The voice coil is made of a thin layer of copper wire that is wound around a former, which is usually made of plastic or metal. The former is attached to the speaker cone, and the voice coil is suspended in the gap between the permanent magnet and the pole pieces by a spider, which is a flexible material that allows the voice coil to move freely.
When an electrical signal is applied to the voice coil, it creates a magnetic field that is either aligned with or opposed to the magnetic field of the permanent magnet. This causes the voice coil to move back and forth, which in turn moves the speaker cone and produces sound. The strength of the magnetic field created by the voice coil is proportional to the amount of current flowing through the coil, so the louder the signal, the stronger the magnetic field and the greater the movement of the voice coil and speaker cone.
The interaction between the voice coil and the magnet is what creates the sound waves that we hear when we listen to music or other audio content. The voice coil is a critical component of a speaker, and its design and construction are essential for producing high-quality sound.