D - Effective diameter of driver, in meters.
DAC - Refer to Digital-to-analog converter
Data-2-Data (D2D) - "Data to data" connection of an alarm/remote starter to bypass module.
Damping - The reduction of the magnitude of resonance by the use of some type of material, typically achieved by adding mass to an object. The damping material converts the energy of unwanted resonant vibrations into heat.
Damping Factor - This is a quality which defines how quickly the amplifier can stop a reproduced frequency such as a bass note. The higher the damping factor, the better the amp will control the woofer and help reduce overhang distortion. The damping factor of an amplifier is mostly dependent on the quality for the power supply which feeds the power amp.
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 Polyfill is used in speaker enclosures.
dBr - The expression dBr is used to define signal at RF and AF frequencies. The symbol is an abbreviation for “decibel relative to reference level.” The dBr increment is based on the decibel, a logarithmic measure of relative signal strength.
DC - Refer to Direct Current
DC/DC Converter - A DC-to-DC converter is an electronic circuit or electromechanical device that converts a source of direct current (DC) from one voltage level to another. It is a type of electric power converter. Power levels range from very low (small batteries) to very high (high-voltage power transmissions).
Decade (dec) - One decade is a factor of 10 difference between two numbers (an order of magnitude difference) measured on a logarithmic scale. Along with the octave, it is a logarithmic unit used to describe frequency bands or frequency ratios. It is especially useful when referring to frequencies and when describing frequency response of electronic systems, such as amplifiers and filters.
Decibel (dB) - (1) A logarithmic scale used to denote a change in the relative strength of an electric signal or acoustic wave. It is a standard unit for expressing the ratio between power and power level. Using the logarithmic relationship for power PdB = 10*log[Pout/Pin], a doubling of electrical power only yields an increase of + 3dB. Increasing the power tenfold will yield an increase of +10 dB and is a doubling of a 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 represnts the threashold of normal human hearing, 130 dB represents the threashold for pain, 140 dB causes irreparable hearing damage, and 150 dB can casue instant deafness, anyting greater than about 192 dB can kill you.
Dedicated Fuse - A Fuse designated to supply power ad protection for one particular circuit only.
Destructive Interference - A phenomenon that occurs when speakers are 180 degrees out of phase. For example, what one speaker is trying to produce, the other speaker is fighting to cancel. One speaker’s wave is in the positive phase (pressure), while the other speaker’s wave is in the negative phase (rarefaction).
Detent Controls - A detent is a device used to mechanically resist or arrest the rotation of a wheel, axle, or spindle. Such a device can be anything ranging from a simple metal pin to a machine. The term is also used for the method involved. Detents are for example used to simply arrest rotation in one direction or to intentionally divide a rotation into discrete increments.
Deutsche Industrie Normen - DIN radio. A standard automobile radio body size. A DIN radio (single DIN) measures 2” X 7” and a double DIN measures 4” X 7”. When factory radio/CD players are replaced with aftermarket units, the DIN standard ensures compatibility. However, some new dashboard trims or bezels may be require alteration. DIN also refers to industrial standards that are used in the manufacture of many goods used in Europe, especially German made OEM automotive parts. Also refer to Single DIN and Double DIN.
Dial Up Network (DUN) - This is a profile extension of SPP and connects to a device through Bluetooth to a modem, whether a fixed-line or mobile phone data connection.
Diagnostic Trouble Code (DTC) - A five character code generated by the on board diagnostics system in 1996 and later vehicles indication the nature of a malfunction or problem.
Diaphragm - Also known as the cone, the part of a dynamic loudspeaker attached to the voice coil that moves and produces the sound. It usually has the shape of a dome or a cone.
Dielectric - a medium or substance that transmits electric force without conduction; an insulator.
Difference of Potential - The total numeric value measured between two points of different electrical potential. Difference of potential is commonly called “Voltage”.
DIFM - Refer to Do-It-For-Me
Diffraction - A change in the direction of a wave that is caused by the wave moving past or hitting an obstacle.
Diffusion - The scattering of sound.
Digital Media Files - Music which has been subjected to data compression — allowing users to store many hours of music as computer files. A growing number of in-dash CD receivers have the ability to decode and play recordable CDs (CD-Rs and CD-RWs) loaded with MP3, WMA, AAC, or WAV files. A single disc can hold up to ten hours of music.
Digital Multi-meter (DMM) - A digital multi-meter is a test tool used to measure two or ore electrical values- principally voltage (volts), current (amps) and resistance (ohms).
Digital Receiver - Digital media receivers are in-dash receivers that do not have CD players built in. Instead, they feature multiple inputs for devices like iPods, USB drives, SD cards, and so on.
