Car Stereo Terminology

Car Audio & 12v Terminology


This article aims to be a reference dictionary / glossary to most of the common as well as many special 12v terms used in car audio and electronics. The article contains more than 350 definitions to various terms on a basic level.

Although the basic knowledge of Math and Physics becomes necessary to understand all the terms mentioned here.

There may be many instances where it becomes necessary to use terms which shall appear later as per the alphabetical order. A cross reference shall help you gain a proper understanding.

An in-depth understanding of these terms and their application shall prove very helpful to any car audio enthusiasts.

A

•Accessory (position) - Refers to the position of the key in the ignition switch; a wire showing 12 Volts (+) when in this position.
•Acoustic Absorption - The sound deadening properties of any substance, measured in Sabine units. One Sabine is equal to the absorption of 1 square foot of surface which will absorb all incident energy.
•Acoustic Feedback - A squealing sound when the output of an audio circuit is fed back in phase into the circuit's input.
•Acoustics - The study of sound. The science of production, effects, and transmission of sound waves through various mediums and the effects of absorption, diffraction, interference, reflection, and refraction.
•Aliasing Noise - The result of the sampling frequency not being at least double the highest analog frequency during the digital encoding of an analog signal.
•Alternate-Channel Selectivity - A measurement of a tuner's ability to select one radio station's signal and reject the signal of another radio station two channels (0.4 MHz) away. Measured in decibels, the higher the number the better.
•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 RPM’s 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.
•Alternating Current (AC) - An electric current that reverses direction at regular intervals. Measured in Volts AC at Hertz, example: 110 volts AC 60 Hz.
• Ambience Synthesizer - A unit that produces an artificial ambience pattern; one that is used to create the impression of the listener and/or performer being in a particular performance space.
•American Wire Gauge (AWG) - A standard of the dimensional characteristics of wire used to conduct electrical current or signals. AWG is identical to the Brown and Sharpe (B & S) wire gauge.
•Ammeter - An instrument that measures the magnitude of an electric current in amperes.
•Ampere (amp) - A unit that defines the rate of flow of electricity (current) in a circuit. •Amplification - The increase in signal level, amplitude or magnitude.
•Amplifier - 1 A device which increases the level of a signal by increasing the current or voltage. 2 May also be used to isolate or control a signal and even decrease the level as in a line output converter.
•Amplifier, Power - An amplifier designed for driving loudspeakers and having a higher power output than a line amplifier or preamplifier.
•Amplitude - The maximum value of a periodically varying quantity.
•Amplitude Modulation (AM) - The encoding of a carrier wave by variation of it's amplitude in accordance with an input signal.
•AMS - Automatic Music Search. A feature that allows a CD or cassette mechanism to skip forward or backwards to another track.
•Analog - A way to represent data by means of continuously variable quantities. A control or circuit which continuously changes the level of a signal in direct relationship to the control setting. An electrical signal whose frequency and level vary continuously in direct relationship to the original acoustical sound waves. (Something that is analogous) •Analog to Digital Converter (ADC) - A circuit that converts an analog signal into a digital signal. With a continuous input signal the ADC will check the signal several time per second (sampling), assign values to the samples and represent it as a binary number (quantization and encoding).
•Analogous - Alike in certain ways. Similar in function, but not in origin or structure. •Antenna - An apparatus used for sending and receiving radio waves, usually constructed of metal. The mast can be fiberglass, a polymer or metallic. It is often tuned to maximize maximum signal input/output at a specified carrier frequency. (Or bandwidth)
•Antenna Trimmer - An adjustment found on analog radios used to maximize AM reception. Turning this trimmer to the point where the sound is the loudest increases the sets signal to noise ratio optimizing performance.
•Anode - The electrically positive pole of an electronic device such as a semiconductor. A diode, for instance, has a positive and a negative pole; these are known as the anode and the cathode.
•Arm - The term used to describe the act of causing a security system to reach a state in which it will protect the vehicle.
•Arming Delay - A term used to describe the elapsed time between the moment a security system is first told to arm, and when it is actually armed. This normally only applies to systems that are passively armed, but can apply to actively armed systems as well. (Also see Exit Delay).
•ATA - Automatic Tuner Activation. A feature that allows the tuner to be accessed while a tape deck is rewinding or fast forwarding.
•ATRAC - Adaptive Transform Acoustic Coding. The process used in MiniDisc that utilizes psychoacoustic principles to limit quantization noise and reduce the data quantity from 16 bits to 4 bits by using non-uniform frequency and time division.
•Attenuator - An active or passive device to decrease or increase the strength of a signal.
•Audible Frequency – The acoustic spectrum of human hearing, generally regarded to be between 20Hz and 20 kHz.
•Audio Oscillator - A device that produces tones at specific frequencies for testing either equipment or entire systems.
•Auto Eject - Feature of a cassette player that ejects the tape when it has finished playing one side.
•Auto Loud - Automatically provides low frequency & high frequency boost for listening at low levels. •Auto Replay - Feature of a cassette player that automatically rewinds a tape when it has reached the end of one side, then begins to replay.
•Auto Reverse - Feature of a cassette player that automatically plays the reverse side of a tape when one side has reached the end.
•Auto Stop - Feature of a cassette player that automatically shuts off power when a tape has reached the end of either side in any mode.
•Automatic Gain Control (AGC) - A circuit that continuously adjusts the recording amplifier gain to maintain a relatively constant recording level.
•Azimuth - The perpendicular alignment of the tape to the head of a tape player / recorder. (Can be adjusted if audio/video signals are missing, distorted or not optimal)

