| A-B Test | Evaluating comparative performance of two or more amplifiers or speaker systems by listening and switching quickly from one to the other. |
| Absorption | The ability of a room to take up or absorb the acoustic energy radiated within it. |
| Acoustic | Relating to, containing, producing, arising from, actuated by, or carrying sound. Pertaining to the act or sense of hearing, the science of sound, or the sound heard. |
| Active | A type of circuitry that can increase the gain or amplitude of a signal. |
| Ampere | A unit of measurement of electrical current |
| Amplifier | (AMPL) A device capable of increasing the magnitude or power level of a voltage or current that is varying with time (frequency), without distorting the wave form of the signal. The amplifier is, just as the word implies, a signal amplifier. The incoming signal from any program material source is far too weak to power a speaker system. The role of the amplifier is to take that weak signal and strengthen it to the necessary power level to operate the loudspeakers with minimal distortion. |
| Attenuation | The reduction in level of a signal. |
| Audio Chain | The order of sequence for connecting audio components, i.e. microphone, preamplifier, (mixer), effects device, graphic equalizer, crossover, amplifier, and speaker. |
| Audio Range | 20 Hz to 20,000 Hz. (Twenty cycles per second to twenty thousand cycles per second). The frequency response spectrum of human auditory perception. |
| Aux Input | An auxiliary input that serves as a straight connection to a signal BUS (for instance: Monitor Aux input to the monitor BUS.) |
| Baffle | The panel on which the speaker is mounted within the speaker enclosure. The term derives from its original use in preventing or baffling the speaker's rear sound waves from interfering with its front waves. |
| Balanced Cable | A pair of wires surrounded by a braided shield. |
| Balanced Line | A transmission line consisting of two conductors plus a braided shield, capable of being operated so that the voltages of the two conductors are equal in magnitude (voltage) and opposite in polarity with respect to ground. |
| Bandwidth | Response characteristic in which a definite band of frequencies having a low frequency and high frequency limit are transmitted or amplified uniformly. |
| Bass Reflex | A type of speaker enclosure in which the speaker's rear sound wave emerges from a critically dimensioned auxiliary opening or port to reinforce the bass tones. |
| Bi-Amp | Separating the audio spectrum into two bands, i.e. high frequencies (high pass) and low frequencies (low pass) by means of an electronic crossover and using two separate amplifiers or channels of an amplifier; one amp or channel is used to amplify and project the high pass signals form the high frequency component or horn of the speaker system and the other amp or channel amplifies the low pass signals and projects them from the woofer or low frequency component of the speaker system, resulting in increased headroom and dynamic range. |
| Boost | A term used to indicate an increase in gain of a frequency or band of frequencies when equalizing an audio signal. |
| Bridging | Connecting one electrical circuit in parallel to another. Example: Paralleling power amplifier inputs. |
| BUS | A conductor that serves as a common connector to several signal sources, always associated with a mix amplifier. |
| Capacitor | A device which consists essentially of two conductors (such as parallel metal plates) insulated from each other by a dielectric (a material in which an electric field can be sustained with a minimum dissipation in power) and which introduces capacitance into a circuit, stores electrical energy, blocks the flow of direct current (DC), and permits the flow of alternating current (AC), to a degree dependant on the capacitor's capacitance and the current frequency. |
| Cardoid | A type of microphone having a heart shaped pickup pattern that picks up sound better from front than back. |
| Clipping | Amplifier overload causing a squaring off or undesirable change in the wave form resulting in distortion or perceptible mutilation of audio signals. |
| Common Mode Rejection | The ability of an amplifier to cancel a common mode signal (such as interference) that is applied equally to both ungrounded inputs of a balanced amplifier, while responding to an out-of-phase signal. |
| Compression | Reduction of the effective gain of an amplifier at one level of signal with respect to the gain at a lower signal level. |
| Conductor | A wire, cable or other material suitable for carrying electrical current. |
