Speakers and Crossovers

Basically, a speaker is a coil of wire attached to a flexibly mounted cone. The coil, which can move freely, is surrounded by a fixed magnet.  The amplifier (whether a separate power amp or the one integral in the set) produces a variable alternating current which passes into the coil,  generating a varying magnetic field.  This interacts with the magnetism produced by the fixed magnet, and causes the speaker to move in and out depending on the direction of the current.  This in and out movement actually causes the air to move.  The lower the frequency (or note), the more air there is to be moved. As such, speakers designed to reproduce very low, bass notes (Subs) have to be much larger than those designed to handle only the higher frequencies (tweeters) The sound waves are produced to resemble the originals produced by the Tuner (Head Unit).  Because the direction in which the cone moves is dependent on the current, the wires must be connected the same way round on all speakers in the system.  If not, the sound will not be very nice.  This is called 'phasing'.  So make sure all your  +  - terminals are connected  correctly.  To check, take the speaker covers off and watch which way the speakers move, or use a tester.

It is vital to obtain the correct specification speaker to match the rest of your audio system.  One of the most important aspects is power rating, which as you know is measured in Watts (W).  A speaker, like an amplifier will usually have two power ratings on its official specification.  For example, on a speaker marked 10W/30W, the lower figure will be RATED POWER and is the maximum continuous power that the speaker can handle. (This can also be shown in RMS.)  The higher figure is the MUSIC (or MAX) power that the speaker can handle for short periods of time.  The closer together the two power outputs are, the better the speaker.  100W/20W is not as good as a 100W/60W.  Some companies try to fool you this way. "500W Speakers £55".  But when you actually take a look at the small print, the speakers turn out to be 250W etc.  Be careful, know your stuff, know want you want and how much to pay.

What is a Crossover ?
Well, it is a used to split frequencies (either high or low) and determines which frequency goes to which speaker.  Some units are described as 'active' or 'passive'.
A good crossover will offer a way to vary the points at which the frequencies are switched.  Most modern day amps have these built in, but can be quite basic.

What is a Passive Crossover ?
A 'passive' crossover divides the frequencies after amplification.
Passive crossovers use passive components (hence name), such as resistors and capacitors.

What is a Active Crossover ?
An 'active' crossover divides the frequencies before amplification.
Active crossovers use active components such as transistors and integrated circuits.  Because they sort out the frequency separation before amplification, you will
need an amplifier for each frequency separation.

Which is better ?
An 'active' crossover is better, but more expensive.

Not sure if I need a Crossover ?
The sub-bass frequencies have to be separated from all other frequencies.  This means that somewhere down the line, a crossover unit is required.  Once again, there is no, one simple answer.  It all depends on your requirements and those of your system.