Car audio has been around almost as long as the automobile itself, and there have been many changes over the years. Modern systems are typically optimized for both cost and space, which often means making sacrifices in sound quality. Some vehicles come with premium sound packages, but even the car audio equipment in those systems can be customized and upgraded.

The topic of car audio may seem complicated at first, but there are only three basic components that every system must contain. The head unit provides an audio signal, the amplifier amplifies it, and the speakers produce the sound. These components are highly dependent on each other, and the overall quality of a car audio system is determined by how they interact with each other.

At the heart of any car audio system is a component commonly referred to as a head unit. Most people refer to this component as a radio or a stereo, both of which are accurate terms that don’t tell the whole story. Most of these components contain radio tuners, and stereos have been around since the 1960s, but the more general purpose of a head unit is to output some type of audio signal.

In the past, head units provided audio signals from 8-tracks, compact cassettes, and even a proprietary turntable. Most head units now include a CD player, but satellite radio, digital music, and even Internet radio are also popular sources of audio.