Coaxial Driver: A speaker composed of two individual voice coiles and cones; used for reproduction of sounds in two segments of the sound spectrum. Usually used in automotive speakers.

Compliance: The relative stiffness of a speaker suspension, specified as Vas.

Cone: The cone-shaped diaphragm of a speaker attached to the voice coil, which produces pusles of air that the ear detects as sound. Some subs are now made with flat pistons instead of a cone shape.

Coulomb: An amount of electrical charge, which contains 6.24 x 10^18 of electrons.

Crossover Frequency: The frequency at which a driver is crossed over at, usually when response is down -3dB.

Current (I): The flow of electrical charge measured in amperes. D: Effective diameter of driver.

Daisy Chain: The wiring of multiple amplifiers together using the line out wiring options on the amps.

Damping: The reduction of movement of a speaker cone, due to either the electromechanical characteristics of the speaker driver and suspension, the effects of frictional losses inside a speaker enclosure, and/or by electrical means. Damping Material: Any material added to the interior of a speaker enclosure to absorb sound and reduce out-of-phase reflection to the driver diaphragm (cone). Usually acoustic fiberglass, Polyester batting, or poly-fill is used in speaker enclosures.

DC (Direct Current): A flow of electrons, which travels in one direction only.

Decibel (dB): (1) A logarithmic scale used to denote a change in the relative strengh of an electric signal or acoustic wave. It is a standard unit for expressing the ratio between power and power level. An increase of +3 dB is a doubling of electrical (or signal) power; an increase of +10 dB is a doubling of perceived loudness. The decibel is not an absolute measurement, but indicates the relationship or ratio between two signal levels. (2) SPL (sound pressure level) can be measured in dB. 0 dB represents the threshold of normal human hearing, 130 dB represents the threshold for pain.

Diaphragm: The part of a dynamic loudspeaker attached to the voice coil that moves and produces the sound. It usually has the shape of cone or dome.

Diffusion: The scattering of sound. Diffusion reduces the sense of direction of sound source, a useful quality in surround speakers.

Dispersion: The spreading of sound waves as it leaves a speaker.

Displacement: The measurment of cubic volume that an item (such as a speaker or port) takes away from the internal volume of an enclosure, when designing an enclosure this figure must be added to the enclosure volume.

Distortion: Any undesirable change or error in the reproduction of sound that alters the original audio signal or recording.

Dome Tweeter: A high freuency speaker with a dome-shaped diaphragm, usually small in size.