Glossary of Terms

Glossary 
                                              of Terms

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

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. 