B

•B - Magnetic flux density in gap, in Tesla-meters (TM)
•Balance - The relative volume level between two channels, usually the left and right channels. May also refer to the relative volume between front and rear channels of an audio system. To make the same or equal.
•Baffle – A board or any other planar surface used to mount a loudspeaker.
•Band pass - A two-part filter that cuts both high and low frequencies allowing the band of frequencies between these two points to pass.
•Band pass Enclosure – Type of enclosure used sub-woofers where the driver is completely inside the enclosure and all the output emerges through a Port(s). This configuration is usually designed for high output volume at particular frequency band with less importance to accuracy and fidelity.
•Bandwidth - The range of frequency response between lower and upper frequencies points which audio signals pass through an electrical device or conductor where the signal has rolled off by three decibels.
•Barium Ferrite - A speaker magnet material made from an alloy with iron and barium for improved magnetic strength.
•Basket - The rigid frame of a speaker that supports all of it's components.
•Bass - The low audio frequency range typically below 300 Hz (hertz).
• 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).
•BBE Processing - A signal processing circuit that provides improvements in imaging and spatial realism by altering the frequency and phase characteristics of portions of the input signal.
•Bessel Alignment - A particular crossover configuration which offers superior phase coherence in exchange for slightly lower level match.
•Bi-Amplification - The use of two amplifiers, one for the amplification of lower (bass) frequencies , and the other for higher (midrange and treble) frequencies. The audio signal from the head unit or pre-amplifier is passed through an electronic crossover and divided into two separated signals. These signals are sent to the respective amplifiers and their outputs are sent to the respective speakers. (Bass to woofers, midrange and treble to mids and tweeters through the use of passive crossovers) Tri-Amp is the use of three amplifiers in the same manner with the audio signal divided into three separate bands of frequency by the electronic crossover and so on.
•Bias - A necessary high frequency current applied to the record head along with the audio signal to prevent distortion and increase sensitivity during recording.
•Binary Digit (BIT) - The smallest unit of data in a digital signal represented by either a one or zero.
•Bi-polar Transistor - A transistor that contains two p or n junctions or diodes between two layers of opposite POLARITY material (emitter and collector) .
•BL - The magnetic strength of the motor structure.
•Blank Skip - A cassette feature that automatically detects blank areas of the tape over 8 seconds in length and activates Fast Forward, until the end of either the tape or audio information is reached.
•Boom, Boomy - Excessive bass response or peak in bass response of a recording, playback, or sound system. Dominant in the low frequency range. Without complimentary levels of frequencies other than bass.
•Boost - To Increase signal strength of a given audio input.
•Bottom End - Bass response; referring to the sound qualities of the lowest frequency ranges of a speaker or audio system.
•Bridging - Combining two outputs of an amplifier to use as one, usually to a woofer. The provides an increase in power output (wattage) necessary to reproduce lower frequencies at higher volume levels.
•Brown and Sharp Gauge(B & S Gauge) - A standard of the dimensional characteristics of wire used to conduct electrical current or signals. B & S Gauge is identical to the American Wire Gauge (AWG).
•BTL - Bridged, Transformer Less. A circuit design wherein two small Integrated Circuit (IC) amplifier channels are bridged together to provide a single, larger output circuit. These circuits are limited by their current capabilities and the amount of heat they generate.
•BTM - Best Tuning Memory. A feature in which the tuner selects radio stations by signal strength, and assigns them to presets in numerical order, according to their frequency value.
•Buffer - Commonly found in Mini Disc (MD) and Compact Disc (CD) players, this device protects against vibrations by storing the audio data for uninterrupted playback. Data is available from the buffer when it can not be read from the disc so long as the interruption of reading the disc does not exceed the playback time of the data stored in the buffer.
•Burr-Brown D/A converter - A high-end D/A converter offering superior sound quality and performance. "Burr-Brown is the manufacturer's name.
•Butterworth Filter - A filter with a pass-band with no ripple but usually sacrifices some steepness in attenuation.
•Byte - Eight bits. It takes one byte to represent one letter of the alphabet in computer code.






C

•C - Propagation velocity of sound at STP, approx. 342 m/s
•Cas - Acoustical equivalent of Cms
•Cmes - The electrical capacitive equivalent of Mms, in farads
•Cms - The driver's mechanical compliance (reciprocal of stiffness), in m/N
•Capacitance - The ability of a conductor or dielectric to store electric charge. •Capacitor - 1 (polarized) an electrical circuit element used to store charge temporarily, consisting in general of two metallic plates separated by a dielectric. 2 (non-polarized) A crossover component used to filter out lower frequencies and allow higher frequencies to pass. 3. A short term power storage device that releases stored power when triggered. It then needs to be refreshed after discharge.
•Capture Ratio - Expressed in decibels, with the smaller the number the better. The ratio of captured signals of different strength on the same frequency.
•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.
•Cell - A single uni8t for producing DC electricity by electromechanical or biomechanical action. A common vehicle battery is composed of a number of individual cells connected together. Each cell is typically rated at 2.11 Volts each, and a common 12V-DC automotive battery is composed of 6 separate, 2 Volt cells connected in series.
•Center Run Wire Path - (Center Path Wiring) A method of running wires to the midrange/tweeter bridge in a coaxial speaker. Actual copper wire (instead of tinsel leads) are run through a hole drilled in the magnet. This offers better signal transfer and efficiency.
•Channel - A frequency or band of frequencies assigned to a station or communications system. Also, a sub-circuit of a larger system, i.e., voice channel, control channel, paging channel, etc.
•Chassis - The metal frame of the vehicle.
•Chebyshev Filter - A filter that has some ripple in the pass-band but has an initial •Chirp - attenuation slope which is steeper than a Butterworth filter.
The term used to describe the brief sounding of a security system's siren designed to indicate the state of arm of the system.
•Circuit – 1. Any closed path followed by electrical current. 2. A configuration of electrically or electromagnetically connected components or devices.
•Circuit Breaker - A device that protects electric circuits by interrupting power in a circuit when an overload occurs. Unlike a fuse a circuit breaker, it can be reset manually of automatically, depending on design. Rated in amperes (amps).
•Clipping - Audible distortion that occurs when continuous power-to-peak power capabilities (headroom) are exceeded. "Turn it down!"
•Coaxial - A speaker composed of larger cone for low range frequencies and a smaller cone or tweeter for higher frequencies aligned on the same axis. A crossover network is necessary to route the proper signals to each driver. These may be passive (usually included). If the speakers are bi-amplified, an active crossover will be used to route the proper range of frequencies to the respective amplifier channels.
•Coil (Choke, Inductor) - A crossover component used to filter out higher frequencies and allow lower frequencies to pass.
•Coloration – Any change in the characteristics of sound that reduces naturalness, such as an over emphasis of certain tones or frequencies.
•Compliance - The measurement in liters or cubic feet of the volume of air that is equal to the compliance of a speaker's total suspension.
•Conduction - The mode of heat transfer within a body or between bodies in contact with each other.
•Conductivity - The ability of a conductor to allow the passage of electrons, measured in the current per unit of voltage applied, shown in resistance.
•Cone - The most common shape for the radiating surface of a loudspeaker referred to as the part that moves the air.
•Constant 12 V (+) - A lead, wire, or connection point that shows positive 12 volts regardless of ignition key position or any other switch; Positive terminal of 12 volt battery.
•Continuity - The condition of being continuous. - The condition of being continuous. A closed circuit between power source and load. (An electronic testing device like an ohm meter or closed circuit test lamp)
•Cross Interleave Reed-Solomon Code (CIRC) - A combination of codes and interleaved data that make it possible to detect and correct errors in a compact disc system.
•Crossover Frequencies - The frequencies at which an active or passive crossover network divides audio signals, expressed in Hertz (Hz).
•Crossover Network - A unit that divides the audio spectrum into two or more frequency bands. The two types are active and passive.
•Crossover Point - Same as crossover frequency.
•Crosstalk (Channel Separation) - The amount of interference on one stereo channel caused by the leaking of the other stereo channel. The higher the rating in decibels (dB), the better the Channel Separation.
•Current - The rate of flow of electricity, measured in amperes (amps).

