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1-W SPL - The reference sensitivity of a driver with a 1 watt signal and measured at 1 meter as a sound pressure level (dBSPL). 

2.8-V SPL - The reference sensitivity of a driver with a2.83 volt signal and measured at 1 meter as a sound pressure level (dBSPL). 

 

A 

Accessory (position) - One position of an ignition switch prior to the start (or crank) position; A wire showing 12 Volts (+) when the vehicle is both running and not running. 

Acoustic Absorption - The sound deadening properties of a substance, measured in Sabine units. One Sabine is equal to the absorption of 1 square foot of surface which will absorb all acoustic energy. 

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. 

Aligned - The drivers in a multi-loudspeaker system are "aligned" when the sound produced by each driver in the system arrives at a specific location in at the same time. 

Alternating Current (AC) - An electric current that reverses direction at regular intervals. Measured in Volts AC at a specific frequency (Hertz) Example: 110 volts AC - 60 Hz. 

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 electrical device that measures the magnitude of an electric current in amperes. 

Ampere (amp) - 1.) A unit of measurement that defines the rate of flow of electricity (current) in a circuit. 2.) The amount of current that flows when a pressure of 1 volt is applied across a resistance of 1 ohm. 

Amplification - The process of increasing a signal in level, amplitude or magnitude. 

Amplifier - 1.) A device which increases the level of a signal by increasing the current and/or voltage. 2.) A device which is used to isolate or control a signal or decrease a level as in the case of 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 its amplitude in accordance with an input signal. 

Amplitude Response - A comparison of the magnitudes of an input and output signal versus frequency. This is commonly referred to as "frequency response". The output signal is usually measured as a pressure level. 

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. 

Analog to Digital Converter (AC-DC) - A circuit that converts an analog signal into a digital signal. With a continuous input signal this device will check the signal several times per second (referred to as sampling), then assign values to the samples and represent them as a binary number (referred to as quantization and encoding). 

Analogous - Alike in certain ways. Similar in function but not in origin or structure. 

APC - An all-pass crossover network with a flat amplitude response. 

Attenuator - A device used to increase or decrease the strength of a signal. 

Automatic Gain Control (AGC) - A circuit that continuously adjust the recording amplifier gain to maintain a relatively constant recording level. 

 

B

Balance - The relative volume level between two channels, usually the left and right channels of a stereo signal. May also refer to the relative volume between front and rear channels of an audio system (normally referred to as fading). To make the same or equal. 

Bandpass Filter - A two-part filter that attenuates both high and low frequencies at specific points, allowing the specific frequencies between these two points to pass. 

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 decreased by three decibels. 

Basket - The frame of a loudspeaker that supports all of its components. 

Bass - The low audio frequency range typically below 350Hz (Hertz). 

Bass Reflex - A woofer enclosure that has a vent/port, allowing the rear wave of the woofer to combine with the front wave. Referred to as a vented and/or ported enclosure. 

Bessel - A filter type with a Q = 0.58 that produces a nearly flat amplitude response and group delay with a Ð5 to-7 _ dB crossover point. 

Bi-Amplification / (Bi-Amp) - 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 a crossover and divided into two separated signals. These signals are sent to the loudspeakers.(bass to woofers, midrange and treble to mids and tweeters). A tri-amplification is the use of three amplifiers in the same manner with the audio signal divided into three separate bands of frequency by the crossover and so on. 

Binary Digit (bit) - The smallest unit of data in a digital signal represented by either a one or zero. 

BL - The motor strength of a driver. 

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. 

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. This provides the 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. The B & S Gauge is identical to the American Wire Gauge (AWG). 

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. 

Butterworth - A CPC filter type with a Q = 0.707 producing a flat power response and a -3 dB crossover point. 

Byte - Eight bits. It takes one byte to represent one letter of the alphabet. 

 

C 

Capacitance - 1.) The ability of a conductor or dielectric to store electric charge. 2.) The property of a device to oppose changes in voltage due to energy stored in its electrostatic field. Expressed in Farads (F) 

Capacitor - 1.) A device whose impedance increases with decreasing frequency. 2.) An electrical circuit element used to store charge temporarily, consisting in general of two metallic plates separated by a dielectric. (polarized) 3.) A crossover component used to filter out lower frequencies and allow higher frequencies to pass. (non-polarized) 

Capture Ratio - Expressed in decibels, with the smaller the number the better. The ratio of captured signals of different strength on the same frequency. 

