Polk Audio Monitor Series PSW12 12-Inch Powered Subwoofer (Single, Black) A single 12-inch subwoofer with built-in high-current amplifier for big bass Equipped with one 12-inch polymer-composite dynamic-balance cone driver Features laser-based Klippel measurement technology for improved linearity and deep, precise sound Frequency Response: 26Hz - 200Hz Non-resonant all-MDF enclosure construction with 0.75-inch-thick baffles and internal bracing