Glossary of Car Entertainment Terms

27th of January 2009

AC (Alternating Current)

Voltage that alternates from positive to negative in regular or irregular cycles. This type of voltage
flows back to its source.

Acoustics

A science dealing with the production, effects, and transmission of sound waves through various
mediums.

Active Display

A step-up display feature that generates animated patterns for both segment and dot matrix LCDs that
precede the sequential display of information such as clock, Custom File titles, and radio station
frequencies.

Alternator

A device that is turned by a motor to produce AC voltage, which is then rectified (turned into DC) and
used to supply voltage to the vehicle's electrical system.

Alternator Whine

A siren-like whining that appears when the RPMs of an engine increase. The noise is usually the result of
a voltage differential created by more than one ground path or a poor ground path.

Amplification

An increase in signal level, amplitude, or magnitude.

Amperage

A unit of electrical current. The force through which the energy is pushed through a conductor.
Measured in amps.

Ampere

The unit of measurement used to determine the quantity of electricity flowing through a circuit. One
ampere flows through a 1 Ohm resistance when a potential 1 Volt is applied.

Amplifier

A device that strengthens or enlarges an electrical signal.

Amplitude

The measure of how powerful sound waves are in terms of pressure.

Antenna

A mechanical device, such as a rod or wire, which picks up a received signal or radiates a transmitted
signal.

Attenuate

To lessen the amount of force, magnitude, or value of something.

Audio Frequency Spectrum

The band of frequencies extending roughly from 20 Hz to 20 kHz.

Auto Memory

A tuner feature that automatically finds the strongest stations in the local area, and places them in
preset memories.

Baffle

A flat panel that divides the front and rear sound waves produced by a woofer. Sometimes baffle is
used to mean an enclosure or the front panel that the speaker is mounted on.

Balanced Input

An input, which compares the negative and positive sides of the signal, used to help eliminate noise.

Bandpass Filter

In mobile electronics, a device which incorporates both high-pass and low-pass filters in order to limit
and attenuate both ends of the frequency range.

Bandwidth

Refers to the "space" in the frequency response of a device through which audio signals can pass
(between lower and upper frequency limits, those points where the signal level has rolled off 3 dB).

Bass

The part of the frequency range made up of the low frequencies. Bass is generally agreed to be those
frequencies between 20 Hz and 400 Hz.

Bass Reflex

A vented enclosure that allows control of rear radiated sound waves.

Battery

An electrically connected group of cells (wired in series) that stores an electrical charge and supplies a
direct current (DC).

Boomy

Usually refers to excessive bass response, or a peak in the bass response of a recording, playback or
sound reinforcement system.

Bridged

In a multi-channel amplifier, the connection of two channels to drive a single load. The input signal is
split, and then the phase of one of the signals is inverted. The non-inverted signal is sent to the left
amplifier and the inverted signal is sent to the right amplifier (L+R-). The load is connected between the
two outputs so it receives twice the voltage at a given input level. The resultant power is much greater
than the two 4-ohm channels combined.

Butterworth Filter

A filter with a pass-band with no ripple but usually sacrifices some steepness in attenuation.

Capacitance

The property of an electric nonconductor that permits the storage of energy as a result of electric
displacement when opposite surfaces of the nonconductor are maintained at a difference of potential.
In a capacitor, capacitance is the measure of the property (the amount of charge that can be stored)
equal to the ratio of the charge on either surface to the potential difference between the surfaces.

Capacitor

An electronic device which stores energy and releases it when needed. Also used to direct high
frequency energy to tweeters. Rated in Farads.

CD/MD Control

The ability of a component to operate a CD or MD disc changer.

CD Text

A compact disc and player feature utilizing disc, track, and artist information encoded directly on the CD
media. Both playback and media components must have CD Text compatibility.

Circuit Breaker

An electromechanical device designed to quickly break its electrical connection should a short circuit or
overload occur. A circuit breaker is similar to a fuse, except it will rest itself or can be manually rest,
and will again conduct electricity.

