Consists of a powerful magnet and a coil of fine wire, the voice coil wrapped around a lightweight cylinder connected to a cone. The voice coil and cone can move back and forth as far as the suspension allows. The suspension however firmly holds the voice coil and cone in a central position otherwiseh the voice coil would rub against the magnet. For clarity the frame, which must be sturdy, is not shown. The free ends of the suspension and the magnet is supported by the frame.

The terminals are usually marked positive (+) and negative (-)o that two or more speakers are phased the same, or move in and out together when fed with the same signal. If a battery is connected to the terminals a current will flow through the coil to give a magnetic field with a south pole at one end of the coil and a north pole at the other. Like poles repel and unlike poles attract.

If as shown in the diagram, the cone will be pulled towards the magnet. When the current is reversed the voice coil north and south poles are reversed. The cone will be pushed away from the magnet as the south pole, now at the bottom of the voice coil will be attracted to the permanent north pole of the magnet and the north pole at the top of the voice coil will be repelled by the north pole of the magnet.

A sound signal has an alternating current waveform, continually changing from positive to negative so the speaker cone will move back and forth in step. The cone pushes the air in front of it and produces a sound wave.

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