The PB16-Ultra is a ported box powered subwoofer with a massive 16-inch Ultra driver featuring an 8-inch edge wound voice coil, a stunningly powerful Sledge amplifier with fully discrete MOSFET output, triple 3.5-inch front-firing high-flow ports and an innovative subwoofer control and DSP smartphone app with custom presets for precision tuning. Running dual subwoofers smooths bass response throughout the listening area, increases headroom, reduces localization and provides other acoustic benefits when compared to a single subwoofer.