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M-

Magnet - A device which has the ability to attract or repel pieces of iron or other magnetic material. Speaker magnets provide a stationary magnetic field so that when the coil produces magnetic energy, it is either repelled or attracted by the stationary magnet.
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Magnetic Flux - The magnetic lines of force produced in the area around an electric current or magnet.
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Magnetic Structure - The part of loudspeaker comprising the magnet, pole piece, back plate and top plate.
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MECP - Mobile Electronics Certification Program.
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Mega (M) - A prefix that means 106 (one million in the US). 1 MHz equals 1,000,000 Hertz.
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Memory - The word most commonly used to refer to a system's ability to retain specific information.
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Micro (? - A prefix that means 1/ 106 (one millionth in the US). 1 猩 equals 1/1,000,000 of a volt.
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Microprocessor - A semiconductor that can be programmed to perform a variety of tasks in many different systems.
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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.
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Milli (m) - A prefix that means 1/ 103 (one thousandth). 1 mA equals 1/1,000 of an amp.
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Mmd - Diaphram mass, in grams
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Mms - The driver's effective mechanical mass (including air load), in kg. "This parameter is the combination of the weight of the cone assembly plus the river radiation mass load? The weight of the cone assembly is easy: it just the sum of the weight of the cone assembly components. The driver radiation mass load is the confusing part. In simple terminology, it is the weight of the air (the amount calculated in Vd) that the cone will have to push."
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Monaural (mono) - A sound recorded or reproduced in only one channel.
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MOSFET - Metal Oxide Semiconductor Field Effect Transistor. A form of field-effect transistor controlled by voltage rather than current, like a bipolar transistor. MOSFETs have a significantly higher switching speed than bipolar transistors. They generate almost no loss (little heat generation), which lends the power supply fast response, excellent linearity, and high efficiency. Typically used in high power output amplifiers.
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Ms - The total moving mass of the loudspeaker cone.
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Multimeter - A common term used to describe a VOM (voltage ohm meter). A multimeter usually has the ability to measure volts, resistance (ohms), and amperes or milliamperes.
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Music - 1. an art of sound in time that expresses ideas and emotions in significant forms through the elements of rhythm, melody, harmony, and color. 2. the tones or sounds employed, occurring in single line (melody) or multiple lines (harmony), and sounded or to be sounded by one or more voices or instruments, or both. 3. musical work or compositions for singing or playing. 4. the written or printed score of a musical composition. 5. such scores collectively 6. any sweet, pleasing, or harmonious sounds or sound: the music of the waves 7. appreciation of or responsiveness to musical sounds or harmonies: Music was in his very soul.
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Mute - Silent, attenuate.

N-


n0 - The reference efficiency of the system (eta sub 0) dimensionless, usually expressed as %
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Nano (n) - A prefix meaning 10-9 or 0.000 000 001
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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.).
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Nominal Impedance - The minimum impedance a loudspeaker presents to an amplifier, directly related to the power the speaker can extract from the amplifier.
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Normally Closed - Refers to the electrical state in which a switch may rest. Its contacts are held together or closed so that current is allowed to flow through its contacts.
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Normally Open - Refers to the electrical state in which a switch may rest. Its contacts are held apart or open so that no current flows through its contacts.
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NTSC - National Television System Committee. Refers to the standards used for video broadcast and playback signal parameters.

O-


Occupational Safety and Health Act (OSHA) - The United States governmental agency that establishes and enforces safety standards in the workplace.
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Octave - 1. The interval of eight diatonic degrees between two musical tones. 2.The doubling or halving of frequencies.1000Hz is an octave higher than 500Hz.
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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.
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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.
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OSHA - Occupational Safety and Health Administration. The government agency which regulates workplace safety and health.
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Oversampling - 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.