| Continuous Power | This power rating represents the most conservative statement of the capability of an amplifier. It is also called "RMS" power. It denotes the amount of power an amplifier can deliver when amplifying a constant steady tone. It is usually measured at a signal frequency of 1000 Hz for a specific distortion. |
| Continuous Program Material | A signal, such as speech or music, that contains voltages continuously changing in both frequency (time) and amplitude (voltage). |
| CPS | Abbreviation for "cycles per second", the units for expressing frequency. The term "CPS" has been obsoleted and replace by "Hertz". |
| Critical Distance | The point within a room where the sound level of the direct field radiating from the loudspeaker and the reverberant field within the room become equal in intensity or level. |
| Crossover | See "Basic Training: Crossovers" |
| Current (I) | The rate of flow (measured in amperes) of electricity in a conductor or circuit. |
| Cut | A term used to indicate the reduction in gain of a frequency or band of frequencies when equalizing an audio signal. |
| Cycle | A unit of motion referenced to a time period of one second. The frequency of a vibration or oscillation in units per second. 100 Hz or 100 c.p.u.'s (cycles per second) refers to the number of times per second (100) a string is vibrated or an amplifier is swinging positively and negatively. |
| Damping Factor | The ratio of the speaker impedance to the amplifier's internal output impedance. Damping factor is a measure of how well an amplifier can actually control the movement of a speaker cone or diaphragm by preventing it from moving farther than it is supposed to. Damping factor is arrived at by dividing the speaker impedance by the amplifier's output impedance. Anything connected in the speaker line, including the speaker cable itself, or a crossover looks to the speaker like an increase in the output impedance of the amplifier, thus lowering the effective damping factor. Because any speaker is a mechanical device, it will have its own resonant frequencies which will cause the cone to continue in motion after a musical signal has stopped. (See transient distortion.) An amplifier with a high damping factor will damp out these speaker tendencies. |
| dB (Decibel) | A unit for describing the ratio of two voltages, currents, or powers. The decibel is based on a logarithmic scale. When measuring differences in sound pressure level (SPL), the amount of change in sound pressure level perceivable is directly proportional to the amount of stimulus (the more sound present, the greater the change must be, to be perceived.) |
| dBm | A decibel scale referenced to OdBm=1 milliwatt into 600 ohms or .773 volts RMS |
| dBv | A decibel scale reference to 1 volt RMS; OdBv=1 volt |
| Differential Amplifier | An amplifier whose output is proportional to the difference between the voltages applied to its two inputs. |
| Diffraction | The bending or redistribution of acoustic sound waves in a room caused by some obstacle, such as a column or divider. Only low frequency wave forms can be diffracted. |
| Dip | A reduction in gain at a certain frequency; also called a notch. |
| Directivity | Area of coverage of a speaker or microphone. |
| Directivity Factor | The ratio of radiated sound intensity at a remote point on the principal axis of a loudspeaker to the average intensity of the sound transmitted through a sphere passing through the remote point and concentric with the transducers; the frequency must be stated. |
| Dispersion | The spread or distribution or coverage of sound generated from a horn or loudspeaker. For any given frequency, the area of dispersion is defined as that area between the -6dB down point or that frequency plotted against amplitude. It is measured in degrees related to an imaginary line descending from the center of the speaker cone. As you move away from the imaginary line, up or down, right or left, the loudness level of the sound increases. When the sound level decreases rapidly on either side of the imaginary line, the dispersion in degrees is relatively small and the speaker is said to be highly directional. |
| Distortion | Any undesired change in the wave form of an electrical signal passing through a circuit or transducer. Any distortion can be defined as deviation from the original sound, the discrepancy between what the amplifier should do and what it actually does. All distortion in undesirable. The amplifier alters the original sound in the process of amplification so that what comes out of an amplifier is no longer a true replica of what went it. Performers, however, will sometimes desire the application of electronically induced distortion for extra-musical effect. The undesirability of inherent distortion is associated with high fidelity and should not be confused with the desirability of distortion as it is expected to be produced through circuitry. |
