DAC D-A

Digital to Analog Converter - Component or circuit that is used to derive or convert an analog signal from a digital one.

Damper

Part of the suspension connected to the bottom of the cone at the voice coil that centers the voice coil in the air gap. It is sometimes referred to as the spider.

Damping

The reduction of the magnitude of resonance by the use of some type of material.

Damping Factor

The ratio of rated load impedance to the internal impedance of an amplifier. The higher the value, the more efficiently an amplifier can control unwanted movement of the speaker coil. A high damping factor is crucial for large speakers that reproduce bass.

DAT

Digital Audio Tape

dB

Decibel - A measurement of sound pressure, or relative intensity of sound. It should be noted that decibels are logarithmic in nature. An increase of 10dB from a certain point represents a doubling of sound output. From an audio standpoint, doubling the sound output of a system will require 10 times the power.

0 dB is the threshold of hearing, 130 dB is the threshold of pain.

Whisper: 15-25 dB

Quiet background: about 35 dB

Normal home or office background: 40-60 dB

Normal speaking voice: 65-70 dB

Orchestral climax: 105 dB

Live Rock music: 120 dB+

Jet aircraft: 140-180 dB

DBO

Dynamic Bass Optimization - A unique active bass EQ circuit that allows the tuning of a subwoofer enclosure after it has been installed into a vehicle.

dBr

A unit of measurement that indicates the decibel level relative to a reference level.

DC

Direct Current. A flow of electrons which travels in one direction only.

DC-AC Converter

A group of components within an amplifier that converts battery voltage (DC) into AC so that it can be increased by the switching devices and transformer and converted back to DC.

DC Resistance

The resistance a device produces for a DC current. Direct measurement by a digital multimeter or a volt/ohm meter gives DC resistance.

Dedicated Fuse

A fuse designated to supply power and protection for one particular circuit only.

Delay

A signal processing device or circuit used to delay one or more of the output signals by a controllable amount. This feature is used to correct for loudspeaker drivers that are mounted such that their points of apparent sound origin (not necessarily their voice coils) are not physically aligned. Good delay circuits are frequency independent, meaning the specified delay is equal for all audio frequencies (constant group delay). Delay circuits based on digital sampling techniques are inherently frequency independent and thus preferred.

Destructive Interference

A phenomenon that occurs when speakers are 180 degrees out of phase, i.e., what one speaker is trying to produce, the other speaker is fighting to cancel. One speaker's wave is in the positive phase (rarefaction), while the other speaker's wave is in the negative phase (compression).

Detachable Face Security

A headunit theft-deterrent system in which the front panel is removable, to prevent its loss.

Diamond Pattern Surround

A patented method that JBL uses to control high-frequency resonance in single-piece titanium speaker diaphragms.

Diaphragm

A thin metal or dielectric disk used as the vibrating member in loudspeakers. Also known as a cone.

Die Cast Aluminum Baskets

Driver baskets that are cast from aluminum. Cast baskets are much stronger than stamped steel and allow for tighter production tolerances and precise driver operation under even the most demanding situations.

Die Cast Basket

A type of speaker basket or frame that is cast as a single piece of relatively thick, rigid metal. This contrasts with a Stamped frame that is shaped by pressure, much like a car body fender. Cast metal is heavier and more rigid, and thus less likely to "ring" at certain frequencies, and will hold its shape somewhat longer against the pull of gravity. This is mainly advantageous in the larger woofers of 12" or greater. Smaller drivers will likely not benefit perceptibly from being cast.

Difference of Potential

The algebraic sum of voltages at two points of different electrical potential.

Differential Input Circuit

A circuit used by JBL amplifiers that re-creates a preamp-level signal from a high-level signal that is of preamp quality. This method produces a signal that is much lower in distortion than the methods commonly used in other amplifiers.

Digital Output

A signal output connection in digital format using TOSLINK connectors.

DIN

Deutsche Industrial Norm. German industrial standardization for radio dimensions, approximately 7 inches wide by 2 inches high. DIN size also refers to the stereo size that fits most European cars.