Class

There are different classes of amplifiers, depending on how the biasing of the amplifier circuit is done.

Clipping

The distortion that occurs when a power amplifier is overdriven. This can be seen visually on an
oscilloscope, when the peaks of a waveform are flattened, or "clipped of," at the signal's ceiling.

Coaxial Speaker

TA coaxial speaker has a large cone for the low range, and a smaller tweeter for the high spectrum.
There is a cross-over network which divides and routes the signal to the correct driver.

Coil

A number of turns of wire around an iron core or onto a form made of insulating material. Used as an
inductor, a coil offers a great deal of opposition to the passage of AC, but very little to the passage of
DC. This device is good for use as a filter.

Cone

The most common shape for the radiating surface of a loudspeaker. Often used to refer to that part of
the speaker that actually moves the air.

Crossover

A device intended to separate the different frequency bands and redirect them to different
components.

Crossover Frequencies

The frequencies at which a passive or electronic crossover network divides the audio signals, which are
then routed to the appropriate speakers.

Crossover Network

A unit which divides the audio spectrum into two or more frequency bands (Also see Crossover
Frequencies).

Current

The rate of electrical or electron flow through a conductor between objects of opposite charge. Symbol
I, measured in amperes or amps.

DAC (D/A)

Digital to analog converter. A component or circuit that is used to derive or convert an analog signal
from a digital one.

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.

dB (Decibel)

The unit of measurement for sound, using a logarithmic scale. It is an expression of the relative
loudness of a sound or power level.

DC (Direct Current)

A flow of electrons which travels in one direction only.

Detachable Face Security

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

Digital Output

A signal output connection in digital format using TOSLINK connectors.

Digital Signal Processing

Audio signal manipulation executed entirely in the digital domain.

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.

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.

Driver

Another term for a loudspeaker. Often used when the loudspeaker is coupled to a horn for acoustic
coupling and controlled dispersion of sound.

DSP Digital Signal Processing (or Processor)

A type of processing accomplished by a microcomputer chip specifically designed for signal
manipulation, or a component using such processing. The term is often misused as a synonym for
ambience synthesizer; however, DSP can do much more than sound field creation.

DSP

Control the ability of a head unit to control an external digital signal processor.

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.

DVC Subwoofer

Refers to a subwoofer with 2 voice coils. These coils can be any impedance. Allows for a wider range of
installation options.

Efficiency

The measure of loudspeaker's ability to convert power to work. Formula Efficiency = (power
out/power in) x 100. Efficiency is always expressed as a percentage.

Electrolytic Capacitor

A capacitor with a negative and a positive terminal that only passes alternating current.

Enclosure

A box housing a speaker to separate the front sound waves from those in the rear.

Farad (F)

The basic unit of capacitance. A capacitor has a capacitance of 1F when a charge of 1 Volt across the
capacitor produces a current of 1 Ampere through it.

Fidelity

A term used to describe the accuracy of recording, reproduction, or general quality of audio processing.

Flat Response

An output signal in which fundamental frequencies and harmonics are in the same proportion as those
of the input signal being amplified. A flat frequency response would exhibit relatively equal response to
all fixed-point frequencies within a given spectrum.

Fluttery

A Bass response often cause by the subwoofer's enclosure being larger than it is rated x-max. To
much air allows the subwoofers to flutter uncontrollable. Often an EQ can help this.

Fold Down Face

A DIN head unit whose faceplate hinges at the bottom to reveal a media-loading slot. Provides a larger
area on the face for the display and controls.

Free Air Response

The frequency at which a speaker will naturally resonate.

Frequency

The term in physics, that refers to a number of vibrations or cycles that occur within a given time.

Frequency Modulation (FM)

A method of modulation in which the frequency of the carrier voltage is varied with the frequency of
the modulation voltage (Also see Amplitude Modulation).