| Dynamic Range | In a musical instrument, the dynamic range is the difference in decibels between the loudest and softest level of notes that can be played on that instrument. In electronic equipment, dynamic range is the difference in decibels between the highest (overload level) and lowest (minimum acceptable) level compatible with that signal system or transducer. |
| Efficiency | The ratio, usually expressed as a percentage, of the useful power output to the power input of a device. |
| Electronically Balanced Input | A differentially balanced amplifier; an amplifier whose output is proportional to the difference between the voltages applied to its two inputs. |
| Enclosure | An acoustically designed housing or structure for a speaker. |
| Equalization | The act of obtaining a desired overall frequency response through the implementation of graphic equalizers or tone controls. |
| Excursion | Movement of the cone of a loudspeaker or the diaphragm of a compression driver. |
| Exponential Horn | A speaker designed to reproduce the high frequencies. An exponential horn has a flare rate that increases with the square of the distance from the entry to the horn throat. |
| Feedback | Electronic: The return of a portion of the
output of a circuit to its input. Acoustic: The regeneration of a signal from the output of a sound system into a microphone input. |
| Filter | An electrical or electronic device that permits certain frequencies to pass while obstructing others such as a crossover filter used with loudspeakers. |
| Frequency | The number of vibrations or oscillations in units per second. Measured in cycles or hertz per second. The rate of repetition in cycles per second (Hertz) of musical pitch as well as of electrical signals. For example, the number of waves per second a vibrating device such as a piano or violin string moves back and forth in each second of time to produce a musical tone. |
| Frequency Response | A measure of the effectiveness with which a circuit, device or system transmits the different frequencies applied. The way in which an electronic device (microphone, amplifier or speaker) responds to signals having a varying frequency. This is a measurement of how well an amplifier reproduces and amplifies a specified audible range with equal amplitude or intensity, as an example, 30 - 16,000 kHz. |
| Full Range | The entire audio spectrum, 20 Hz - 20 kHz. |
| Gain | An increase in strength or amplitude of a signal. The increase in signal power that is produced by an amplifier; usually given as the ratio of output to input voltage, current, or power expressed in decibels. |
| Ground Loop | Hum caused by return currents or magnetic fields from relatively high-powered circuits or components which generated unwanted, noisy signals in the common return of relatively low-level signal circuits. A potentially detrimental loop formed when two or more points, in an audio system that are nominally at ground potential, are connected by a conducting path. |
| Harmonic | One of a series of sounds, each of which has a frequency which is an integral multiple of some fundamental frequency. |
| Headroom | The difference between the average operating power level of an amplifier circuit and the point at which clipping or severe distortion occurs. |
| Hertz (Hz) | A unit of measurement, previously referred to as cycles per second used to indicate the frequency of sound or electrical wave. A unit of motion referenced to a time period of one second. The frequency of a vibration or oscillation in units per second. |
| High Pass | All signals above a given crossover frequency. |
| High Z or High Impedance | Any resistance to AC voltage or current generally greater than 2,000 ohms. |
| Hum | Hum from the 120 volt, 60 cycle power line, either its actual frequency or the harmonics of it, that intrudes into the amplified sound and mars listening quality. |
| IM (Intermodulation Distortion) | Non-linear distortion characterized by the appearance of output frequencies equal to the sums and differences of integral multiples of the input frequency components. For instance, an amplifier with high IM distortion amplifying two frequencies of 100 Hz and 2,000Hz would also generate distortion components of 19,000 kHz and 2,100 Hz. |
| Impedance | The total opposition to alternating current flow presented by a circuit. The resistance to the flow of alternating current in an electrical circuit, generally categorized as either "high" or "low", but always expressed in ohms. Commonly used to rate electrical input and output characteristics of components so that proper "match" can be made when interconnecting two or more devices, such as a microphone, loudspeaker or amplifier. |