Diode

An electronic device that blocks current flow in one direction, but allows it in another.

Direct Load

A changer configuration which doesn't use a magazine for the media, instead allowing the insertion of media directly into the unit.

Direct Sound

Sound that arrives at the listeners ear first.. Sound reaching the listening location without reflections, i.e., sound that travels in the most direct path from the source to the listener.

Direct Subwoofer Input

Bypasses the subwoofer's internal crossover to allow the connection of Dolby® Digital (AC-3®) or DTS® receivers and processors that already contain their own subwoofer crossover adjustments.

Discharge

In a capacitor, the release of stored energy to a load. In a battery, the conversion of chemical energy to electrical energy.

Discrete Bi-polar Outputs

An amplifier output wiring scheme employing separate bi-polar type transistors wired in a darlington configuration, offering higher current gain, lower noise and wider bandwidth.

Discrete Circuitry

The use of separate components such as resistors, capacitors, and diodes instead of ICs (Integrated Circuits) which "print" these components in microscopic size on a chip. Discrete components allow for tighter tolerances, and higher performance (especially in amplifier output stages), are less heat sensitive, and make better-sounding components.

Discrete Construction

Circuit construction where the circuit is made up of actual transistors, resistors, diodes and capacitors instead of Integrated Circuits.

Discrete Differential Inputs

An amplifier input wiring scheme employing separate components which comprise the differential input circuit.

Discrete FET-Predrive Stage

An amplifier wiring scheme employing separate Field Effect Transistors in the pre-drive stage for lower distortion and faster switching.

Discrete Final Stage

An amplifier wiring scheme employing separate components in the output stage.

Disc Memo

A Custom File feature that allows the user to assign an eight character name to a disc. Each CD changer has memory for 110 discs.

Disc Title Memory

A feature which enables the user to label their CD’s by programming a 10-digit (varying on brand, make, model) descriptive title per CD.

Dispersion

The extent to which a sound emitter yields acoustic radiation over a given area. This is a particular concern in tweeters and midranges whose portion of the audio spectrum has a much more directional character than woofers. Many Horn tweeters, while very energetic, have a more limited area of dispersion within which their effect can be fully perceived. Generally, Dome tweeters can be heard over a much wider area, all other factors being equal. But each particular example must be assessed individually for this factor. Some radiator designs are better than others.

Displacement

The measurement 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

Sound which is modified or changed in some way. In a speaker, distortion is produced by several things, most related to poor construction. Voice coil rubbing (caused by being overdriven) is the most common cause of distortion.

Diversity Tuner

An FM tuning method which employs two antennas. The tuner can switch between the two antennas in order to attain better reception.

DMM

Digital Multimeter - A digital meter that gives a precise reading of voltage, current, or ohms. This type of meter "samples" the input and feeds it to a digital readout.

Dolby Digital®

Dolby's name for its format for the digital soundtrack system for motion picture playback. Utilizes their AC-3 method of digital compression. The signal is optically printed between the sprocket holes. Introduced to Home Theater on laser disc and DVD and CD. Dolby Digital may use any number of primary audio delivery and reproduction channels, from 1 to 5, and may include a separate bass-only effects channel. The designation "5.1" describes the complete channel format. Surround decoder systems with Dolby Digital automatically contain Dolby Pro Logic processing to ensure full compatibility with the many existing program soundtracks made with Dolby Surround encoding.

Dolby Noise Reduction

Decodes Dolby-encoded cassette tapes during playback to virtually eliminate the tape hiss which is especially apparent in quiet environments. Dolby B is the most widely used system. Dolby C is an extension that is even more effective at increasing the signal-to-noise ratio.

Dome-Tweeter

Tweeters come in several different types; cones, horns and domes being the most popular. Dome types are heavily favored in many standard applications. They are efficient, and have low Distortion and wide dispersion. There is a choice between hard and soft dome materials, but all have relatively low mass and high power handling capabilities.
This same design in a larger form is quite effective as a midrange Driver also, and for many of the same reasons.