D

•D - Effective diameter of driver, in meters
•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 movement of a speaker cone, due to either the electromechanical characteristics of a speaker driver suspension, the effects of frictional losses inside a speaker, and/or by electrical means.
•Damping Factor – This is the quantity which defines how quickly the amplifier can stop a reproduced frequency such as a bass note. The higher the Damping factor the better the amp will control the woofer and help reduce overhang distortion. The damping factor of an amplifier is mostly dependent on the quality of the power supply which feeds the power amp.
•Damping material – Any material added to the interior of a speaker enclosure to absorb sound and reduce out-of-phase reflection to the driver diaphragm (cone). Usually acoustic fiberglass, polyester batting or polyfill is used in speaker enclosures.
•Decade - A measurement equal to the low pass frequency being ten times the high pass frequency, which is relevant in a passive band pass crossover. The difference between 500 Hz and 5000 Hz is equal to 1 decade.
•Decibel (dB) - A unit of measurement for the ratio of loudness. The threshold of hearing is 0 dB. One dB SPL is the smallest audible difference in sound level.
•Detent Controls - A detent knob has precise click-stops at regular points to indicate how much the control has been turned up or down.
•Detachable Face Security - A head unit theft-deterrent system in which the front panel is removable, to prevent its loss.
•Deutsche Industrie Normen (DIN) - German (European) industrial standards. DIN size refers to the stereo size that fits most European automobiles.
•Diaphragm - A thin metal or dielectric disk used as the vibrating member in loudspeakers. Also known as a cone.
•Dielectric - An insulating material with low electrical conductivity.
•Diffusion – The scattering of sound.
•Diffraction – A change in the direction of a sound wave, caused by hitting an obstacle or another sound wave.
•Digital Output - An output where the signal is in digital form to allow external processing before being converted to an analog signal.
•Digital Time Delay - A component that electronically delays the audio signals (in milliseconds) to provide surround type sound as well as compensate for speaker placements.
•Digital Time Delay Gain Control - The control that lets you select how much of the whole of the audio signal to be treated with digital time delay.
•Diode - An electrical circuit element that allows current to flow in one direction. •Direct Current (DC) - An electrical current that flows in one direction. . A battery is a common source of DC power. It has fixed 2 poles. One is positive, the other is negative.
•Directional / Directionality - The angle at which a speaker disperses sound. Higher frequencies are narrower than lower frequencies. Tweeters are more directional than woofers.
•Disc memo - A Custom File feature that allows the user to assign an eight character name to a disc.
•Discharge - In a capacitor, the release of stored energy to a load. In a battery, the conversion of chemical energy to electrical energy.
•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.
•Dispersion - Distribution angle or polar output of sound waves from a speaker.
•Distortion - Sound that is modified or changed in some way. Measured as a percentage of the whole signal.
•Dolby Noise Reduction - A patented noise reduction system that increases dynamic range and signal-to-noise ratio of Dolby encoded media.
•Dome - A convex speaker shape usually used for tweeters.
•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 - Twice the height of the standard DIN dimensions.
•Driver - Synonymous with loudspeaker. The term also refers to a loudspeaker being 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.
•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.
•Dynamic Noise Reduction (DNR) - A signal-processing circuit that reduces the level of high frequencies (hiss). Unlike Dolby Noise Reduction, DNR does not require processing during recording.
•Dynamic Range - The difference between the softest and loudest portions of sound that an amplifier or recorder can reproduce within an acceptable range of distortion. Expressed in decibels, the higher the number the better.

E

•Effects Loop - A signal path which allows an audio processor to be switched in and out of the signal path such as an equalizer. (Reverb, time delayed echo etc.)
•Efficiency - The ratio of energy output to total energy input, expressed as a percentage. With speakers, this refers to the ratio of total acoustic watts radiated to total electrical watts input.
•Efficiency Rating - The loud speaker parameter that shows the level of sound output when measured at a prescribed distance with a standard level of power fed into the speaker, usually recorded at 0 dB reference level @ 2.83V input at a distance of 1 meter or 1watt/meter.
•EL-Backlight - Electro-Luminescent illumination for the lighted portion of a liquid crystal display. Considered to be a step-up featured display.
•Electrolyte - The name for the mixture of diluted sulfuric acid found in standard lead-acid vehicle storage batteries.
•Electromagnetic Field - A field of magnetic energy in the woofer's voice coil created by the audio signal passing through the wire.
•Electromagnetic Interference (EMI) - The interference caused by an electromagnetic field created by the flow of current.
•Electronic Crossover – A type of frequency filter which uses active circuitry along with passive components to filter out the desired frequencies.
•Electrostatic Loudspeaker - A speaker composed of two pieces of metallic foil separated by a sheet of dielectric unlike a cone and voice coil of a typical cone-type speaker.
•Enclosure - A box that contains the driver (speaker).
•Enhanced Protection Circuitry - A feature designed to help prevent a device from voltage, current, and temperature faults.
•EQ file - A Custom File feature that allows a user to assign a equalization curve preset to a particular disc, such that when the disc is loaded, that EQ preset is selected automatically.
•Equalization - The process of changing the frequency balance of a signal so acoustical energy is proportional to the electrical input (or any type of relative frequency adjustment).
•Equalizer - A component designed to alter the frequency balance of an audio signal.

