SMP100 Class D Digital Subwoofer Amplifier is a compact 100W amp designed to power passive subwoofers used in home theaters or whole house audio systems. We call this our 'tiny but mighty' powered sub because it measures less than six inches wide but supplies an in-wall or stand-alone subwoofer the power it needs so you can experience room-shaking low frequency impact (bass) on movie and music soundtracks. The advanced crossover circuit can be set at different frequency ranges (35Hz to 160Hz) and can be adjusted with the front-panel control knob. Other features include front-panel adjustable phase and volume controls to dial in just the right amount of low frequency effects (LFE).