| Impedance Match | The condition in which the external impedance of a connected load is equal to the internal impedance of the source, thereby giving maximum transfer of energy from source to load, minimum reflection, and minimum distortion. |
| Inductance | That property of an electric circuit or of two neighboring circuits whereby an electromotive force is generated (by the process of electromagnetic induction) in one circuit by a change in current in itself or in the other. |
| Inductor | A coil of wire used to create an impedance whose reactive component is low therefore offering low resistance at low frequencies and high resistance at high frequencies, i.e., an inductor passes low frequencies and attenuates or rolls off high frequencies. |
| Infinite Baffle | A baffle that effectively prevents all of the loudspeaker's rear sound waves from interfering with its front waves. |
| Input Overload | Distortion produced by too strong a signal from the output of a microphone or other signal source such as a keyboard connected to the input of a preamplifier. |
| Integrated | A type of design in which two or more basic components or functions are combined physically as well as electrically, usually on one chassis as opposed to a separate mixer and power amplifier. |
| Jack | A receptacle on a receiver, tape recorder, amplifier or other component into which a mating connector can be plugged. |
| Kilohertz (khz) | A frequency of one thousand cycles per second |
| Light Emitting Diode (LED) | A semiconductor device that produces visible light when a voltage of a certain polarity and potential is applied to it. |
| Limiter | An electronic circuit used to prevent the amplitude of an electronic waveform from exceeding a specified preset level while maintaining the shape of the waveform at amplitudes less than the preset level. |
| Line Out | An output connection found on mixers and preamps providing an output at a level sufficient to drive the input of a power amplifier. |
| Load Impedance | The actual impedance of the load or speaker that a power amplifier is connected to, thus driving a load of a certain impedance. |
| Low Pass | All of the frequencies below a given crossover frequency. |
| Loudness Control | A volume control with special circuitry added to compensate for the normal decreased hearing ability of the human ear at the extreme ends of the audio range when listening to lower sound levels. A typical loudness control boosts the bass tones and to a lesser extent, the treble tone. This is not frequently applied to high fidelity equipment. |
| Loudspeaker Efficiency | The ratio, expressed in percentage, of signal output to signal input used to state the power needed to drive a loudspeaker. For example: Power output: 2 watts / Power input: 10 watts = 20% efficiency. Efficiency can vary from 2% to as high as 25%. |
| Low Z or Low Impedance | Any resistance to AC voltage or current flow generally less than 2000 ohms. |
| Master | Main level or gain control for a BUS or mix. |
| Music Power | This is a power rating generally applied to high fidelity amplifiers for tones of short duration. It takes into account the fact that most amplifiers can produce a greater amount of power in short bursts than they can continuously. The rationale is that music is made up of such bursts rather than sustained single frequencies. It is higher than continuous power ratings for those same amplifiers. It is measured at a single frequency of 1000 Hz for a specified distortion. |
| Noise | Any extraneous sound or signal that intrudes into the original as a result of environmental noise, distortion, hum, or defective parts in the equipment. |
| Notch Filter | A band rejection filter that produces a sharp notch in the frequency response of a system, thus reducing the gain or amplitude of a narrow band of frequencies centered on a given frequency. |
| Octave | The interval between any two frequencies having a ration of 2 to 1. Example: "A 440" is an octave above "A 220". |
| Ohm | The unit of electrical resistance, equal to the resistance through which a current of one ampere will flow when there is a potential difference of one volt across it. Ohm is the unit of measure used to express opposition to current flow. Every wire or part through which electricity passes has some resistance to that passage. |
| Omnidirectional | Applied to microphones to refer to uniform pick up of sound from all directions. |
| Output Impedance | The internal output impedance of an amplifier presented by the amplifier to the load. (Output impedance is many times used incorrectly instead of load impedance.) |
| Overtone Harmonic | Multiples of frequency of a fundamental waveform. |