F

•F3 -3 dB cutoff frequency, in Hz
•Fader - The control that adjusts the relative volume levels of front and rear speakers in a four speaker system or the front and rear pre-amplifier outputs.
•Farad - The basic unit of capacitance. A capacitor has a value of one farad when it can store one coulomb of charge with one volt across it.
•Fb Enclosure resonance (usually for bass reflex systems), in Hz
•Fc System resonance (usually for sealed box systems), in Hz
•Fidelity - The term used to describe the accuracy of recording, reproduction, or general quality of audio processing.
•FL Backlight - Fluorescent illumination for the lighted portion of a liquid crystal display. Considered to be a step-up feature from EL backlight.
•Filter - An active or passive circuit or device designed to block a certain frequency or range of frequencies.
•Flat Frequency Response - Term for a circuit or audio system which will pass audio signals that will vary by no more than ± 1 dB usually between 20 Hz and 20 kHz unless otherwise specified.
•Fletcher Munson Curves - The set of curves showing the human's ear's frequency sensitivity versus loudness, created by researchers Fletcher and Munson. The curves show the ear to be most sensitive to sounds between 3 kHz and 4 kHz (ear canal resonances).
•Floating Ground - Non-common grounding point. Often used in car audio systems where speakers are grounded to the HU independently of the vehicle grounding system.
•Flux - The flow of magnetic energy in a circuit.
•FM - A method of modulation in which the frequency of the carrier voltage is varied with the frequency of the modulation voltage
•FM Stereo Separation - The FM tuner demodulator's ability to separate left and right channel signals of FM stereo broadcast. Measured in decibels, the higher the number the better.
•Foam Surround - A speaker surround design employing a foam material for improved durability and performance.
•Focus Lens - The lens in the optical block of a compact disc player which focuses the laser light onto the surface of the disc.
•Focus Servo - The circuit which keeps the laser light correctly focused on the pit area of the disc.
•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.
•Former - The cylinder portion of a speaker's voice coil; the wire is wound around this cylinder to form a coil.
•Free Air Resonance – The natural resonant frequency of a driver when operating outside an enclosure.
•Frequency - The number of wavelengths which pass a specific point in a specific time period, measured in Hertz (Hz). Cycles per second.
•Frequency Dividing Network - See ‘crossover network.’
•Frequency Modulation (FM) - The encoding of a carrier wave by variation of it's frequency in accordance with an input signal.
•Frequency Response - The lowest and highest parts of the frequency spectrum that can be reproduced by an audio component within specific limits and tolerances.
•Fs Driver free air resonance, in Hz. This is the point at which driver impedance is maximum.
•Full Range Driver(speaker) – A speaker designed to produce all or most of the sound spectrum within the human hearing, i.e. 20Hz to 20 kHz.
•Full Logic Deck - A cassette mechanism where the tape operations are carried out by logic circuits rather than mechanical methods.
•Fundamental Frequency – The tone produced by the lowest frequency component of an audio signal. This is the primary tone without any additional harmonic overtones.
•Fuse - A device that protects electric circuits by interrupting power in a circuit when an overload occurs. Rated in amperes (amps).

G

•Gain - The amount of amplification used in an electrical amplifier circuit.
•Gauge (wire) - The diameter of a wire. The higher the number, the thinner the wire. •Graphic (equalizer) - Refers to a type of equalizer with sliding controls that create a pattern representing a graph of frequency response changes.
•Ground - An electrical line with the same electrical potential as the chassis of the vehicle, most commonly negative 12 volts DC.
•Ground Loop - The condition created when two or more return paths for electricity are created in a ground line, or when one or more grounding paths are created in a shielded audio cable. The ground lines are not at true ground reference levels. This can create undesirable noise such as a high pitched whine when the vehicle is running or pops and clicks when other devices are used in the vehicle.
•Ground Potential - In an automobile this is the electrical potential of the vehicles chassis, specifically the chassis of the alternator when the vehicle is running. A circuit, terminal or chassis is said to be at ground potential when it is used as a reference point for other potentials in the system.
•Group Delay – It is a measurement of the average delay of the filter as a function of frequency. It is the negative first derivative of the filters phase response.



H

•Harmonics - The multiple frequencies of a given sound, created by the interaction of signal waveforms.
•Harmonic distortion – Harmonics artificially added by an electrical circuit or speaker, and are generally undesirable. It is expressed as a percentage of the original signal. See ‘THD’.
•Harness - The universal name for a bundle or loom of wires that compose the wiring for a system.
•Heat Dissipation - The ability to transfer heat away from a component into the air to prevent damage.
•Heat Sink - Part of the frame of the amplifier or speaker used to conduct and radiate heat away.
•Henry / Henries (Hy) - The measurement for inductance. Coils (low pass filters) are measured in milli henries as in 6.4 mHy (6.4 millihenries).
•Hertz (Hz) - The unit of measurement for frequency. 1 Hz is equal to 1 cycle per second.
•High Frequency Driver - A loudspeaker specifically designed to reproduce short, high-frequency wave lengths. The driver typically has a small, lightweight diaphragm. Tweeter.
•High Level Input - An input configured to accept speaker level signals.
•High Pass Filter (HPF) - A network of elements used to attenuate all frequencies below a predetermined frequency. Frequencies above the cutoff point pass without any effect. •Highs - Term which refers to a set of speaker components used to reproduce frequencies above 500 Hz as in a set of separates. May also refer to tweeters which are used to reproduce frequencies usually above 2.5 kHz. Not bass or midrange frequencies.
•Hiss - Background audio noise often associated with tape audio formats. Most noticeable at low signal levels and high gain amplification.
•Horn(s) - A speaker designed using its own funnel shaped conduit to amplify, disperse of modify the sounds generated by the internal diaphragm of the speaker.
•Hum - An audio noise that has a steady low frequency pitch. Often associated with ground loop issues or poor filtering capacitors in preamp or amplifier circuits


