Car audio crossovers are probably one of the least understood audio components out there. Because they aren’t absolutely necessary, it’s pretty easy to ignore the topic altogether when building or upgrading a car audio system. Head units, amplifiers, and speakers get all the good press, but that doesn’t mean crossovers aren’t important.

To understand what a crossover is and whether a car stereo actually needs one or more, it's important to first understand some basic principles behind the use of crossovers for car stereos.

The basic idea is that music is made up of audio frequencies that cover the entire spectrum of human hearing, but some speakers are better at producing specific frequencies than others. Tweeters are designed to reproduce high frequencies, woofers are designed to reproduce low frequencies, and so on.

With that in mind, car audio novices are often surprised to learn that every car audio system in existence requires crossovers of some kind. For example, very basic systems that use coaxial speakers actually have small crossovers built into the speakers. Other systems, particularly those that use component speakers, typically use external crossovers that only send the appropriate frequencies to the appropriate speakers.