The JL Audio CL-SSI signal summing interface lets you use the CL441dsp CleanSweep when you have a factory-installed "premium" sound system that doesn't send full-range signals to all of its speakers.

The CL-SSI combines the bass, midrange, and high-frequency outputs from your premium factory system, and presents a full-range stereo signal to the CleanSweep. The CleanSweep then removes the factory-set equalization from the signal before it travels to your aftermarket amplifiers, speakers, and subwoofers, so you get the best possible sound quality.