I

•IASCA - International Auto Sound Challenge Association.
•Ignition Power - Refers to a source of power in the vehicle, controlled by the ignition switch, that has +12VDC on it when the ignition key is both in the run and start positions. •Image Rejection - The rejection of the same signals that can be received at two or more points on the dial of a tuner by a single radio station (ghosting, false images). Image Rejection is expressed in decibels, the higher the number the better.
•Imaging - The reproduction of sound accurately so that the listener can imagine the original environment and placement of the original sound sources accurately within that environment. The better the imaging the more analogous the reproduced sound will be to the original event via recording.
•Impedance - The opposition to the flow of alternating current (AC) in a circuit. Measured in Ohms . (Omega is the Greek symbol for ohms).
•Inductance - The ability to induce an electrical current. Measured in Henrys.
•Infrasonic (Sub-sonic) Filter – A filter designed to remove extremely low frequencies inaudible by the human ear, usually between 0 to 25Hz.
•Infinite Baffle – A flat surface that completely isolates the back wave of a driver from the front.
•Input – Connection from signal source. (a guitar or microphone) to a preamp and amplifier.
•Input Sensitivity Control - Adjusts the amount of input signal being fed to the amplifier stage to reduce distortion.
•Insulation - A material that electrically isolates a conductor or thermally isolates an object from its surroundings.

•Inter-modulation Distortion (in loudspeakers) - Is the distortion generated in single cone speakers when the cone is reproducing a high and low frequency simultaneously. The high frequency peaks will be flattened off if the low frequency is distorted in any way.
•Inverter - Takes the input signal and applies a 180º phase shift.
•Isobaric Enclosure – Enclosure where one woofer is buried in the enclosure and the other is mounted up against the first and wired in reverse polarity. There are many variations to this design.
•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.
•Isolation - Electrical or acoustical separation to prevent the spread of noise and the effect on the signal of unwanted elements produced by internal or external devices.

J

•Jacket - The outer covering on a cable or wire that may provide electrical insulation and/or resistance to abrasion, chemicals, and moisture.
•Jams - Tunes, rocks, hits, sounds good, etc.
•Japanese Industrial Standards Committee (JISC or JIS) - A Japanese agency that establishes and maintains standards for equipment and components.
•Jewel Case - The hard plastic case that contains a compact disc.
•Joule - A unit of energy equal to one watt per second.

K

•Kilo (k) - A prefix meaning thousand.
•Kilohertz (kHz) - 1 kHz equals one thousand hertz or 1,000 times per second.
•Kirchoff’s Current Law - A law stating that the total current entering a point or junction in a circuit must equal the sum of the current leaving that point or junction.

L

•L length of wire immersed in magnetic field, in meters
•Laser Diode - A semiconductor device which emits a laser beam.
•Lces The electrical inductive equivalent of Cms, in henries.
•LCD - Liquid Crystal Display.
•LED - Light Emitting Diode.
•Line Level - The standard preamplifier output level of a signal from an audio source other than a turntable. Usually between 100mV and 1V, but may be as high as 5V or more from some preamplifiers.
•Linearity Error - The deviation in response from an expected or theoretical straight line value for instruments and transducers (speakers).
•Liquid Crystal Display (LCD) - A type of digital display made of a material that changes reflectance or transmittance when an electrical field is applied to it.
•Load - The electrical demand of a process, expressed in current (amps), power (watts), or resistance (ohms).
•Local / Distance Switch - Changes the sensitivity of the tuner. When switched to local (LO), the stronger local stations are received with a higher image rejection. When switched to distance (DX), the weaker, distant stations are received but with less image rejection.
•Loudness Control - Intended to boost low and high frequencies at lower volume levels. These circuits help match the human hearing characteristics at low and high frequencies. Well designed circuits are designed to gradually minimize frequency corrections as the volume is increased.
•Loudspeaker - - An electro acoustic transducer which converts electrical audio signals at its input to audible waves at it's output. May also refer to a given driver of a multiple speaker element systems, but not to the whole speaker system as might a speaker.
•Loudspeaker Compliance - The acoustical and mechanical equivalent of capacitance. Determines how easily a speaker cone/ voice coil assembly will move when an electrical signal is applied to it.
•Low Frequency Driver - A loudspeaker specifically designed to reproduce long, low-frequency wave lengths. The driver typically has a large cone, magnet structure, and voice coil. Woofer.
•Low Pass Filter - A network of elements used to attenuate all frequencies above a predetermined frequency. Frequencies below the cutoff point pass without any effect. •Lows - Term which refers to a set of speaker components used to reproduce frequencies below 500 Hz as in a set of woofers. May also refer to the low frequency drivers of a set of separates. Not treble.

M

•Magnetic Flux - The magnetic lines of force produced in the area around an electric current or magnet.
•Magnetic Structure - The part of loudspeaker comprising the magnet, pole piece, back plate and top plate.
•Maximum Power Rating – A value which means almost nothing, but is used nonetheless by manufacturers to entice the unsuspecting into purchasing their product solely based on big numbers. Technically, it is the maximum wattage that an audio component can deliver/handle as a brief burst during a musical peak. The reliable rating would be the ‘RMS’ rating.
•MECP - Mobile Electronics Certification Program.
•Memory - The word most commonly used to refer to a system's ability to retain specific information.
•Memo List - A Custom File feature that allows the user to toggle through the disc or station titles currently loaded without interrupting playback of the existing disc or station.
•Metal Tape EQ - An equalization circuit that compensates for the unique frequency response characteristics of metal tape.
•Mega (M) - A prefix that means 106 (one million in the US). 1 MHz equals 1,000,000 Hertz.
•Micro (µ) - A prefix that means 1/ 106 (one millionth in the US). 1 µV equals 1/1,000,000 of a volt.
•Midrange Driver - A loudspeaker specifically designed to reproduce the frequencies in the middle of the audible bandwidth. Usually between three and eight inches in diameter. Commonly referred to as the low frequency driver in a set of separates.
•Milli (m) - A prefix that means 1/ 103 (one thousandth). 1 mA equals 1/1,000 of an amp.
•Ms - The total moving mass of the loudspeaker cone.
•Mmd - Diaphram mass, in grams
•Mms - The moving mass of a driver assembly.
•Monaural (mono) - A sound recorded or reproduced in only one channel.
•MOSFET - Metal Oxide Semiconductor Field Effect Transistor. Typically used in high power output amplifiers.
•Mute - Silent, attenuate.
•Multi meter - A common term used to describe a VOM. A multi meter usually has the ability to measure volts, ohms, and amperes or Milli amperes.



