• Car surround sound setups use several different types of speakers and other components.mini car speaker image by robert mobley from Fotolia.com
  
  Car surround sound setups contain a few different core components to get the noise from your favorite media to your ears. Stereos can come with several different speaker types and layouts. However, a car audio system goes much further than the speakers alone. The sound needs to be amplified, sorted out and sent. This is the function of amplifiers and crossovers. Digital technology in head units has advanced in the world of car audio, necessitating a variety of components for that true total audio immersion feeling that will not come with a basic two- or four-speaker setup.
  
  

Head Units

• A head unit is contained within the dashboard and is used for driver control of the audio system. It usually contains a CD player and an auxiliary input for MP3 players such as the iPod. Newer units also often contain hard drives and USB ports for interfacing with external devices. User input can be through a touch screen or by pressing traditional buttons. Hands-free spoken control is quickly becoming another popular way to interface with head units.
  
  

Speaker Types

• Surround sound car audio systems use coaxial speakers, meaning different speakers reproduce different areas of frequency for a complete sound that the ear can hear. Car audio speakers are divided into tweeters, mid-range and subwoofers. Tweeters produce the highest frequencies. Mid-range are divided among high-mid and low-mid and produce the bulk of the sound that you can hear. Subwoofers produce the lowest bass frequencies. All are essential to a quality surround sound system.
  
  

Speaker Placement

• Tweeters are usually located above the dashboard at the top corners, approximately at side mirror level. Some systems have tweeters within the headrests. Surround sound systems have several high-mid and low-mid speakers, placed in the door panels and behind the rear headrests. Subwoofers are located in the trunk. Top quality systems such as those found in luxury cars often have a much higher number of each type of speaker, especially multiple high-mids and low-mids placed all over the car to ensure a complete sound from any seating position.
  
  

Amplifiers

• Inexpensive head units have an amplifier built in, while a true surround sound system uses dedicated stand-alone amplifiers. Often one amplifier will be used for the main speakers with another dedicated amplifier for subwoofers. Amplifiers are rated in wattage and ohms, where watts measure the peak power and ohms measure electrical impedance. An amplifier with higher wattage will produce greater audio volume. Ohms affect how each speaker handles all that power.
  
  

Crossovers

• The crossover splits audio into frequency bands, which are then sent to each type of speaker. Without a crossover, all the audio frequencies would be sent to each speaker. Sending bass frequencies to a tweeter, for example, would cause it to blow immediately and be rendered useless. Crossovers function in tandem with amplifiers to send audio signals from the head unit to each speaker type in turn for a complete surround sound system.