Glossary
of Terms
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AC (Alternating Current)
Voltage that alternates from positive to negative in regular or irregular
cycles. This type of voltage flows back to its source. Go Back.
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
Electrical power.
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.
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