Voice coil

The wire wound inside a Speaker Driver through which voltage is applied that causes the Cone to push air. Works because of the electromotive force the Coil induces between itself and the permanent magnet.

The computer industry discovered it can also use the voice coil for very fast and precise linear positioning. Changes in voltage will correspond to a change in force or position, and thus (with some feedback control) can be used to control the position of a head in a hard disk.

Typically the control feedback used to calibrate the voice coil is magneticly stored data on the same platter with the regular disk data, which makes low level formatting the drive a bit tricky, and only possible at the factory.

This was brought to you by the Save Our Archaic Technical Terms Society. Thanks to TinCanFury for his excellent speaker nodes.

Electromotive force (emf) isn't the force that drives the speaker. That's just plain two-magnets-repelling-each-other.

EMF is the force that pushes electrons through the wire, generating current. Current through a loop (voice coil) makes a magnetic field that pushes and pulls against a fixed magnet. That fixed magnet is connected to a cone and sound is born :)

glad that's cleared up :)