| Pad | A fixed passive network which reduces the electrical level of a signal. |
| Parallel | An electric circuit in which the elements or components are connected between two points with one of the two ends of each component connected to each point. |
| Parametric | A type of equalization circuit that has three variable parameters: frequency; cut or boost; and bandwidth or Q. |
| Passive | An electronic circuit composed of passive elements, such as resistors, inductors, or capacitors, without any active elements, such as vacuum tubes or transistors generally resulting in a signal loss. |
| Peak | The maximum instantaneous value of a signal amplitude. |
| Peaking | A term used to indicate an increase in gain of a frequency or band of frequencies when equalizing an audio signal. |
| Peak Power | Used by manufacturers in an attempt to "look better" in print and has no bearing on the actual performance of a product. (Usually peak power works out to be twice continuous power. Some of these same manufacturers have come up with yet another power term referred to as "Instantaneous Peak Power", which is a further inflated and equally meaningless specification. Amplifier power should be judged on an equal basis when comparing one amplifier with another. |
| Peak-to-Peak | Amplitude of an alternating voltage measured from negative peak to positive peak. |
| Phase | The time interval between two related events. Two signals are in phase when they reproduce the same sound or signal simultaneously; they are out of phase to the extent that one leads or lags behind the other in time. A signal is said to be in phase with another when the voltage and current amplitudes begin at the same time and move in the same direction. |
| Phase Cancellation | Signals that are out of phase will cancel one another according to the difference in phase in degree. A transducer (speaker or microphone) wired out of phase with another will result in reduced output from both; instead of their combined outputs adding, they will subtract due to phase cancellation. |
| Piezo-Electric | Having the ability to generate a voltage when mechanical force in applied; or to produce a mechanical force when a voltage is applied, as in a Piezo-Electric crystal. |
| Polarity | The quality of having opposite poles. In electro-magnetic mechanical systems, some form of potential is referenced to one of two poles with different (usually opposite) characteristics, such as one which has opposite charges or electrical potentials, or opposite magnetic poles. |
| Post | (After) On a mixer, indicates that the function is derived after the channel slider or gain control; i.e., post EQ the equalization (EQ) network is after the channel slider or gain control. |
| Power | Electrical energy, measured in watts, such as the current from an amplifier used to drive a loudspeaker. |
| Power Amplifier | The final active stage of the audio chain, designed to deliver maximum power to the load or speaker impedance for a given percent of distortion. |
| Pre | (Before) On a mixer, indicates that the function is derived before the channel slider or gain control; i.e., pre EQ, the EQ network is before the channel slider ; pre monitor send, the monitor send is before and independent of the channel slider or gain control. |
| Preamp (Preamplifier) | An amplifier whose primary function is boosting or amplifying the output of a low-level audio frequency source (such as a microphone), so that the signal may be further processed without appreciable degradation of the signal-to-noise ratio of the system. An amplifier which increases electrical signals from a microphone or other instrument to a level usable by the power amplifier. |
| Preamp Out | A means of obtaining an output signal from the preamplifier of a channel of a mixer or musical instrument amplifier. |
| Proximity Effect | Increase in low frequency response when a proximity effect microphone is used close to a sound source. |
| Real Time Analyzer (RTA) | An electronic instrument used to measure the combined response of an audio system and the room in which the system is operating. |
| Reflection | The bouncing back or return of sound waves from walls or other obstacles which they strike. |
| Resistance | Opposition to the flow of electrical current. |
| Resistor | An electronic component designed to have a definite amount of resistance; used in circuits to limit current flow or to provide a voltage drop. |
| Resonance | A tendency of mechanical parts, loudspeaker cone, enclosure panels or electrical circuits to vibrate or emphasize at one particular frequency every time that frequency, or one near it, occurs. |
| Response | The range of frequencies to which an amplifier or speaker will respond, and the relative amplitude or intensity with which these frequencies are reproduced. |