Chebychev - A filter type with a Q = 1.0 that produces a 0 dB crossover point and approximately ±2 dB of ripple in the amplitude response. 

Circuit - 1.) Any closed path followed by electrical current. 2.) A configuration of electrically or electro-magnetically 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 is resettable. Rated in amperes (amps). 

Clipping - Audible distortion that occurs when continuous power-to-peak power capabilities (headroom) are exceeded. 

Cms Ð The mechanical compliance of a loudspeaker. 

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. 

Coincidence - When two identical signals occupy the same point in space and time. They will sum to +6 dB if they have the same polarity. If one has an inverted polarity, they will cancel each other. Two signals which are not coincident will usually sum to +3 dB. 

Coincident - When two drivers are constructed such that their acoustical centers appear to be in the same location in space at their crossover frequencies, they are said to be coincident. 

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 radiating surface of a loudspeaker. 

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. 

Coverage - The area to which a driver delivers a uniform sound. Referred to as "the coverage area". Usually described with angles, i.e. a driver has a 40° vertical coverage. Coverage in most drivers decreases as the frequency increases. 

CPC - A constant power crossover network with a flat power response. 

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 - An electric circuit that divides the audio spectrum into two or more frequency bands. The two types are active and passive. 

Crossover Point - The crossover point is the frequency and level where the signals from the drivers intersect. Similar to 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 

DCR - the DC resistance of an electric device such as an inductor or capacitor. 

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. 

Deutsche Industrie Normen (DIN) - German (European) industrial standards. DIN size refers to the stereo size that fits most European automobiles. 

DF - The system damping factor. This can be the damping factor of an enclosure or the damping factor of an amplifier output. 

Dia. - The piston diameter of a driver or passive radiator. Dielectric - An insulating material with low electrical conductivity. 

Diffraction - The bending of sound waves as they pass near an edge or corner of a solid object. 

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) - 1.) The flow of electrons in one direction depending on the polarity of the energy source. 2.) 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 - 1.) Sound that is modified or changed in some way. Measured as a percentage of the whole signal. 2.) Any change in the waveform or harmonic content of an original signal as it passes through a device. When a signal flowing thru a circuit is compared at two different points, any change except for magnitude is distortion. 

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

Dynamic Range - 1.) 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 (dB), the higher the number the better. 2.) The difference between the maximum signal level and the noise floor of an electronic component. 

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. 

 

E 

EBP - The efficiency bandwidth product (Fs/Qes) 

Effect Loop - A signal path which allows an audio processor to be switched in and out of the signal path such as an equalizer. 

Effective Voltage - A value assigned to an AC sine wave voltage that has the same effect as an equal value of DC voltage. Also known as RMS or Root Mean Square. 

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. With amplifiers, this refers to the combined efficiency of the power supply and audio stages stated as a ratio of total energy input to total energy output. This is commonly misrepresented by the power supply efficiency only. 

Electron Current Flow - Current flow that is assumed to be in the direction of electron movement from a negative (-) potential to a positive (+) potential 

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. 

Electro-magnetic Interference (EMI) - The interference caused by an electro-magnetic field created by the flow of current. 

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. 

ESR - The equivalent series resistance of an electric device such as an inductor or capacitor. 

Evenhung - Describes when a voice coil is equal to the height of the magnet gap. 

 

F 

F3 - The half-power (-3dB) frequency of a system. 

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. 

Fb - the system resonant frequency of an enclosure. It is also called the "tuning frequencyÕ of an enclosure with a vent. 

FFT - Fast Fourier Transform. A mathematical method of converting a continuous-time signal into a discrete-time signal so that it can be analyzed digitally. 

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

Fill - The acoustical absorption or damping added inside an enclosure to suppress unwanted resonanceÕs. 

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 range (due to ear canal resonance). 

Floating Ground - Non-common grounding point. 

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. 

Free Air Resonance (Fs) - The frequency at which a loudspeaker vibrates most easily. 

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

Frequency Modulation (FM) - The encoding of a carrier wave by variation of its frequency in accordance with an input signal. 

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. 