P-


p - rho) Density of air at STP 1.18 kg/m^3
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Pa - Acoustical power
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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.
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Parametric - A type of equalizer with adjustable parameters such as center frequency and bandwidth (Q) as well as amplitude.
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Passive Arming - The ability of some security systems to arm without requiring any direct action from the operator of the vehicle.
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Pe - Electrical power
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Peta (P) - A prefix meaning 1015 or 1,000,000,000,000,000
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Phase - The relative position of two sound waves with respect to each other.
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Phase Shift - Frequency interaction in the crossover region of passive crossovers which can cause some frequencies to be delayed with respect to other frequencies.
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Photo Detector (photo diode) - A semiconductor device which provides variations in current as a function of light intensity.
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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.
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Pink Noise - Sound with all frequencies perceptible to the human ear reduced to an equal energy level.
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Pink Noise Generator - A device used to generate pink noise that usually includes a calibrated microphone.
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Pinswitch - A simple spring-loaded mechanical switch used in many different vehicles designed to turn on interior lights when doors are opened. Pinswitches are also used in the installation of most security systems in the hood or trunk/hatch as a means of triggering the system should these points be opened
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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 sees.
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Plate Speaker - A speaker that has two drivers mounted side by side on a flat surface.
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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.
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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.
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Potentiometer - A variable resistor made with either carbon or wire wound material which attenuates a signal.
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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.
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Pre-amp Fader - A circuit that allows effective level control of two amplifiers, built in and external without loss of power.
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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
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Q Parameters - "Qms, Qes, and Qts are measurements related to the control of a transducer's suspension when it reaches the resonant frequency (Fs). The suspension must prevent any lateral motion that might allow the voice coil and pole to touch (this would destroy the loudspeaker). The suspension must also act like a shock absorber. Qms is a measurement of the control coming from the speaker's mechanical suspension system (the surround and spider). View these components like springs. Qes is a measurement of the control coming from the speaker's electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock. Qts is called the 'Total Q' of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same.

As a general guideline, Qts of 0.4 or below indicates a transducer well suited to a vented enclosure. Qts between 0.4 and 0.7 indicates suitability for a sealed enclosure. Qts of 0.7 or above indicates suitability for free-air or infinite baffle applications. However, there are exceptions! The Eminence Kilomax 18 has a Qts of 0.56. This suggests a sealed enclosure, but in reality it works extremely well in a ported enclosure. Please consider all the parameters when selecting loudspeakers. If you are in any doubt, contact your Eminence representative for technical assistance."
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Qa - The system's Q at Fb, due to absorption losses; dimensionless
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Qec - The system's Q at resonance (Fc), due to electrical losses; dimensionless
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Qes - The driver's Q at resonance (Fs), due to electrical losses; dimensionless. "A measurement of the control coming from the speaker's electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock."
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Ql - The system's Q at Fb, due to leakage losses; dimensionless
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Qmc - The system's Q at resonance (Fc), due to mechanical losses; dimensionless
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Qms - The driver's Q at resonance (Fs), due to mechanical losses; dimensionless. "A measurement of the control coming from the speaker's mechanical suspension system (the surround and spider). View these components like springs."
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Qp - The system's Q at Fb, due to port losses (turbulence, viscousity, etc.); dimensionless
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Qtc - The measurement of a speaker and enclosure working together as one. The system's Q at resonance (Fc), due to all losses; dimensionless
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Qts - The measurement of the speaker as a motor taking into consideration all mechanical and electrical losses. The driver's Q at resonance (Fs), due to all losses; dimensionless. "The 'Total Q' of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same."
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Quantization - The assigning of values to discrete samples of a continuous signal in the analog to digital conversion process.