Frequency Response

A term which describes the relationship between a devices is input and output with regard to signal
frequency and amplitude.

Full Logic Deck

A cassette mechanism where the tape operations are carried out by logic circuits rather than
mechanical methods.

Fuse

A device designed to provide protection for a given circuit or device by physically opening the circuit.
Fuses are rated by their amperage and are designed to blow or open when the current being drawn
through it exceeds its design rating.

Gain

Refers to the degree of signal amplification.

Ground

The term given to anything having an electrical potential of zero. Most modern vehicles are designed
around a negative ground system, with the metal frame being the vehicle's ground.

Ground Loop

The term given to the condition that occurs when a voltage potential exists between two separate
ground points.

Harmonic

A weaker overtone or undertone of the original note responsible for the character of the note.

Heat Dissipation

The ability to transfer heat away from a component into the air to prevent damage to the speaker.

Heat Sink

Part of the frame of the speaker used to conduct and radiate heat away from the motor assembly.

Hertz (Hz)

The unit of frequency within a specific period, such as alternating or pulsating current; 1 Hz = 1 cycle
per second.

High Frequency

Refers to radio frequencies in the 3-30 MHz band. In audio, it usually refers to frequencies in the 5-10
kHz band.

High Level

Input An input configured to accept speaker level signals.

High Pass Filter (HPF)

A network of components, which attenuate all frequencies below a predetermined frequency selected
by the designer. Frequencies above cut-off are passed without any effect.

High Power Output

Speaker level outputs driven by an amplifier, typically at least 35 watts max per channel.

Imaging

The effect of reproducing a sound stage faithful to that of an original recording. Represented, for
instance, in the listener's ability to place a particular instrument at a single point, rather than to hear it
as if spread throughout the sound field. Good imaging is often described in terms of channel separation
of openness.

Impedance (Audio)

A measurement of the resistance to the audio current by the voice coil of the speaker.

In-Line Fuse

A fuse and holder incorporated into a length of supply wire.

Inductor

An electrical component in which impedance increases as the frequency of the AC decreases. Also
known as coils that are used in passive crossovers. Inductors are rated in Henries.

Infinite Baffle

A loudspeaker baffle of infinite space that has no openings for the passage of sound from the front to
the back of the speaker. Also, a sealed enclosure where the internal volume is greater than the Vas of
the driver.

ISO-DIN Mounting

Refers to a mounting system in which the head unit is mounted behind the dash panel with side
brackets, employing factory installed trim panels.

kHz

Abbreviation for kilohertz, or 1000 cycles per second.

LCD

Liquid Crystal Display.

LED(s)

Light-Emitting Diodes. A form of diode that sheds light. Used in many systems for indicator purposes.

Load

The resistance or impedance to which energy is being supplied. In amplifiers, the speaker or speakers
connected to the output of the amplifier.

Loudness

A signal-processing feature, which compensates for the human ear's deficiencies at various listening
levels.

Loudspeaker

An electro-acoustic transducer that converts electrical audio signals at its input to audible sound waves
at its output.

Low Pass Filter

A network of components which attenuate all frequencies above a predetermined frequency selected
by the designer. Frequencies below cut-off are passed without any effect.

Memory

The word most commonly used to refer to a system's ability to retain specific information.

Midrange Driver

A loudspeaker specifically designed to reproduce the frequency in the middle of the audible bandwidth.
Most musical energy lies in the mid band.

Mono

The operation of an amplifier in one channel for both input and output. Can refer to an amplifier with
only one channel of amplification.

MOSFET (Metal Oxide Semiconductor-Field Effect Transistor)

A form of field-effect transistor controlled by voltage rather than current, like a bipolar transistor.
MOSFETs have a significantly higher switching speed than bipolar transistors. They generate almost no
loss (little heat generation), which lends the power supply fast response, excellent linearity, and high
efficiency.

Neodymium Magnet

A magnet material offering 7.5 times the magnetic strength of standard magnetic materials.

