If you sometimes wonder what your speaker’s membrane is or why it’s moving around, the following should be of interest to you. A loudspeaker is composed of a mobile copper coil, housed in the air gap of a powerful magnet, which moves at the mercy of the electric current sent to it by the amplifier and the constraints of the magnetic field generated in the gap by the magnet. The voice coil carries with it the diaphragm of the loudspeaker which moves and brings the air in vibration to generate sounds. The voice coil is attached to the core of the speaker diaphragm (the visible cone), the latter being held by a double suspension system. The first suspension surrounds the cone. Half-roll type, it is attached to the frame of the speaker is called the salad bowl.
The bass speaker
Its coil is of strong section to accept a large amount of electric current. Implicitly, the voice coil weighs the diaphragm, which is inherently thick to impress the air with high inertia to make it vibrate at the lowest frequencies. Some speakers are even equipped with additional masses, attached to the back of the membrane core cover, to make it resonate at a very low frequency. This is mainly the case of passive speakers.
Commonly referred to as the “motor”, the magnet functions to control the movements of the voice coil in its gap. It is its magnetic field that acts as a guardrail and prevents the coil to make excessive excursions and damage the rest of the mobile equipment (spider, membrane, suspension). Currently, the alloy with the best magnetic properties is neodymium. Its yield is excellent and its magnetism particularly durable.
The voice coil
It is a succession of turns of copper wire, wrapped around a core. The electricity sent by the amplifier causes the coil to move in the magnetic field naturally generated by the magnet. The physical characteristics of the coil largely determine the power handling of the loudspeaker (expressed in W).
It is the metal cylinder integrated in the magnet in which the magnetic field is concentrated. This is the playground in which it is imperative to remain the voice coil, under penalty of causing an unbearable distortion of the sound signal and damage to the speaker.