N

•Noise - Unwanted sound of no specific frequency or amplitude. Random sound of many frequencies not harmonically related (buzzing, hiss, pops, static, whine, etc.).
•n0 - The reference efficiency of the system (eta sub 0) dimensionless, usually expressed as %,
•Negative LCD - A liquid crystal display employing a dark backfield with lit elements. This results in a primarily dark display, which improves cosmetic integration with a dark colored headunit.
•Negative lead - The lead or line connected to the negative terminal of a current, voltage, or power source.
•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.
•NTSC - National Television System Committee. Refers to the standards used for video broadcast and playback signal parameters.
O

•Octave - The interval of eight diatonic degrees between two musical tones. The doubling or halving of frequencies.1000Hz is an octave higher than 500Hz.
•Ohm - The unit of electric resistance and impedance. One ohm is the resistance value through which one volt will maintain a current of one ampere.
•Ohm's Law - Current in a circuit is directly proportional to the voltage, and inversely proportional to resistance. It also includes the relationships of watts to amps, volts and ohms.
•Over sampling - Doubling or quadrupling (or by even a higher factor of 2 squared) the sampling frequency during the digital to analog process to obtain a high frequency for digital filtering.
•Output - The high level (speaker) or line level (RCA) signals sent from one system component to another or the high level signal from an amplifier to the system speakers.
•Out of Phase - When the speakers are wired with reverse polarity they are known to be out of phase. Because of the phase difference created in the reproduced sound waves.


P

•p (rho) Density of air at STP 1.18 kg/m^3
•Pa Acoustical power
•Parallel Circuit - A circuit configuration in which the same voltage is applied to all components, with current divided among the components according to their respective resistances or impedances. Example: All positive leads of two or more speakers connected together and all negative leads connected together.
•Parametric - A type of equalizer with adjustable parameters such as center frequency and bandwidth (Q) as well as amplitude.
•Passive Crossover – It uses inductor (coils) and capacitors in a series and/or parallel configuration to direct desired frequencies to their respective drivers. It does not use any active electric circuitry for this purpose.
•Passive Radiator – A device that looks like an ordinary driver, except it has no magnet of voice coil. It is usually a high compliant device with a similar cone material and surround found on regular drivers. The radiator must usually be at least as large as (or larger than) the driver it is aligned with. It is acts just like a port in a ported enclosure system but has an advantage over a regular ported box simply because of the elimination of port noise.
•Pe - Electrical power, P = V^2 / R or P = I^2 * R, where V = voltage, I = current and R = resistance.
•Peak - The maximum amplitude of a voltage or current.
•PEI film - Poly-etherimide. A plastic-based polymer used primarily for tweeters and midrange cones offering high resistance against harsh environmental extremes, superior rigidity, damping and resistance against harsh environmental conditions.
•Phase - The relative position of two sound waves with respect to each other.
•Phase Coherence – The relationship and timing of sound coming from different drivers mounted in different locations in a vehicle or a room.
•Phase Distortion - A type of audible distortion caused by the time delay between various parts of the signal.
•Photo Detector (photo diode) - A semiconductor device which provides variations in current as a function of light intensity.
•Piezo Electric Tweeter - A very efficient, highly directional tweeter which operates without a crossover or magnet. Driver creates sound when a quartz crystal receives electrical energy. A highly capacitive load is common in Piezo Tweeter Arrays.
•Pink Noise - Sound with all frequencies perceptible to the human ear reduced to an equal energy level.
•Pink Noise Generator A device used to generate pink noise that usually includes a calibrated microphone coupled to a Real Time Analyzer. Commonly used tool for audio engineers to compensate for room resonance and reflections within a given listening venue.
•Pit - One of the depressions that represents data in a compact disc. May also be referred to as bumps, this is what the pick up lens sees and interprets.
•Plate Speaker - A speaker that has two drivers mounted side by side on a flat surface.
•PMPO – Peak Music Power, used on gears that need to look more powerful than it is.
•Polarity - The electrical quality of having two opposite poles, one positive and one negative. Polarity determines the direction in which a current tends to flow.


•Pole Mount - A common automotive speaker design with the high frequency driver mounted on a center pole. Newer designs mount the high frequency driver in the same location above the lower frequency driver with a bridge. This prevents problems such as dust and dirt from entering at the base of the pole.
•Ported Enclosure - A type of speaker enclosure that uses a sonic duct or a port to improve the efficiency at low frequencies. It applies the out of phase sound wave from the back of the cone and uses it to reinforce the front wave. .
•Power Handling Capability - The maximum amount of power that can be safely accommodated without damage in a speaker system. This will vary depending on frequency and length of time the signal is applied.
•Pre-amp Fader - A circuit that allows effective level control of two amplifiers, built in and external without loss of power.
•Pre-amplifier (pre-amp) - The circuit which takes a small signal and amplifies it to be fed into the power amplifier for further amplification. Contains controls for volume, regulating tone, and channel balance.