Nominal Impedance

The minimum impedance a loudspeaker presents to an amplifier, directly related to the power the
speaker can extract from the amplifier.

Octave

A musical interval between two tones formed when the ratio between the frequencies of the tone is
21.

Ohm

Electrical resistance equal to the resistance of a circuit in which an electromotive force of one volt
maintains a current of one ampere.

Parallel

A circuit in which two or more devices are connected to the same source of voltage, sharing a
common positive and negative point, so that each device receives the full-applied voltage.

Parametric EQ

An equalizer with adjustable frequency, level, and "Q".

Passive Component

In a crossover system, a non-powered component used to separate an audio signal into a specified
frequency band before it goes to a particular amplifier or driver. A passive device usually presents some
loss (expressed in decibels) to a system.

Phase

The timing of a sound wave that is measured in degrees from 0 to 360.

Polarity

In electricity, refers to the condition of being either positive or negative.

Power

The amount of energy (in joules) that a device delivers or consumes divided by the time (in seconds)
that the device is operating.

Pre-Amp

A circuit unit which takes a small signal and amplifies it sufficiently to be fed into the power amplifier for
further amplification. A pre-amp includes all of the controls for regulating tone, volume, and channel
balance.

Preamp Output

Typically found on head units, a preamp output provides low level, high quality audio signal for use with
external amplifiers.

Preset

A collection of system settings stored in a memory that is virtually instantly recallable, typically at the
touch of a button.

Receiver

A device designed to receive a signal or command from a source such as a transmitter.
Resistance

The electrical term used to describe the property that various materials possess to restrict or inhibit the
flow of electricity. Electrical resistance is relatively low in most metals and relatively high in most
nonmetallic substances. Electrical resistance is measured in ohms.

Resonant Frequency

The frequency at which a speaker cone vibrates the easiest-the point at which it has the most
amplitude.

RF Modulator

A device that converts a signal (typically audio and/or video) into a radio frequency.

RMS (Root Mean Square)

Generally a closer representation of output power of an amplifier -vs- Peak Power.

Sensitivity

The rating of a loudspeaker that indicates the level of a sound intensity that the speaker produces (in
dB) at a distance of one meter when it receives one watt of input power.

Signal to Noise Ratio

A ratio which indicates how much audio signal there is in relation to noise, or a specified noise floor.

Sound

A type of physical kinetic energy called acoustical energy (Also see Acoustical Energy).

Sound Pressure Level (SPL)

An acoustic measurement for the ratios of sound energy. Rated in decibels (SPL dBA, SPL dBC).

Spectrum Analyzer

A device that displays a frequency response curve, in real time, as the curve, changes.

Strontium Magnet

A magnetic material with superior magnetic strength characteristics to that of ferrite.

Subwoofer

A loudspeaker made specifically to reproduce the lowest of audio frequencies, approximately between
45 Hz and 125 Hz.

THD (Total Harmonic Distortion)

A component specification which describes its ability to accurately reproduce a signal. Although lower
numbers are considered to be better, the human ear typically cannot detect THD ratings below 2% or
3%.

Tweeter

A small loudspeaker or driver meant to reproduce treble frequencies.

Vented Enclosure

A type of speaker enclosure with a vent (or port). The combination of (1) the specific internal volume
of air and 2) the action of the port allowing some sound waves from the enclosure's interior to pass
through, enhances the speaker's response.

Voice Coil

A coil of wire and the former (bobbin) around which the wire is wound. It is part of a speaker's
electromagnetic motor that drives the cone to produce sound waves.

Voltage

Electromotive pressure that forces current through an electrical conductor. The difference of potential
between any two conductors of a circuit.

Watt

The basic practical unit of measure for electrical or acoustical power.
Wattage

Woofer

A large dynamic loudspeaker that is well suited for reproducing bass frequencies.

Xmax

The distance a speaker cone can travel before the magnet loses control over the voice coil.