The SWA500 is custom engineered to power Polk Audio's CSW Series of built-in subwoofers to rafter-shaking, distortion-free levels. Class D digital design delivers huge power and runs cool for superb long-term reliability 500 Watts into 4 Ohms at Powers up to two CSW subs of the same model Front panel Low Pass Filter and Level adjustment knobs make `tweaking` a snap. Plug in SPEX circuit cards (supplied) optimize the amplifier to match the specific subwoofer model being used Custom frequency shaping (programmed into SPEX card) for the deepest, most accurate bass ...