| Return | An input used to patch a signal returning to a particular BUS after having been further processed, such as an echo or effects return. |
| Reverb or Reverberation | Acoustical: The prolongation of sound at a given
point after direct sound from the source has ceased, due to such causes as
reflection from physical boundaries. Electro-mechanical: A device usually employing springs which randomly reflect as great amount of sound as possible; therefore, simulating natural reverberation. |
| RIAA | Stands for Recording Institute Association of America. A type of preamplifier used for turntables. It is necessary to use an RIAA preamp when using a magnetic cartridge. |
| Ring Mode | A tone or frequency sounded in a room with a live sound reinforcement system prior to the system breaking into feedback. A ring mode lies just below the threshold of feedback. |
| RMS | Root means square value. The square root of the time average of the square of a quantity; for a periodic quantity the average is taken over one complete cycle. RMS voltage is .707 times the peak voltage of a sine wave. |
| Roll Off | A signal is rolled off when it is attenuated or reduced in level above (high pass roll off) or below (low pass roll off) a certain frequency. The amount of roll off is rated at so many decibels per octave. A signal that is rolled off below 100 Hz at a rate of 18 dB/octave would be reduced in level or attenuated -18 dB at 50 Hz, -36 dB at 25 Hz, etc. |
| Send | An output used to patch a signal from a channel or BUS of a mixer to an external signal processor such as an echo or digital delay. |
| Sensitivity | The minimum input signal required to produce a specified level of output. In an amplifier, the input sensitivity is the amount of voltage at the input necessary to drive the amplifier to its rated power output. |
| Series | An arrangement of circuit components, end-to-end, to form a single path for current. |
| Series (Parallel) | A circuit in which some of the components or elements are connected in parallel, and one or more of these parallel combinations are in series with other components of the circuit. |
| Shelving | A type of equalization circuit that has a shelf-like characteristic at the upper or lower ends of the spectrum. |
| Sine Wave | A wave whose amplitude varies as the mathematical sine of a linear function of time, also, known as the sinusoidal wave. |
| Signal-to-Noise Ratio (S/N) | The ratio of the amplitude or level of a desired signal at any point to the amplitude or level of noise at the same point. |
| Snake | A multi-conductor shielded input cable employed when necessary to locate a mixer a long distance from the stage and the microphones. |
| Slew Limiting | The failure of the amplifiers output to move as fast, voltage-wise, as the input would have it move. |
| Slew Rate | The ability of an amplifier's output to accurately reflect the input waveforms rise time transients. An amplifier is said to have a slew rate of so may bolts per micro second. A slew rate of 20 volts per micro second (20 V/U sec.) means that the amplifier is capable of swinging 20 volts positive or negative in the period of one micro second. |
| Sound Level Meter | An instrument used to measure noise and sound pressure levels (SPL), calibrated in decibels. |
| Sound Pressure Level (SPL) | The level or intensity at a point in a sound field (loudness). The deviation above and below normal atmospheric pressure. |
| Splitter | A box into which one microphone or signal is connected and has two or more individual outputs available for the signal. |
| Stereo | In a sound reproducing system, stereo refers to the use of two separate signal processing channels driving two separate power amplifiers which, in turn, powers two separate speaker systems. However, most times in sound reinforcement, a stereo mixer is employed to drive a mono (single channel) system in order to have submixes. (separate instruments vs. vocal mixes of the program). |
| Sub-Master | A level control preceding the main (master) level control, that regulates the level of an individual sub-mix. |
| Sub-Mix | A separate mixing BUS assigned to a group of instruments (drums, brass, strings) or vocals that enables the sound mixer to regulate the level of that group with one control called the submixer. |
| Switching Jack | An input jack that performs some switching function in addition to providing an input for a signal. |
| Total Harmonic Distortion (THD) | When a single frequency of specified level is applied to the input of a system, the ratio of the voltage of the fundamental frequency to the voltage of all harmonics observed at the output of the system because of the non-linearities of the system; THD is expressed in percent. |
