A voice coil is directly defined as a coil that passes through audio current. It is an important part of the vibration system of a dynamic speaker, and is nothing less than the heart of a speaker. The performance of the voice coil will affect the speaker's sound pressure frequency characteristics, sound pressure level, impedance curve, distortion, transient characteristics, speaker parameters, sound quality, etc. It is especially related to the maximum power and service life of the speaker. Akin to the fatal factor of heart disease, damage to a speaker usually starts from the voice coil.

The role of voice coil

(1) When the current I passes through the voice coil in the speaker’s magnetic gap with the magnetic field strength of B, the voice coil will be subject to an electromotive force F=BLI (L is the length of the voice coil); the force direction is subject to the left-hand rule.

(2) After the force occurs, when the vibration system including the voice coil vibrates at a speed V, an induced voltage BLV is generated inside the voice coil whose direction is subject to the right-hand rule, and is contrary to the original current direction. At this time, the voice coil is both the initiator and the bearer of damping.