Frequency Dividing Network - See crossover network. 

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 - The free-air resonant frequency of a driver or passive radiator. 

Fundamental Frequency - The principal component of a complex waveform having the lowest frequency. 

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 circuit. 

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

Gaussian - A filter type that uses an asymmetrical filter topology and a Ð6 dB crossover point. 

Giga - Prefix meaning 109 or 1,000,000,000 (1 billion in the US) 

Graphic (equalizer) - Refers to a type of equalizer with sliding controls that create a pattern representing a graph of frequency response changes. 

Ground - 1.) The term given to the return path for current flow with a relative potential of zero. 2.) An electrical line with the same electrical potential as the chassis of the vehicle, most commonly negative 12 volts DC. 

Ground Loop - 1.) A term used when two or more devices have grounds that are not exactly at the same relative electrical potential. When this occurs, there is a current flow established between the two ground potentials due to this difference. The current appears as signal on audio cables which can be amplified by an audio system. 2.) 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. 

Ground Potential - 1.) The electrical potential of a vehicleÕs chassis. 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 - The delay of an output signal compared to the input signal. Derived from the slope of the phase response and is expressed in milliseconds (msec). 

 

H 

Henry/Henries (Hy) - The measurement for inductance. Coils (inductors, low pass filters) are measured in millihenries as in 6.4 mHy (6.4 millihenries). 

Hertz (Hz) - The unit of measurement for frequency. 1Hz 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 Pass Filter - 1.) A network of elements used to attenuate all frequencies below a predetermined frequency. Frequencies above the cutoff point pass without any effect. 2.) A filter used to pass frequencies higher than a predetermined point. Frequencies lower than the F3, or crossover point, are attenuated at a rate determined by the design of the filter. 

High-Q Filters - Hi-Q filters are used for adjusting narrow frequency bands in an equalizer. Filter "Q" or Quality Factor is a measure of the "narrowness" of the filter response. Hi-Q filters are used for avoiding adjacent band overlap in an equalization circuit. 

 

I 

IASCA - International Auto Sound Challenge Association 

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 (ghost, 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. 

Impedance - 1.) The opposition to the flow of alternating current (AC) in a circuit. Measured in ohms. 2.) The combined effect of a speaker's resistance, inductance, and capacitance that opposes the current fed to it. It is measured in ohms and varies with the frequency of the signal. This opposition is from all sources, both resistive and reactive. 

Inductance - 1.) The ability to induce an electrical current. Measured in Henrys. 2.) The property of an electric circuit that resists a change in current flow. 

Inductor - 1.) A device whose impedance increases with increasing frequency. Also referred to as a coil. 2.) A device designed to create an electromotive force (emf) because its primary characteristic is inductance. Used in passive crossovers as a low pass filter device. 

Infinite Baffle - 1.) An enclosure that is larger than the VAS of a driver. 2.) Any baffle board where there is no path for the energy from the rear of the woofer to meet the energy from the front of the woofer. 

Input Sensitivity Control - Adjusts the amount of input signal being fed to the amplifier stage. 

Insertion Loss - The attenuation in dB of a signal through an inductor . Inductors exhibit varying degrees of efficiency, dependent primarily on their DCR and this is what causes insertion loss. 

Insulation - A material that electrically isolates a conductor or thermally isolates an object from its surroundings. 

Insulator - A material that offers a high resistance to electrical current flow. 

Intermodulation Distortion (in loudspeakers) - 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.

Isobaric - Constant pressure. Isobaric mounting arrangements cause the pressure in the chamber between the drivers to remain constant because both drivers are fed the same signal and their pistons move in the same direction simultaneously. 

 

J

Jacket - The outer covering on a cable or wire that may provide electrical insulation and/or resistance to abrasion, chemicals, and moisture. 

Japanese Industrial Standards Committee (JISC or JIS) - A Japanese agency that establishes and maintains standards for equipment and components. 

 

K 

Kilo (k) - A prefix meaning thousand. 

Kilohertz (kHz) - 1 kHz equals one thousand hertz or 1,000 cycles per second. Formerly referred to as kilocycles (kc). 

 

L 

Laser Diode - A semiconductor device which emits a laser beam. 

Le - the inductance that a driver "appears" to have because of the inductive reactance of its voice coil. 

