What is a low pass filter circuit used for on my car amplifier?

A low pass filter is a type of crossover, on a car amplifier. It is designed to filter out the high sounding frequencies that are played on general stereo speakers and tweeters. A low pass filter is usually used on subwoofers to make them play only bass sounding notes. If you have a subwoofer, make sure you turn on the low pass filter, to enhance the sound quality of the bass. When you adjust the low pass filter, you must make sure the low pass hz frequency on your amplifier matches your car subwoofer enclosure hz tuning.