Audio Glossary

[Squeak]

2 Way Speakers - A 2-way speaker consists of a tweeter (reproducing high frequencies) mounted in front of a woofer (reproducing low frequencies).

3 Way Speakers - 3-way speakers are the same as 2 way speakers but they add another driver, which usually handles the midranges.

4 Way Speakers - 4-way speakers are the same as 3 way speakers but again, they add another dimension by adding a "super-tweeter" for extended high frequency reproduction.

Accessory (Position) - Refers to the position of the key in the ignition switch; A wire showing 12 Volts (+) when in this position.

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.

Active Crossover - A crossover that takes head unit preouts, then devides them into individual bands for sending onto an amplifier, have variable points at which points the sound is split.

Alternating Current (AC) - An electric current that reverses direction at regular intervals. Measured in Volts AC at Hertz, example (For the Uk): 230 volts AC 50 Hz.

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 whining that is heard 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 (ground loop).

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.

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 (Power) - An amplifier designed for driving loudspeakers and having a higher power output than a line amplifier or preamplifier.

Automatic Volume Control - A useful feature that is found on high end head-units. Some have a microphone that 'listens' to the background noise and some are connected to the car's speedo. This feature prevents the music from becoming inaudible against rising background noise as you speed up.

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.

Bandpass - A two-part filter that cuts both high and low frequencies allowing the band of frequencies between these two points to pass.

Bass - The low audio frequency range typically below 500 Hz (hertz).

Bass Reflex - A vented enclosure that allows control of rear radiated sound waves. Sometimes also known as ported. The hole is usually in the form of a piece of tubing sunk into a wooden box, and has dimensions calculated to give you the deep stuff from the back of the speaker, as well as the front, without canceling itself out - in fact, offering up to twice as much bass as without.

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.

Capacitor - An electrical circuit element used to store charge temporarily, consisting in general of two metallic plates separated by a dielectric.

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.

Chassis - The metal frame of the vehicle.

Circuit Breaker - A device that protects electric circuits by interrupting power in a circuit when an overload occurs. Unlike a fuse a circuit breaker is resetable. Rated in amperes (amps).

Closed Circuit - A continuous unbroken circuit in which current can flow without interruption.

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.

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.

Component Speakers - Component speakers are sold as a set that usually includes four individual speakers (two woofers and two tweeters) with crossovers; all as separate components which can be mounted creatively to achieve the most accurate sound possible. Component speakers cost a bit more than full-range speakers and they're a little more work to install because you'll need to do more than simply replace the factory speakers. The upside is that component speakers provide greater musical detail and clarity compared to most full range speakers.

Crossover - Can be confusing. There are two types of crossover, active crossovers and passive crossovers. Both separate the bass frequencies from the mid and treble frequencies and send the right signals to the right speaker.

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).

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

DC/DC Converter - A group of components within an amplifier that converts battery voltage (DC) into AC so that it can be increased by the switching devices and transformer and converted back to DC (rectified) to provide higher voltage to drive the amplification stage.

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.

Dielectric - An insulating material with low electrical conductivity as used in capacitors.

Digital Output - An output where the signal is in digital form to allow external processing before being converted to an analog signal.

Diode - An electrical circuit element that allows current to flow in one direction.

Direct Current (DC) - An electrical current that flows in one direction.

Directional / Directionality - The angle at which a speaker disperses sound. Higher frequencies are narrower than lower frequencies. Tweeters are more directional than woofers.

Dispersion - Distribution of sound 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.

Double DIN - Twice the height of the standard DIN dimensions; width is standard DIN width.

Driver - Synonymous with loudspeaker. The term also refers to a loudspeaker being coupled to a horn for acoustic coupling and controlled dispersion of sound.

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

Enclosure - A box housing a speaker to separate the front sound waves from the rear sound waves.

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.

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.

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

Filter - An active or passive circuit or device designed to block a certain frequency or range of frequencies.

Floating Ground - Non-common grounding point.

Free Air Response - The frequency at which a speaker will naturally resonate.

Frequency - The number of wavelengths which pass a specific point in a specific time period, measured in Hertz (Hz). Cycles per second.

Frequency Response - The lowest and highest parts of the frequency spectrum that can be reproduced by an audio component within specific limits and tolerances.

Full Range Speakers - Full-range speakers are relatively easy to install, because they are designed to drop into the factory speaker openings.

Fuse - A device that protects electric circuits by interrupting power in a circuit when an overload occurs. Rated in amperes (amps).

Fusible Link - Designed to perform the same task as a fuse, but the resembles a wire. Fusible links are commonly used in ignition switches and other high current circuits.

