The SSP118 is a high-powered self-amplified single 18-inch subwoofer designed to give you the low frequency output of an average double 18” in a single 18” box. The SSP118 features a single 18-inch subwoofer enclosure with a high-powered 2400 Watt Class-D amplifier. New features on the updated SSP118-MKII Sub, available now. We’ve updated the SSP118 with upgrades for both form and function. New port design. By removing the grill from over the ports, we’ve improved the sound by reducing possible turbulence. This update also increases cooling capabilities by greater air flow through the ports.