Digital Sound Processor (DSP) - The process of analyzing and modifying a signal to optimize or improve its efficiency or performance. It involves applying various mathematical and computational algorithms to analog and digital signal to produce a signal that’s of higher quality than the original signal.
Digital Time Delay - A precise time delay of an electronic signal. Specifically an audio effect in which an input signal is digitally stored and played back after a given period of time. Typically utilized to simulate the acoustic properties of a particular type of environment.
Digital to Analog Converter (DAC) - A component or circuit that is used to derive or convert an analog signal from a digital one. This turns on/off pulses into analogue sound. CD players have DACs built in. Separate DACs can upgrade a CD player or other digital player/ recorder, or can be used with dedicated CD transports.
DIN - Refer to Deutsche Industrie Normen
Diode - An electrical component that enables easy electrical current flow in one direction and not the other.
Dipole - A speaker design which generates equal amounts of sound both forward and backward, with the two sounds being out of phase. Dipoles are often used as surround speakers. Similarly known as Bipole.
Direct Current (DC) - Electrical current flowing in only one direction.
Discharge - An electric discharge is the release and transmission of electricity in an appliedelectric field through a medium such as a gas.
Distortion - Refers to the deforming of a waveform at the output of a device as compared with the input, usually due to overload, creating a distorted or “dirty” signal. While electrical or audio distortion is typically unwanted and avoided, it is frequently used in controlled situations in audio to create certain desirable effects, particularly with electric guitars and amplifiers.
DIY - Refer to Do-It-Yourself
DMM - Refer to Digital Multi-meter
Do-It-For-Me - This refers to customers who use professionals to perform maintenance and repair work on their vehicles, including installation of their mobile electronics product (audio, security, convenience, safety, etc.).
Do-It-Yourself - This refers to consumers who perform maintenance and repair work on their own vehicles, including installing their own mobile electronic equipment.
Dome Light - The common term used to describe the overhead (or headliner) mounted interior courtesy light. The circuit is often a connection point for vehicle security to monitor any entry into the passenger compartment.
Dome Tweeter - a high frequency speaker driver with a dome-shaped diaphragm typically comprised of metal or silk.
Door Lock Solenoid - The proper name for the electric bi-directional actuator used to provide powered control of the vehicle door locks. Also called Door Lock Actuator.
Doppler Sensor - Another name for a spatial type sensor, also commonly called a radar sensor.
Double DIN - So-called "double DIN" receivers are two times the height of DIN-size receivers, which typically works out to 4" tall. These receivers are also shallower in depth and slightly wider. In many cases, these receivers re also equipped with DVD players and navigation systems.
Double Pole Double Throw (DPDT) - A term used to describe a switch or relay that has two separate poles or contacts and can throw or make electrical contact with two separate stationary contacts simultaneously.
DPDT - Refer to Double Pole Double Throw
Dress - The arrangement of signal and wiring for optimum circuit operation, cosmetic appeal, and protective routing. Wiring that is well dressed is neat and orderly and much easier for another installer to sort through when troubleshooting is necessary.
Driver - 1) A transducer in a loudspeaker that converts electrical signals into sound pressure waves. 2) A computer program that controls an attached device or piece of hardware.
DSP - Refer to Digital Sound Processor
DTC - Refer Diagnostic Trouble Code
Dual Band - A wireless phone or mobile communication device that works on more than one spectrum frequency, e.g., in the 800 MHz frequency and 1900 MHz frequency bands.
Dual Mode - A wireless phone or mobile communication device that works on both analog and digital networks.
Dual Reflex Bandpass Enclosure - Bandpass enclosures can be divided into two basic types: single reflex and dual reflex. In a single reflex design the rear chamber is sealed and the front chamber is ported, while in a dual reflex design the front and rear chambers are both ported. The chambers will typically have a simple ratio that helps tune the bandpass of the output frequency of the enclosure, for example a 2:1 or 3:1 ratio.
Dual Voice Coil (DVC) - A dual voice coil driver allows for more wiring configurations. Depending on the application and the impedance of the driver it can be wired up or down to pair with multiple drivers.
DUN - Refer to Dial Up Network
Duty Cycle - An engineering term used to describe the actual time (or frequency) that a circuit or device operates. A pulsing alarm output that is on for seven-tenths of a second and off for three-tenths of a second would have a 70% duty cycle.
DVC - Refer to Dual Voice Coil
Dynamic Range - 1) The ratio (in dB) between the loudest peak and the softest level of a song or recording. 2) The ratio (in dB) between the softest and loudest possible levels a device or system can provide without distortion.