How do speakers work?
Some of the details (especially of construction) can vary from speaker to speaker, but there are three critical pieces to the sound creation process and these are: the speaker cone or diaphragm, the coil and a powerful magnet. The construction of a speaker using these three simple parts is shown in the figure below.
Looking at each part and what it does will help us understand how a speaker works.
A powerful magnet is a static part of the speaker’s construction. It remains in place and at all times produces a strong magnetic field around it.
Coil or Voice Coil
The two ends of the coil are attached to the audio player (which could be a hi-fi system, a car audio system or the connection to the audio port of the computer). This coil functions like an electromagnet. As an electric current passes through the coil, this causes the coil to move in the magnetic field of the permanent magnet sitting around it.
Speaker Cone or Diaphragm
The cone is made of a thin material and is attached to the coil. As the coil moves back and forth, so does the cone. This vibrating movement of the cone is what produces sound waves, as the air in front of the cone is moved. The frequency of this cone movement determines the frequency of the sound produced.
This basic construction is called a driver. There are of course other pieces such as the frame in which the speaker is housed, a cloth spider which holds the cone in place, etc. but think of these as playing a supporting role in the production of sound. However, one critical piece bears mentioning.
This is an electronic circuit that channels different audio frequency ranges to different speaker/driver types.