| Transducer (XDCR) | Any device or element which converts an input signal into an output signal of a different form. A transducer changes energy from one form to another. A microphone is a transducer that changes acoustical energy (sound) into electrical energy (voltage). A loudspeaker is a transducer that changes electrical energy in to mechanical energy producing sound or acoustical energy. |
| Transformer (XFMR) | An electrical component consisting of multi-turn coils of wire placed in a common magnetic field (medium) which will transfer electrical energy from one electrical circuit to the next. A transformer will only pass alternating currents (AC) and will not pass direct current (DC). By adjusting turn ratios, a step up or down condition of voltage can be achieved. |
| Transformer Balanced (XFMR BAL) | An input or output that is coupled by means of a transformer in a configuration that makes it balanced or capable of being operated so that the voltages of the two conductors at any transverse plane are equal in voltage and opposite in polarity with respect to ground. A transformer common-mode interference signal will not pass through the transformer because it will be cancelled out. |
| Transient | Rapidly changing peaks of short duration in the level of musical instruments such as a cymbal crash or a rim shot on a snare drum. A wave having a very short or no sustain time. |
| Transient Distortion | Interferes with the ability of an amplifier to follow accurately abrupt changes in volume, such as the sudden burst of sound when an instrument is first played. Minimum transient distortion is vital to clean and crisp overall sound. |
| Tri-Amp | Separating the audio spectrum into three bands, i.e., high frequencies, mid-band frequencies and low frequencies, by means of an electronic crossover and using three separate power amplifiers to amplify the three outputs of the crossover (high pass, mid pass, low pass outputs) driving three separate components of a speaker system, resulting in increased headroom and dynamic range. |
| Unbalanced Cable or Line | A single conductor cable with a surrounding shield that connects to ground. Such a system is called unbalanced because it cannot be balanced or offer common mode rejection. |
| Unbalanced Input | An input in which one of the two terminals is ground potential or connected to the chassis ground. |
| Voltage | A measurement of electrical pressure. The familiar 120 volts at the wall socket is an example of available electrical pressure. If the prefix "M" is used (as in "MV") it stands for millivolts - thousandths of volts. Microvolts, abbreviated "uV" refers to millionths of volts. |
| Volts | Potential difference of electromotive force. |
| Volume | The intensity or loudness of sound. |
| Volume Unit (VU) | A unit for expressing the audio frequency power level of a complex electronic waveform such as that corresponding to speech or music. "0" VU is referenced to 1 milliwatt of power. |
| VU Meter | A meter which indicates the audio frequency power level or volume units of a complex electronic waveform. |
| Watt | A unit of measure of power. The electrical wattage of an amplifier describes the power it can develop to drive a speaker. The greater the voltage capability, the higher the wattage. Amplifier wattage requirements are greatly dependent upon the speakers that will be used, the size of the listening room and average loudness that will be played through the speakers. |
| Woofer | A low frequency speaker specialized in bass reproduction. |
| XLR | A connector (sometimes called a cannon connector) used in interfacing audio components. The connector on a low impedance microphone is an XLR connector. |
| 0dB | In the measurement of SPL or Sound Pressure Level, 0dB is referenced to the threshold of hearing or auditory perception of a tone of 1000 cycles (hertz) per second. |
| 3dB | The amount of SPL gained by doubling the power to a speaker. The amount gained by doubling the number of speakers. |
| ±3dB | Measurement of frequency response that exhibits no more than +3dB above and no less than -3dB below a given reference. It is actually a 6dB window. The response of 60 Hz to 14 kHz ±3dB means that within the bandwidth of sixty cycles per second to fourteen thousand cycles per second, no frequency is +3dB more nor -3dB less than a specified frequency. |
| 3dB Down | The point at which a measured power level is 3dB below the specified level. In an electronic crossover, the point (frequency) at which the high pass signal is -3dB down in response or power level is considered the crossover point (frequency). |
| -6dB | The amount of loss in SPL as you double the distance away from a sound source. |