Head Units Generate Signals
Perhaps one of the most critical--and certainly the most visible--components of a car audio system is the electronic module that receives radio waves, reads audio media, accepts input from outside music devices, and generates sound signals based on the information contained in these sources. Known as a "head unit," this device typically resides in the dash or console of a vehicle and functions as the primary source of audio for the car system. Whether the unit receives radio waves by way of the antenna and deciphers them, reads digital input from a compact disc or analog input from a cassette tape, or receives direct input from an external device like an iPod, the primary responsibility of the head unit is to convert this input into electrical signals that can be sent out over physically attached stereo wiring. In most applications, the head unit is also responsible for accepting input from the user, usually the driver of the car, and using that input to select the input type, made adjustments to the sound levels being sent to the speakers, or display information on the current audio track.
Speaker Wires Carry Signals
When the head unit sends electrical signals out to the speakers, it is critical that the wires entrusted with those signals have continuity all the way to their destination. In mobile applications like cars, speaker wire is typically very high quality to ensure that the constant vibrations and extreme temperatures do not impede the performance of the wire and degrade its ability to reliably carry the electrical signals. For this reason, car audio wires are usually made of copper with heavy insulation; this insulation also helps protect the signal quality from interference originating from other electrical devices in the car. The terminations of the wires, the small portion that connects to a device on either end of the wire length, may also be plated in gold for enhanced reliability (although gold is somewhat less conductive than copper, it is far more resistant to corrosion). Because the speaker wires are usually very high quality and are run behind door panels, under carpeting, and through conduits out of sight or access to passengers, most car audio wiring will last the entire lifetime of the vehicle.
Speakers Recreate Sound
Although the head unit may be the most visible portion of a car audio system, the vehicle's speakers are by far the most audible. When the electrical signals generated by the head unit arrive at the speakers, powerful electromagnets at the base of the speaker convert the signals into small physical movements. These precise movements are carried outward into the membrane of the speaker, and the membrane motion causes vibrations in the air that are received by the human ear as sound. A typical car audio system may use six speakers (two small "tweeters" to reproduce the highest frequency sounds, two midrange speakers for middle-spectrum sound, and two woofers for lower tones), though high-end vehicles may employ twelve or more speakers for truly accurate reproduction of the entire audible spectrum. Some high end audio systems also make use of powerful amplifiers that boost the electrical signals and magnify the speaker vibrations for a louder sound effect, and large amplifiers may be linked to very large "sub-woofer" speakers to complete the audio experience.
Tags: head unit, electrical signals, input from, audio system, high quality