The sound system fitted in an automobile can be described by the term car audio. Little different is the stock car audio system which refers to one that was specified by the manufacturer when the car was built. On the other hand, custom car audio installation can involve anything from the upgrade of the radio to a full-blown customization of a car based around its audio equipment like car stereo CD changers.

The audio equipment commonly used is the radio, tape player, CD player, DVD Player. These are generically described as a Head unit. The addition of CD players with MP3, WMA, AAC, and USB, Bluetooth and Wi-Fi support are new developments in head unit technology.

Most modern cars include at least a CD player/ CD recorder, and some have the option for car stereo CD changers, which hold multiple disks either in the head unit itself or in a separate unit usually located in a trunk or console. The main types of CD changers are External Cartridge, Internal Cartridge and Carousel CD changers.

The stereophonic sound, commonly called stereo, is the independent reproduction of the sound using two or more channels audio in way to create a natural impression of the heard sound from several directions, similar to that one in the natural hearing. In popular use, stereo audio of the car means generally the recording of 2 sounds on 2 channels and the reproduction of the sound using the data for more than a loudspeaker simultaneously.

During the time of mono radio, the most common speaker location was in the middle of the dashboard pointing through perforations towards the front windshield. With the advent of stereo system, car audio speakers are located in doors and rear parcel shelves in modern cars. High-end or competition stereo systems like car stereo CD changers have speakers mounted in kick panel enclosures, allowing for larger drivers and better driver placement.

The amplifiers are used to drive the speakers. These provide the necessary music power, which is measured in watts. An amplifier is a very important component of good car audio speakers system. One should always ensure that the total power handling capacity of the speakers connected to the amplifier or head unit is greater than the power of the amplifier or head unit.