Doppler Sensor

Another name for a spatial type sensor, also commonly called radar sensors.

Dot Matrix Display

A display type that employs regularly spaced patterned grids of point-source lighting elements. As a result, characters displayed have greater resolution than a segmented display.

Double DIN

The arrangement of signal leads and wiring for optimum circuit operation, cosmetic appeal, and protective routing.

Double Stacked Magnet

Two magnets overlaying each other to increase the overall magnetic field. In some designs for home theater applications the polarity is reversed which provides the effect of "shielding,"inhibiting the size of the magnetic field radiation, thus allowing the speakers to be used next to a television without creating Distortions on the picture tube. This is achieved without a detrimental effect on the normal power handling capabilities of the speaker.

DPDT

Double Pole Double Throw. A term used to describe a relay that has two separate poles or contacts and can throw or make electrical contact with two separate stationary contacts.2

Driver

Another term for a loudspeaker. Often used when the loudspeaker is coupled to a horn for acoustic coupling and controlled dispersion of sound.An alternate term for: speaker, transducer, or radiator. Technically speaking, the term speaker should refer to an entire sound producing system with whatever combination of woofer, midrange and tweeter; in whatever enclosure type it is housed.

Driver Remote

An ancillary control interface providing intuitive and safe operation of a car stereo.

DSP

Digital Signal Processing - Audio signal manipulation executed entirely in the digital domain.

DSP Control

The ability of a headunit to control an external digital signal processor.

DSP File

A Custom File feature that allows the user to assign a DSP preset to a particular disc, such that when that disc is loaded, the DSP preset is also automatically selected.

DTMF

Dual Tone Multi-Frequency

Dual-Zone

(DVD Players) - Allows you to enjoy two totally different types of media in the front of the car and it the back. Mostly used in systems with DVD players attached.

Dual Channel or Dual Voice Coil Speaker

A woofer with two voice coils mounted to a common cone, which can be connected to separate amplifiers, to produce a common bass output. Since bass has a non-directional character, this still permits the optimum reproduction of the stereo image via other speakers. Care should be taken in making connection, to observe proper polarities, however. Failure to do so can result in the quick extinction of the Driver if the amplifiers are pulling the cone in different directions at once.

Dual Cone

Many factory installed auto speakers are of the dual cone type. Sometimes also referred to as a "full-range" speaker, it uses an inexpensive, efficient design. The small "whizzer" cone in the center of the woofer reproduces high frequencies, but not with the dispersion, range, or intensity of a separate tweeter.

Dual Information Display

A step-up featured display configuration that employs two lines of information; e.g. disc/track data, and clock.

Dual Mode

An amplifier configuration in which both a stereo speaker pair and mono speaker system (usually a subwoofer) are simultaneously powered by a stereo amplifier.

Dual Mono Construction

An amplifier construction configuration where virtually two separate single channels amps are used to comprise a stereo amp. Offers superior crosstalk rejection and channel separation.

Duplexer

A cellular device that permits simultaneous reception and transmission of a call.

Dust Cap

Part of the speaker that keeps foreign material from falling into the voice coil, which could hinder the speaker's movement and cut short its life.

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.

Dv

The inside diameter of a vent or port.

DVD

Digital Versatile Disc - A relatively new standard that seeks to combine better-than-laser-disc quality video with better-than-CD quality audio in a disc the size of a CD. Requires special players.

Dynamic Range

Expressed in decibels, the range of signal amplitudes (from the loudest to the quietest) that can be reproduced effectively by a piece of equipment. With respect to amplifiers, this range is defined by inherent noise at low levels and by overload distortion at high levels. The higher the number the better the performance.

Dynamic Range Suppression

A signal compression technique which raises the level of lower passages without affecting overall volume. Especially useful with high noise levels, such as a moving vehicle.

D Bass

Dynamic Bass. Sony's unique low frequency enhancement system which provides up to 18dB of gain to frequencies below 75 Hz, without midrange coloration or interference.