The Sub-Rock is used for additional power handling of bass frequencies when higher sound pressure levels are needed for improved performance. The Stereo Sub-Rock has dual 10" woofers rated at 250 watts power handling, dual separate inputs feeding each woofer with a separate 180 Hz low-pass filter. Sensitivity 93 db spl 1 watt / 1 meter freq. Response 35 hz - 180 hz.