For those of you who dont really know what the different components in car audio systems are or do, i'll try to explain the most common components you will come
across.

COMMON COMPONENTS IN CAR AUDIO!!

• The Head Unit :-  The head unit, or front end of a stereo system is the device used to control your music, it usually has a tape player and a radio wave tuning system, as well as different controls over sound like a bass increase or decrease control, also a treble increase and decrease control, most will come with a channel balance where you can make some channels stronger than other. (e.g make the right speakers stronger sounding than the left.) But basically the front end unit or head-unit is the device used to control what you listen to, weather it be C.D, Radio or Tape. The music signal you hear usually originates from this device.
  
• Amplifiers:-  Amplifiers or more commonly called Amps, take the music siginal supplied from the head unit and amplify it. (e.g make it more powerful). Amplifying the signal is needed to increase the power supplied to the speakers connected to the amp, the more power they get fed, the louder they sound. Some speakers need a amp to be heard like a sub woofer, without an amp, you might as well not have the sub connected to the system. Amps also come with a few controls like cross-overs, filters, bass boost, treble boost and adjustable cut off frequency controls. Amps come with different amounts of channels from 2 to 8, and mabye even more in some. One(1) speaker usually uses one channel, so if you have 4 speakers in your system you might go for a 4 channel amp(note:-i said might go for, its not always the best choice though depending what you want).
  
• Speakers:- Speakers are noise making beauties, the basic concept of a speaker is that it moves air, which is what your ears can feel. There are many different types of speakers designed to produce different sounds.

  1.Subwoofers are used to produce deep bass sound, not just the hearing type, but
  also the feeling type. They really add punch and body to your music and also
  they are good for overpowering road noise.
  2.Woofers are the next up in the frequency scale, they are good for adding power
  to your music without giving off too much bass drown out the other speakers, 
  usually used with tweeters(see below) and a crossovers(the trio are called splits), they
  are needed for every system.
  3.Three-way speakers are the most common type of speaker you will find in a factory
  system, they give out pretty much all of the common frequencies you will listen too.
  They usually dont take too well to bass at high volume, and are really just made to
  compact a system "e.g so you dont have to go out and get a couple of each type of 
  speaker to get an ok sounding system".
  4.Tweeters give out really high freq's, usually not very big in size, they pair up 
  with woofers and crossovers(which splits the signal into two frequencies)