groove on when used with two- and three-way speaker systems. Because of its large low-end response, the passive subwoofer allows you to run your PA at a lesser volume while still getting a big, complete sound.