Voice coil

A voice coil, an electrical coil is used as the drive system of the transducer in acoustic transducers. Application include electro-dynamic speaker or woofer. For dynamic microphones, is in identical working principle, the alternative term moving coil usual.

Construction

The voice coil consists of a thin wire which is wound on the so-called voice coil bobbin. This coil is immersed in the air gap of the permanent magnet, in which a strong magnetic field is. The bobbin is connected with the diaphragm of the speaker unit. The building up of current flow through the alternating magnetic field is moved, the voice coil to the diaphragm to the front and to the rear and thus makes it possible to implement the voltage swings in the air vibrations.

Previously, electromagnets have been used in the construction of the magnetic gap, since it was not capable of producing sufficiently strong permanent magnets instead of permanent magnets. An electromagnet has the advantage that the magnetic field can be changed arbitrarily.

Due to electromagnetic induction, a voltage is induced in the voice coil at a movement of the diaphragm. This fact is utilized in dynamic microphones such as the moving coil microphone advantage. Conventional speakers are suitable only conditionally, as a damping of the diaphragm movement occurs as a dynamic microphone on the principle of eddy current brake. Due to this fact, the electromagnetic damping of the loudspeaker increases with increasing strength of the magnetic field. This requires a low Q-factor, which is also known as " Q ".

There are also self-supporting types of the voice coil, wherein the coil wire has a rectangular cross -section and fully bonded to each other within the windings. Such designs are in high quality speaker chassis used where the moving mass can be reduced by saving the coil support. This benefits of better transient response of the speaker.

Response

The transmitted frequency range depending on the type of infrasound until well into the ultrasonic range. To top it is limited by the mass of the plunger. So can follow large bass speakers only to the lower kilohertz range the frequency of the applied current, for example, the heavy coils. Higher frequencies are not transmitted due to its inertia. Therefore, dividing the frequency spectrum of high quality sound transmission investments across several different speaker type on ( multi-way speakers or separate speakers, subwoofer ).