LED - Light emitting diode. 

Legendre - A filter type that uses an asymmetrical filter topology and a Ð1 dB crossover point. 

Linear-Phase - A filter type that uses an asymmetrical filter topology and a Ð6 dB crossover point. 

Linearity Error - The deviation in response from an expected or theoretical straight line value for instruments and transducers (speakers). 

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 10V or more from some preamplifiers or line drivers. 

Linkwitz-Riley - An APC filter type with a Q = 0.49 that produces a Ð6 dB crossover point and a flat amplitude response. Referred to as a "squared Butterworth" filter. 

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). 

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 alternating current (AC) audio signals at its input to audible sound 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 does the term 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. Typically referred to as a woofer or subwoofer. 

Low Pass Filter - 1.) A grouping of electrical components used to attenuate all frequencies above a predetermined frequency. Frequencies below the cutoff point pass without any effect. 2.) A filter used to pass frequencies lower than a predetermined point. Frequencies higher than the F3, or crossover point, are attenuated at a rate determined by the design of the filter. 

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. 

 

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. 

Maximally Flat - An amplitude response curve with the least possible ripple in the passband. 

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 or a speaker. 

Milli (m) - A prefix that means 1/ 103 (one thousandth). 1 mA equals 1/1,000 of an amp. 

Minimum Phase - A system whose phase response is directly related to its amplitude response and that has no more phase shift other than what is required by the slope of its amplitude response curve. 

Misaligned - Speakers are "misaligned" when the sound emanating from each driver in the system arrives at a different time. 

MLS - A pseudo-random maximum length sequence signal used for testing loudspeakers and audio systems. 

Mms - the mechanical mass of a driver diaphragm assembly including the air load. 

Modulation Distortion - the distortion that results from the interaction of overlapping audio signals in the crossover region. 

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. 

 

N

Noise - 1.) Unwanted sound of no specific frequency or amplitude. 2.) Random sound of many frequencies not harmonically related (buzzing, hiss, pops, static, whine, etc.). 

Nonpolarized - A device is nonpolarized if it passes a signal equally well in both directions. Nonpolarized components are necessary for audio circuits because audio signals are AC signals. 

 

O 

Occupational Safety and Health Act (OSHA) - The United States governmental agency that establishes and enforces safety standards in the workplace. 

Octave - 1.) A two-to-one change in frequency Example: 1000Hz is an octave higher than 500Hz. 2.) The interval of eight diatonic degrees between two musical tones. 3.) The doubling or halving of a given frequency. 

Ohm - The unit of measurement of electrical resistance. One ohm is the resistance value through which one volt will maintain a current of one ampere. 

Ohm's Law - 1.) The law that explains the relationship of voltage, current, and resistance in electrical circuits. Current in a circuit is directly proportional to the voltage, and inversely proportional to resistance. For example: V = I x R; I = V / R; R = V / I It also includes the relationships of watts to amps, volts and ohms. 

On-Axis - when a loudspeaker or driver is pointing directly at something it is "on-axis". At a 90° angle to the radiating surfaceÕs general axial plane. 

Open Circuit - A circuit that has a broken path so that no electrical current can flow through it. 

Order - A numerical filter classification that is determined by counting the total number of capacitor and inductor sections in the filter. (Exception: Bandpass filters) The order describes how fast a filter will attenuate a signal in the stopband. 

Overhung - Describes when a voice coil is taller than the height of the magnet gap. 

Oversampling - Doubling or quadrupling (or by even a higher factor of 2 squared) the sampling frequency during the digital to analog process in order to obtain a high enough frequency for digital filtering. 

 

P

Parallel - A method of wiring that connects components side-to-side. 

Parallel Circuit - 1.) A circuit in which the components are connected across each other. 2.) A circuit whose component leads bridge common conductors like a ladder. 3.) 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 of the same speakers connected together. 

Parametric - A type of equalizer with adjustable parameters that include the center frequency, the bandwidth (Q) and the amplitude of the signal. 

Passband - the portion of sound that is passed by a filter. 

Pass-Thru - A "pass-thru" or "all-thru" is a signal that is outputted thru an electrical device without being modified. This output is a connection point where you can daisy-chain audio components without the need for "Y" adapters. The pass-thru signal in a four-channel amplifier is derived by summing the Front And Rear Left inputs to create a LEFT OUTPUT, and summing the Front and Rear Right inputs to create a RIGHT OUTPUT. 