Q

•Q - The relative damping of a loudspeaker
•Qa - The system's Q at Fb, due to absorption losses; dimensionless
•Qec - The system's Q at resonance (Fc), due to electrical losses; dimensionless
•Qes - The driver's Q at resonance (Fs), due to electrical losses; dimensionless
•Ql - The system's Q at Fb, due to leakage losses; dimensionless
•Qmc - The system's Q at resonance (Fc), due to mechanical losses; dimensionless
•Qms - The driver's Q at resonance (Fs), due to mechanical losses; dimensionless
•Qp - The system's Q at Fb, due to port losses (turbulence, viscosity, etc.); dimensionless
•Qtc - The system's Q at resonance (Fc), due to all losses; dimensionless
•Qts - The driver's Q at resonance (Fs), due to all losses; dimensionless
•Quantization - The assigning of values to discrete samples of a continuous signal in the analog to digital conversion process.
R
•R - Ripple, AC noise level from a power supply, riding on a DC voltage rail, units in dB
•Radio - A head unit that combines a tuner, a preamplifier, and a power-amplifier. •Radio Frequency Interference (RFI) - Electromagnetic waves between the frequencies of 10 KHz and 300 GHz that can affect susceptible systems by conduction through sensor (tape head) or power input lines, and by radiation through space.
•Ras Acoustical equivalent of RMS
•RAM - Random Access Memory. A memory device that one can write data to and read data from.
•Relay (SPDT) - (Single Pole Double Throw Relay) an electromagnetic switch, consist of a coil (terminals 85 & 86), 1 common terminal (30), 1 normally closed terminal (87a), and one normally open terminal (87).

•Remote Turn On Lead - The power lead from the head unit which supplies a signal (12V+) to the "remote turn on" lead of the amplifier turning the amplifier on when the head unit is turned on, and allowing the amplifier to be mounted in a location out of reach of the user. This is NOT the amplifier's main source of power. It is generally a very low current power source. (200-300 mA max.)
•Res The electrical resistive equivalent of RMS, in ohms
•Resistance - The opposition to the flow of AC or DC voltage in an electric current. Measured in ohms.
•Resistor - An electrical device that resist the flow of electrical current. The higher the value of resistance (measured in ohms) the lower the current and voltage will be. •Resonance - Pitch. When you tighten a drum, you raise its resonance.
•Resonant Frequency - Frequency at which there is a response peak, due to a specific interaction of inductive and capacitive circuitry in an audio devise or system.
•Revc - DC voice coil resistance, in ohms.
•RF Modulator - A device that converts a signal (typically audio and/or video) into a radio frequency.
•Rg - Amplifier source resistance (includes leads, crossover, etc.), in ohms
•Rms - The driver's mechanical losses, in kg/s
•RMS - Root Mean Square. The RMS voltage of an AC waveform corresponds to the same DC equivalent power source and ability to drive an electrical device. (0.707 of peak voltage is considered the RMS value of an AC waveform)
•Ripple - The maximum deviation from flat response, measured in decibels-it indicates the port's effect on woofer output.
•ROM - Read Only Memory. A memory device that one can only read data from. The data has been pre-programmed.
•Roll off (Cut-Off) – The attenuation that occurs at the lower or upper frequency range of a driver, network or a system. The roll off frequency is usually defined as the frequency where the response is reduced by 3 dB.
S

•Sabine - Unit of measurement for absorption. One Sabine is equal to the absorption of 1 square foot of surface which will absorb all incident energy.
•Santoprene - A speaker surround material constructed of Santoprene (a manufactured rubber), offering improved resistance to stretching and deterioration over time compared to Butyl rubber.
•Sampling - Measuring the analog signal at a fixed rate of speed (sampling frequency).
•Satellite speaker – A small speaker with limited bass response often designed to be used with a sub-woofer and/or mid bass.
•Sd - Effective piston radiating area of driver, in square meters
•Sealed Enclosure - A type of speaker enclosure that does not allow the pressure generated by the back wave of the speaker to leave the enclosure.
•Second-Order - The frequency attenuation that occurs at a rate of 12 dB per octave.
•Selectivity (alternate channel) - Similar to capture ratio, but deals with signals which are broadcast on frequencies very close to the one selected.
•Sensitivity (loudspeaker sensitivity) - The sound pressure level a speaker produces when fed by a given input power, measured at a specific distance on axis directly in front of the speaker. Typically specified in dB of SPL at 1 meter with 1 watt of input signal. (Commonly uses a 2.83 reference voltage at 1,000 Hz.)
•Separates - A speaker system with more than one type of driver. The most common type of separates system is a set containing two high frequency drivers (tweeters), two lower frequency drivers (mids or woofers), and two crossover networks (filters). •Separation - The degree to which left and right channels in a stereo signal can be kept apart.
•Series Circuit - A circuit configuration in which a single current path is arranged among all components. Connecting the positive speaker output of an amplifier channel to the positive terminal of speaker # 1, connecting the negative terminal of # 1 to the positive terminal of speaker # 2, and the negative terminal of # 2 to the negative output of the same amplifier channel is a series connection.
•Shield - A metallic foil or braided wire layer surrounding conductors which is designed to prevent electrostatic or electromagnetic interference from external sources.
•Signal - Any electrical transmittance that conveys data.
•Signal-to-Noise Ratio (S/N) - The ratio of the desired signal level to the level of unwanted noise. Measured in decibels.
•Sine Wave – The wave form of a pure alternating current or voltage. It deviates about a zero point to a positive and a negative value. Audio signals are sine waves or a combination of sine waves.
•Slope - The rate of boost or attenuation expressed in decibels of change per octave.
•Slew Rate - This term is used to describe how quickly the output of an amplifier can track its input. It is measured in Volts per millisecond. The higher the values better the amp.
•Sound - A wave propagated in air producing an auditory sensation in the ear by the change of pressure at the ear.
•Sound Field - The total acoustical characteristics of a space, such as ambience [number, timing, and relative level of reflections (ratio of direct to reflected sound).
•Sound Pressure Level (SPL) - An acoustic measurement of sound energy, typically expressed in dB SPL.
•SPLo - Sound Pressure Level, usually measured at 1 watt, at 1 meter in front of the loudspeaker
•Sound Stage - The area that appears to be occupied by sonic images. As with a real stage, a sound stage should have depth, height, and width. There is radiated acoustical energy in all axis, vertical, horizontal and all its vectors.
•Speaker - A transducer which converts electrical energy into acoustical energy (sound). •Spider – The flexible material that supports the former, voice coil and the inside portion of the cone within the speaker frame.
•Standing Waves - Created when two waves in opposite directions interfere. When a reflected wave reinforces a reflection of the original waveform, the sound waves reinforce themselves, increasing in altitude.
•Stereophonic (stereo) - Consisting of two or more audio channels in an audio system during recording and playback to give a more natural distribution of sound.
•Sub Harmonic - The result of the division of the fundamental frequency by the desired number harmonic. The sub harmonic of 1000 Hz is 500 Hz.
•Sub code - Data, other than music, which is stored on a CD, MD, or other digital format. Used to indicate track number, index number, use of emphasis, and other information. •Sub-woofer - A loudspeaker made to reproduce the lowest of audio frequencies, approx. 25 Hz to 125 Hz.
•Super tweeter - A high frequency driver designed to reproduce very high frequencies, typically over 10 kHz.
•Surround – The outer suspension of a speaker cone: holds the diaphragm in place but allows the cone to move when activated, usually made of foam or rubber.

