- The loud speaker contains a cylindrical coil which is free to move in a radial magnetic field set up by a strong cylindrical permanent magnet.
- The magnet has a central South Pole and a surrounding North Pole. The field lines are therefore radial and at right angles to the turns of the-coil.
- When varying the current flows through the coil, a force of varying magnitudes will act on the coil. This will cause the coil to move to and fro according to the magnitude of the force.
- The paper cone then vibrates to produce sound waves.