The evolution of high performance bass. 
Polk Audio PSW125 Black Subwoofer
Explosive performance for movies and music.
Compression Circuitry limits distortion at earth-shaking volume levels. 
Built-in High Current Amp supplies all the good, clean power you need for big bass. 
LINE and SPEAKER level inputs ensure easy hook-up compatibility 
Signal-sensing Auto ON/OFF Circuitry knows when to turn itself on and off 
Non-resonant MDF construction with internal bracing
Manufacturer's Description
The PSW125 Powered Subwoofer delivers powerful, accurate and musical bass at shockingly low prices. Built for power and value, the PSW125 represents a continuing refinement of the highly regarded PSW Series and a great introduction to visceral home theater bass performance. 

PSW125 Features: 
12-inch Dynamic Balance Composite Woofer Driver creates "tight, musical bass. 
Downward firing port couples to the room for more bass impact. 
More powerful motor structure for a higher BL product,(the measure of the motive force applied to the cone) results in louder, deeper and punchier bass than previous Polk woofers in this price category. 
Klippel Optimized woofer - By using a state-of-the-art Klippel Distortion Analyzer, Polk engineers were able to optimize the woofer`s motor structure, voice coil alignment and suspension for the best possible performance even at extreme listening levels. 
Compression Circuitry limits distortion at earth-shaking volume levels. 
Built-in High Current Amplifier supplies all the good, clean power you need for big bass. The PSW125 features a Class A/B amp. 
LINE and SPEAKER level inputs ensure easy hook-up compatibility with virtually any system, while the PSW125 also has an Unfiltered LFE Input for use with low-pass filtered subwoofer output jacks. 
Amplifier features: Adjustable Low-Pass Crossover, Phase Switch and Subwoofer Volume Control to more easily control your bass output and the sub`s blending characteristics with your front stage speakers. 
Signal-sensing "smart amp Auto ON/OFF Circuitry "knows when to turn itself on and off. 
Non-resonant MDF construction with internal bracing for deep bass impact with superior detail, accuracy and musicality.