Passive Crossover - A single or group of electronic parts responsible for dividing or blocking a frequency range or ranges. Passive crossovers are used to divide frequencies after the power amplifier and before the loudspeakers in a system. 

Pe - the maximum electrical power that a driver can handle before being damaged. 

Phase - 1.) the change, measured as an angle, that an alternating current undergoes with the passage of time. 2.) The relative position of two sound waves with respect to each other. 

Phase Shift - Any delay in a signal flowing thru a circuit that is compared at two different points is a phase shift . 

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. The driver creates sound when a quartz crystal receives an electrical energy input and converts this to acoustical energy. 

Pink Noise - Sound with all frequencies perceptible to the human ear reduced to equal energy levels. Commonly used to adjust relative energy levels in audio systems. 

Pink Noise Generator - A device used to generate pink noise. 

Piston Band - The frequency band where a driver maintains a constant load versus frequency. 

Pit - One of the depressions that represents data in a compact disc. 

Plate Speaker - A speaker that has two drivers mounted side by side on a flat surface.

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. 

Port - 1.) A tunnel which allows the passage of air in and out of a loudspeaker enclosure. 2.) A specified opening used to "tune" a 3rd order or ported enclosure. Commonly referred to as a "vent". 

Potentiometer - A variable-resistance component used as a control device in an electrical circuit. 

Power - The rate at which work is accomplished. The product of voltage and current. 

Power Handling - 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. CAUTION!: Can be specified by various methods. 

Power Response - The total acoustic power emanated from a loudspeaker or driver. Does not change with direction or distance from the source. 

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. 

Pre-amp Fader - A circuit that allows effective level control of two amplifiers, built in and external without loss of power. 

Push-Pull - When two drivers are mounted in opposite directions and wired with opposite polarity with respect to each other (i.e. out of phase). This configuration results in a reduction in even-order distortion due to driver suspension nonlinearities being cancelled. 

 

Q

Q - The resonance magnification of a system. 

Qa - The Q of an enclosure resulting from all absorption losses. 

Qes - The Q of a driver at Fs considering ONLY its electrical resistance. 

QL - The Q of an enclosure resulting from all leakage losses. 

Qms - The Q of a driver or passive radiator at Fs considering ONLY its mechanical resistance. 

Qts - The total Q of a driver at Fs considering both electrical and mechanical resistance. 

Quantization - The assigning of values to discrete samples of a continuous signal in the analog to digital conversion process. 

 

R

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. 

Re - The DC resistance of a driverÕs voice coil. 

Reactance - An opposition to the flow of electricity because of capacitive and inductive characteristics. Purely resistive characteristics are not included in reactance. 

Relay - (SPDT - Single Pole Double Throw) an electro-magnetic 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 electrical signal usually given as a wire lead from the head unit which supplies a 12V+ source to the "remote turn on" lead of an electrical device, activating the device when the head unit is turned on. This should NOT be used as a deviceÕs main source of power. 

Resistance - The opposition to the flow of electricity without capacitive and inductive characteristics. 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 it allows to pass thru. 

Resonance - 1.) Pitch or tone. 2.) The frequency of peak response of a device that results from the balance of its capacitive and inductive characteristics. 

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. 

RMS - Root Mean Square. (see Effective Voltage) 

Rms - the mechanical resistance of a driver or passive radiator suspension losses. 

RTA - An instrument that continuously measures sound pressure level. 

 

S

Sabine - Unit of measurement for absorption. One Sabine is equal to the absorption of 1 square foot of surface area which will absorb all incident energy. 

Sampling - Measuring the analog signal at a fixed rate of speed (sampling frequency). 

Sd - the piston area of a driver or passive radiator. 

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. Also referred to as an Acoustic Suspension enclosure. 

Semiconductor - A material that has electrical resistance somewhere between a conductor and an insulator. 

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 SPL at 1 meter with 1 watt of input signal. 

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 - A method of wiring that connects components end-to-end. 

Series Circuit - 1.) A circuit configuration in which a single current path is arranged among all components. 2.) An electrical circuit whose components are connected in a string, i.e., end to end like a chain. 