R-


R - Ripple, in dB
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Radio - A head unit that combines a tuner, a preamplifier, and a power-amplifier.
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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.
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RAM - Random Access Memory. A memory device that one can write data to and read data from.
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Ras - Acoustical equivalent of Rms
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Re - "This is the DC resistance of the driver measured with an ohm meter and it is often referred to as the 'DCR'. This measurement will almost always be less than the driver's nominal impedance. Consumers sometimes get concerned the Re is less than the published impedance and fear that amplifiers will be overloaded. Due to the fact that the inductance of a speaker rises with a rise in frequency, it is unlikely that the amplifier will often see the DC resistance as its load."
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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).
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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.
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Res - The electrical resistive equivalent of Rms, in ohms
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Resistance - The opposition to the flow of AC or DC voltage in an electric current. Measured in ohms.
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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.
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Resonance - Pitch. When you tighten a drum, you raise it's resonance.
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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.
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Revc - DC voice coil resistance, in ohms
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Revc - DC voice coil resistance, in ohms
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RF Modulator - A device that converts a signal (typically audio and/or video) into a radio frequency.
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Rg - Amplifier source resistance (includes leads, crossover, etc.), in ohms
?/SPAN>Rg - Amplifier source resistance (includes leads, crossover, etc.), in ohms
?/SPAN>RMS - Root Mean Square.
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Rms - "This parameter represents the mechanical resistance of a driver suspension losses. It is a measurement of the absorption qualities of the speaker suspension and is stated in N*sec/m." The driver's mechanical losses, in kg/s
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Roll-Off - Relates to the attenuation of frequencies, above or below a given point, at a specific rate.
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ROM - Read Only Memory. A memory device that one can only read data from. The data has been pre-programed.

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.
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Sampling - Measuring the analog signal at a fixed rate of speed (sampling frequency).
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Sd - Effective piston radiating area of driver, in square centimeters. "This is the actual surface area of the cone, normally given in square cm."
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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.
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Selectivity (alternate channel) - Similar to capture ratio, but deals with signals which are broadcast on frequencies very close to the one selected.
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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.
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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).
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Separation - The degree to which left and right channels in a stereo signal can be kept apart.
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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.
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Shield - A metallic foil or braided wire layer surrounding conductors which is designed to prevent electrostatic or electromagnetic interference from external sources.
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Signal - Any electrical transmittance that conveys data.
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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 dBTimes Signal is Greater than Noise
3.16
10.00
31.62
100.00
316.20
1,000.00
3,162.00
10,000.00
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Slope - The rate of boost or attenuation expressed in decibels of change per octave.
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Sound - A wave propagated in air producing an auditory sensation in the ear by the change of pressure at the ear.
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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)].
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Sound Pressure Level (SPL) - An acoustic measurement of sound energy, typically expressed in dB SPL.
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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.
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SPDT - Single Pole Double Throw. A relay that has only one pole or contact but whose contact can throw or make electrical contact with two separate stationary contacts.
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Speaker - A transducer which converts electrical energy into acoustical energy (sound).
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Spectrum Analyzer - A device that displays a frequency response curve, in real time, as the curve, changes.
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SPST - Single Pole Single Throw. A relay that has only one pole or contact and can only throw or make electrical contact with one stationary contact.
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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.
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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.
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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.
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Subcode - 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.
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Sub-woofer - A loudspeaker made to reproduce the lowest of audio frequencies, approx. 25 Hz to 125 Hz.
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Supertweeter - A high frequency driver designed to reproduce very high frequencies, typically over 10 kHz.
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Switch - A switch is any form of mechanical, electronic, electromechanical, magnetic, or mercury device that either opens or closes a circuit

T-


Tera (T) - A prefix meaning 1012 or 1,000,000,000,000 (one trillion in the US).
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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.
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TOC / Table Of Contents - The subcode information which contains track numbers and times.
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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.
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Total Harmonic Distortion (THD) - The noise referenced to signal in decibels (dB) as a percentage.
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%
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Tracking Servo - The control circuit used to keep the pick-up over the desired track.
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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.
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Transformer - An electrical device that can be used to provide circuitry isolation, signal coupling, impedance matching, or voltage step-up .
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Transistor - A three terminal device used for amplification and switching.
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Tuner - A component (or section of one) that receives radio signals and selects one broadcast from many.
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Tweeter - A high frequency driver specifically designed to reproduce only the high frequencies (treble) of the audible spectrum.

