The Speaker

The loudspeaker consists of a speaker cone, which as the name suggests is cone shaped. This is the paper sheet that moves backwards and forwards to move the air and create sound waves. The cone is attached to the speaker surround by a flexible rim that holds the outer part of the speaker cone but will allow it to move. The centre of the cone is attached to a coil of wire. This coil is usually concealed by covering it with domed cap. It is this coil that causes the cone to move. This coil of wire is sitting in the centre of a magnetic field. If we now pass a current through this coil it will generate a current and thus a magnetic field, as the speaker magnet has more mass and thus more inertia the coil will move inside the magnet. If the current is reversed the coil and thus the speaker cone will move in the opposite direction. Those are the basics; apply a voltage to your speaker which will cause a current to flow in the coil creating a magnetic field that moves the speaker cone.

The loudspeaker cone

This is the main component of a speaker, and it is the cone that is the main determinant of how the speaker will sound. The cone carries the coil and it is this paper that is the mechanical part of the transducer known as a loudspeaker. The cone holds the coil in a precise position so that it can only move backwards and forwards and not from side to side. It is the cone that provides the restoring force needed to return the cone to its centre position under no-signal conditions. The materials for the cone have to be strong and not tear. The material must retain its shape and not stretch, shrink or warp. and it must have low mass or weight.

As the speaker consists of a coil in a magnetic field it means that the speaker will work in reverse. If we move the speaker cone backwards and forwards then we will move the coil in a magnetic field which is equivalent to moving a magnet in a coil. This will generate a voltage. The loudspeaker can be used as a microphone. The science is the same only the purpose and thus the design is different. The speaker has the job of moving a large amount of air from an electric current and the microphone has the job of producing a voltage output from a small amount of air pressure.