Series-Parallel Circuit - The interconnection of components in series and in parallel to obtain a greater power dissipation than with a single component. 

Shield - A metallic foil or braided wire layer surrounding conductors which is designed to prevent electrostatic or electromagnetic interference from external sources. 

Short Circuit - A circuit that forms a direct path across a voltage source so that a very high and possibly unsafe electrical current flows. 

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. Signal-to-Noise Ratio 10.0 dB 20.0 dB 30.0 dB 40.0 dB 50.0 dB 60.0 dB 70.0 dB 80.0 dB Times Signal is Greater than Noise 3.16 10.00 31.62 100.00 316.20 1,000.00 3,162.00 10,000.00 

Slope - 1.) The rate of boost or attenuation expressed in decibels of change per octave. 2.) The attenuation rate of a filter. Sound - An energy wave propagated in air producing an auditory sensation in the ear by the change of air pressure. 

Soundfield - The total acoustical characteristics of a space; i.e. 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 dBSPL. 

Soundstage - The area that appears to be occupied by sonic images. As with a real stage, a soundstage should have depth, height, and width. 

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

SPL - Sound Pressure Level. Unit: Decibels (dB) 

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 amplitude. 

Stereophonic (stereo) - Consisting of two or more audio channels in an audio system during recording and playback to give a more realistic distribution of sound. 

Stopband - The portion of sound that is attenuated by a filter. 

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. 

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

Supertweeter - A high frequency driver designed to reproduce very high frequencies, typically over 10 kHz. 

 

T

Tera (T) - A prefix meaning 1012 or 1,000,000,000,000 (one trillion in the US). 

Thiele-Small - Driver and passive radiator analysis parameters. 

Three-way - A crossover network that includes a low-pass, a bandpass and a hi-pass filter to divide the signal three ways between a woofer, a midrange and a tweeter. 

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 118 dB SPL. Actual pain starts around 140 dB SPL within the frequency range between 200 Hz and 10,000 Hz. 

Topology - The general layout of a circuit including the location of its associated components. 

Total Harmonic Distortion (THD) - The noise referenced to signal in decibels (dB) as a percentage. Thus: Noise referenced to Signal -10.0 dB -20.0 dB -30.0 dB -40.0 dB -50.0 dB -60.0 dB -70.0 dB -80.0 dB Percent Distortion 31.6% 10.0% 3.16% 1.00% 0.316% 0.100% 0.0316% 0.0100% 

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. 

Transistor - A three terminal device used for amplification and switching. 

Treble - The highest frequencies in the audible spectrum. 

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

Two-way - A crossover network that includes a low-pass and a hi-pass filter to divide the signal two ways between a woofer and a tweeter. 

 

U

Underlap - The crossover point being more than 3 dB below the unattenuated level. 

Underhung - Describes when a voice coil is shorter than the height of the magnet gap.

 

V

Vas - The volume of air having the same compliance as the suspension of a driver or passive radiator. 

Vb - The net internal volume of an enclosure. 

Vd - The piston displacement volume of a driver or passive radiator at Xmax. 

Voice Coil - A wire wrapped around a tube and attached to a speaker cone or driver diaphragm. Becomes an electromagnet when an audio signal is applied and interacts with a permanent magnet which causes the cone body or diaphragm to move. 

Volt - The unit of measure for electrical potential. 

Voltage - 1.) The difference in electrical potential between two points in a circuit. 2.) Electrical force, or pressure, that causes current to flow in a circuit. 

Voltage Drop - The electrical potential (voltage) that exists across two points of an electrical circuit. 

 

W

Watt (wattage) - 1.) The product of voltage and current in a resistive circuit. 2.) The unit of measurement of electrical or acoustical power. 3.) The amount of power converted when 1 ampere of current flows under a pressure of 1 volt. 

White Noise - Noise in which a constant energy level per unit (1 Hz) is maintained in all frequencies. 

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

 

X

Xmax - The maximum linear excursion of a driver. 

Xmech - The maximum mechanical excursion of a driver. 

 

Y 

 

Z 

Z - the nominal electromagnetic impedance of a driver. 

Zobel - A filter used to stabilize speaker impedance at a crossover frequency where impedance has risen to twice the nominal impedance.