U-

Underlap - The crossover point being more than 3 dB below the unattenuated level.
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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 (it vibrates out of control); the speaker will exhibit low power handling at lower frequencies.

V-


Vas - Compliance. A measurement in liters or cubic feet of the volume of air that is equal to the compliance of the speaker's total suspension.
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Vas/Cms - "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. "Vas represents the volume of air that when compressed to one cubic meter exerts the same force as the compliance (Cms) of the suspension in a particular speaker. Vas is one of the trickiest parameters to measure because air pressure changes relative to humidity and temperature ?a precisely controlled lab environment is essential. Cms is measured in meters per Newton. Cms is the force exerted by the mechanical suspension of the speaker. It is simply a measurement of its stiffness. Considering stiffness (Cms), in conjunction with the Q parameters gives rise to the kind of subjective decisions made by car manufacturers when tuning cars between comfort to carry the president and precision to go racing. Think of the peaks and valleys of audio signals like a road surface then consider that the ideal speaker suspension is like car suspension that can traverse the rockiest terrain with race-car precision and sensitivity at the speed of a fighter plane. It quite a challenge because focusing on any one discipline tends to have a detrimental effect on the others. "
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Vd - Maximum linear volume of displacement of the driver (product of Sd times Xmax), in cubic meters. "This parameter is the Peak Diaphragm Displacement Volume ?in other words the volume of air the cone will move. It is calculated by multipying Xmax (Voice Coil Overhang of the driver) by Sd (Surface area of the cone). Vd is noted in cc. The highest Vd figure is desirable for a sub-bass transducer."
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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.
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Volt - The unit of measure for electrical potential.
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Voltage - he difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit.
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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
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VOM - Volt-Ohm-Meter. A multimeter that measures voltage, resistance (ohms), and amperes, milliamperes


W-


Watt (wattage) - A measurement of real power. The product of voltage and current in a resistive circuit.
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Wavelength - The length of distance a single cycle or complete sound wave travels.
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White Noise - Noise in which a constant energy level per unit (1 Hz) is maintained in all frequencies.
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Woofer - A loudspeaker made to reproduce the lower range of the audio spectrum (bass), in a 2-way or more complex speaker system.
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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.
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Xmax/Xmech - Maximum peak linear excursion of driver, in meters. "Short for Maximum Linear Excursion. Speaker output becomes non-linear when the voice coil begins to leave the magnetic gap. Although suspensions can create non-linearity in output, the point at which the number of turns in the gap (see BL) begins to decrease is when distortion starts to increase. Eminence has historically been very conservative with this measurement and indicated only the voice coil overhang (Xmax: Voice coil height minus top plate thickness, divided by 2). Xmech is expressed by Eminence as the lowest of four potential failure condition measurements times 2: Spider crashing on top plate; Voice coil bottoming on back plate; Voice coil coming out of gap above core; Physical limitation of cone. Take the lowest of these measurements then multiply it by two. This gives a distance that describes the maximum mechanical movement of the cone."


Y-


Yocto (y) - A prefix meaning 10-24 or 0.000 000 000 000 000 000 000 001
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Yotta (Y) - A prefix meaning 1024 or 1,000,000,000,000,000,000,000,000

Z-

Zepto (z) - A prefix meaning 10-21 or 0.000 000 000 000 000 000 001
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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.
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Zero Output - The absence of output signal or output power.
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Zetta (Z) - A prefix meaning 1021 or 1,000,000,000,000,000,000,000
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Zmax - This parameter represents the speaker impedance at resonance
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Zobel - A filter used to stabilize speaker impedance at a crossover frequency where impedance has risen to twice the nominal impedance.
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Zone - A specific area of a security system's coverage. A specific trigger input of an alarm.
 
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