T

•TFT - Thin Film Transistor, Active Matrix Display a specific type of LCD display in which one to four transistors control each pixel. This technique offers the best resolution of all LCD, flat panel display types.
•Threshold of Pain (in dB SPL) - The minimum value of sound pressure of a given frequency that will cause pain to a listener 50% of the time. Discomfort begins at 105 dB SPL. Actual pain starts around 120 dB SPL within the frequency range between 200 Hz and 10,000 Hz.
•Three-Way - A type of speaker composed of three ranges of speakers, usually a mid-bass/woofer, mid-range and a tweeter.
•Timbre - The quality of sound related to its harmonic structure. Timbre is what gives a voice or instrument its sonic signature. That’s the reason why a trumpet and saxophone sound different when they play the same note.
•TOC / Table Of Contents - The sub code information which contains track numbers and times.
•Total Harmonic Distortion (THD) - The noise referenced to signal in decibels (dB) as a percentage.
•Tracking Servo - The control circuit used to keep the pick-up over the desired track.
•Transceiver - A combination radio transmitter/receiver usually installed in a single housing and sharing some components.
•Transducer - A device used to convert energy from one form to another. Acoustical to electrical (microphone), electrical to acoustical (speaker), and electrical to mechanical (Aura Bass Shaker) are three examples of transducers.
•Transient Response – The ability of a speaker to respond to any sudden change in the signal without blurring the sound. A speaker that can react quickly to rapid change in signal has “good transient response”
•Transistor - A three terminal device used for amplification and switching.
•Transmission line enclosure - An enclosure design in which the driver is at one end of the enclosure, with an internal path which consists of a series of bends or curves that lead to a port at the other end of the enclosure.
•Treble – The upper end of the audio spectrum reproduced by tweeters, usually 3 kHz and up.
•Tuner - A component (or section of one) that receives radio signals and selects one broadcast from many.
•Tweeter - A high frequency driver specifically designed to reproduce only the high frequencies (treble) of the audible spectrum.

U

•Under lap - The crossover point being more than 3 dB below the un-attenuated level.


•Unloading – The tendency of an enclosure to produce no spring or pressure on the woofer. Unloading produces an uncontrollable over-excursion of the woofer cone (vibrates uncontrollably). The speaker will exhibit low power handling at lower frequencies.

V

•Variable HP/LP Filter - Crossover components which offer adjustable cut-off frequencies, and levels.
•Vas - "Equivalent volume of compliance", this is a volume of air whose compliance is the same as a driver's acoustical compliance Cms (q.v.), in cubic meters
•Vd - Maximum linear volume of displacement of the driver (product of Sd times X-max), in cubic meters.
•Vented Enclosure - same as ported enclosure.
•Voice Coil - Coil of wire wrapped around a tube (former) and attached to the speaker cone or driver diaphragm. Becomes an electromagnet when an audio signal is applied and interacts with a permanent magnet which causes the cone or diaphragm to vibrate.
•Volt - The unit of measure for electrical potential.
•Voltage - he difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit.
•Voltage Drop - The amount of energy consumed when a device has resistance in its circuit. The voltage (E) set up across a resistance (R) carrying a current (I). E=IR.
•Volume - The amount of space occupied in three dimensions (it's cubic space)-in the case of enclosures, the space inside. It can also refer to the loudness of sound .

W

•Wave - A single oscillation in matter (i.e., a sound wave). Waves move outward from a point of disturbance, propagate through a medium, and grow weaker as they travel farther. Wave motion is associated with mechanical vibration, sound, heat, light, etc.
•Waveform - The shape of a wave.
•Wave length – The length of a sound wave in air. It can be found by dividing the speed of sound in air by the frequency of sound.
•Watt (wattage) - A measurement of real power. The product of voltage and current in a resistive circuit.
•White Noise - Noise in which a constant energy level per unit (1 Hz) is maintained in all frequencies.
•Woofer - A loudspeaker made to reproduce the lower range of the audio spectrum (bass), in a 2-way or more complex speaker system.
•Wow and Flutter - Usually refers to the inconsistencies in tape speed which cause pitch variations and quivering sounds. Wow is slow-speed variations, and flutter is fast-speed variations. Expressed as a percentage, with lower numbers being better.
X

•XM Radio - XM Radio broadcasts 100 channels of totally new music, news, sports and children's programming direct to cars and homes via satellite an extensive repeater network, which supplements the satellite signal to ensure seamless transmission. The channels originate from XM's broadcast center, the world's largest all-digital studio complex in Washington, DC, and uplink to two Boeing 702 satellites. These satellites transmit the signal across the entire continental United States. Each satellite provides 18kw of total power making them the two most powerful commercial satellites ever built, providing coast-to-coast coverage. Not available outside the Continent of North America.
•X-max - The maximum linear cone excursion of a driver.
Y

•Y-splitter – A wire split accessory which is used to split a single wire end into 2 connections.

Z

•Z - Z is also known as nominal Impedance.
•Zero Bit Detection - A circuit in a D/A converter that monitors the digital audio bit stream. Upon encountering all bits low, or zero bits, the output of the D/A is disconnected from the preamp. This improves the signal-to-noise ratio specification
•Zero Output - The absence of output signal or output power.
•Zobel Network - A filter used to stabilize speaker impedance at a crossover frequency where impedance has risen to twice the nominal impedance. It can also be used to attenuate speaker output levels without changing impedance loads to an amplifier.
•Zone - A specific area of a security system's coverage. A specific trigger input of an alarm.
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