Just one speaker can reproduce an entire orchestra of sounds. How is this possible? The design is deceptively simple, with incredibly complex potential.
image: Animagraffs
The most common type of driver, commonly called a dynamic loudspeaker, uses a lightweight diaphragm, or cone, connected to a rigid basket, or frame, via a flexible suspension, commonly called a spider, that constrains a voice coil to move axially through a cylindrical magnetic gap.
When an electrical signal is applied to the voice coil, a magnetic field is created by the electric current in the voice coil, making it a variable electromagnet. The coil and the driver’s magnetic system interact in a manner similar to a solenoid, generating a mechanical force that moves the coil (and thus, the attached cone).
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Application of alternating current moves the cone back and forth, accelerating and reproducing sound under the control of the applied electrical signal coming from the amplifier. Like a drum skin vibrating back and forth, the moving cone pumps sounds out into the air. This is why loudspeakers are technically called drivers: they “drive” (move) the air to produce sound.
