A system's speaker is the component that takes the electronic signal stored on things like compact discs, tapes and DVDs and turns it back into actual sound that we can hear. Speakers are amazing pieces of technology that have had a profound impact on our culture. But they are remarkably simple devices.

The basic principles that speakers rely on are the rules of magnetism. The basic rule of magnetism is that like charges repel, while opposite charges attract. And when the current flows through a conductor, a magnetic field is produced around the conductor.

What are Speakers made up of?

A normal speaker has various different parts which help to produce sound. The most important parts of a speaker are voice coil, magnet, top plate, back plate, pole piece, spider, surround, flex wire, wire terminals, and dust cap.

The voice coil is a winding of copper that is wrapped around a circular drum called a voice coil former. The wire is insulated with a very narrow layer of varnish or plastic so that the winding is still one long conductor rather than just a conductive blob of copper. The ends of the voice coil wire are connected to the terminals on the speaker basket through what is known as tinsel leads. These are very flexible pieces of braided wire that allow electricity to pass. The voice coil is suspended at the top of a large stationary magnet, centered on a plate of steel called a top plate.

The magnetic field created by the magnet is focused on the voice by this metal plate, making it much more intense. As the electrical signals are sent to the voice coil, it sets up a magnetic field around itself as the current flows through the wire. The magnetic field created by this current flow interacts with the magnetic field of the stationary magnet and either draws the speaker down towards the magnet, or pushes it away.

Frequency response is usually the most reliable indicator of a speaker's sound quality. It is also the easiest to manipulate given that it depends on microphone placement, room placement, and how the graph of the response is scaled and smoothed.

To dedicate each driver to a particular frequency range, the speaker system first needs to break the audio signal into different pieces - low frequency, high frequency and sometimes mid range frequencies. This is called the crossover frequency of the speaker. The most common type of crossover is passive, meaning it does not need an external power source because it is activated by the audio signal passing through it. This sort of crossover uses indicators, capacitors and sometimes other circuitry components.

Capacitors and inductors only become good conductors under certain conditions. A crossover capacitor will conduct the current very well when the frequency exceeds a certain level, but will conduct poorly when the frequency is below that level. A crossover inductor acts in the reverse manner. It is only a good conductor when the frequency is below a certain level.