What is a Parametric Processor?
A parametric processor is a type of sound equalizer used in vehicles, should the car's owner want to have it installed in the stereo system. The processor has four bands that are used for compression, expansion, limiting and EQ. The processor has an ARC feature, which stands for Auto-Release Control. This feature offers the stereo system independent threshold, gain, attack, range, release and bandwidth. Each of the four bands has these features to get the most out of the stereo system. A parametric processor sells for roughly $400 per unit and that price does not include installation, should you have a mechanic do the work.
For more info, see How to Use a Car Audio Equalizer