Gain - The amount of amplification used in an electrical circuit - Not Volume control.

Gauge (wire) - The diameter of a wire. The higher the number, the thinner the wire.

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 paths for electricity are created in a ground line, or when one or more paths are created in a shield or an audio cable. 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.

Hertz (Hz) - The unit of measurement for frequency. 1 Hz is equal to 1 cycle per second.

Head-Unit - The technical name given to the car radio unit. In Europe, we use the standard size of car stereo unit known as 'DIN'. i.e. CD Player, DVD Player, Cassette Player etc.

High Level Input - An input configured to accept speaker level signals.

High Pass Filter - A network of elements used to attenuate all frequencies below a predetermined frequency. Frequencies above the cut off point pass without any effect.

Impedance - The opposition to the flow of alternating current (AC) in a circuit. Measured in ohms.

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.

ISO-DIN Mounting - Refers to a mounting system in which the headunit is mounted behind the dash panel with side brackets, employing factory installed trim panels.

Line Driver - Takes a small head unit preout (eg 2 Volt) and amplifies it to a much higher voltage(around 8 to 10 Volts).

Loudness Control - Intended to boost low frequencies at lower volume levels and should not be used at high volume listening levels.

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 system and not to the whole speaker system as might a speaker.

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 cut off point pass without any effect (usually subwoofers).

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.

Mono - A sound recorded or reproduced in only one channel.

Monoblock - An amplifier that only has only one channel output.

MP3 - MP3 is just a method of compressing files. Its name is an abbreviation for the much more unwieldy MPEG (Moving Picture Experts Group) 1 Layer 3. All you really need to know, though, is that MP3 files are about one-tenth the size of uncompressed audio files.

Noise - The unwanted sound of no specific frequency or amplitude or random sound of many frequencies not harmonically related (buzzing, hiss, pops, static, whines, etc.).

Nominal Impedance - This is the speaker's average resistance to the flow of current through the circuit going from the amplifier into the speaker and back to the amplifier.

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.

Oversampling - A digital electronics method for the CD machines to be absolutely certain that the information they are playing will play as music.

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.

Phase - The relative position of two sound waves with respect to each other.

Phase Shift - Frequency interaction in the crossover region of passive crossovers which can cause some frequencies to be delayed with respect to other frequencies.

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.

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-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.

Passive Crossover - Comes usually with components and controls which frequency goes to which speaker.

RCA - Leads which run from head unit preout to amplifiers, active crossovers or surround sound decoders, carry audio signals. Sometimes referred to as phono leads.

Remote Turn On Lead - The 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.

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 will be.

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

RMS - RMS Means 'Root Mean Square', which refers to the output power of an amplifier in watts. Although it should really be qualified by stating the RMS value in relation to the music, i.e. '20 Hz to 20kHz, 4 Ohms', this is the single most reliable rule to use when comparing the wattage of amps.

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.

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 - An expression to give you some idea as to how 'hi' your 'fi' really is. A reading of 90dB is a lot of signal for a little noise (hiss) and will always indicate a good piece of kit. Higher than this and your talking special. Also applies to any audio unit of any kind.

Sound - A wave propagated in air producing an auditory sensation in the ear by the change of pressure at the ear.

Speaker - A transducer which converts electrical energy into acoustical energy (sound).

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-woofer - A loudspeaker made to reproduce the lowest of audio frequencies, approx. 25 Hz to 125 Hz.

Suppressor - A filtering device used to cut out 'noise' from a system.

Switch - A switch is any form of mechanical, electronic, electromechanical, magnetic, or mercury device that either opens or closes a circuit.

Toroidal Coil - An inductor or transformer whose core consists of a concentrically wound ribbon of magnetic material. Also used to filter noise on a DC supply line.

Triaxial Speakers - Triaxial is a design where there are there are two smaller speakers mounted in front of the bigger speaker.

Tweeter - A high frequency driver specifically designed to reproduce only the high frequencies (treble) of the audible spectrum.

Voice Coil - Coil of wire wrapped around a tube 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 - The 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 (V) set up across a resistance (R) carrying a current (I); V=IR.

Watt - A measurement of real power. The product of voltage and current in a resistive circuit.

Wavelength - The length of distance a single cycle or complete sound wave travels.

Woofer - A loudspeaker made to reproduce the lower range of the audio spectrum (bass), in a 2-way or more complex speaker system.

Xmax - This represents the longest linear cone movement in one direction.

Zmax - This parameter represents the speaker’s impedance at resonance.