OEM SYSTEMS COMPANY MODEL 500 500-Watt Subwoofer Amplifier Model 500: Subwoofer Amplifier,Frequency Response:	20-300Hz Four independent controls offer flexibility to integrate nearly all subwoofers with the main speakers and the listening environment. The MODEL 500 incorporates a unique subsonic filter adjustable from 20  35Hz that limits/extends power output to the lowest frequency the subwoofer driver is capable of reproducing. The MODEL 500 incorporates stereo Line-Level inputs and outputs that permit the amplifier to be connected between a preamplifier and amplifier without the need for Y-connectors A double-insulated, isolated-ground electrical supply prevents electrical ground loops and reduces the noise floor of the entire audio system.