AC: Alternating current. Energy that changes potential at a fixed or regulated rate. The electricity in a home and a musical signal going to a speaker are examples of alternating current.
ACOUSTICAL ENERGY: Energy created by sound waves.
A-B (or A/B Test): Listening comparison between two audio sources playing the same program, performed by switching immediately from one to the other.
AMPERAGE: Rating designating the quantity of electricity flowing through a circuit. Unit of measure is the ampere (amp).
AMPLIFICATION: An increase in signal level.
AMPLITUDE: Measurement of the power of a sound or electrical wave.
ATTACK: The beginning of a note. The first portion of a note's envelope, in which a note rises from silence to its maximum volume.
ATTENUATE: To reduce the force or volume of a signal.
ATTENUATOR: Control or switch found on the rear input panel of SWR speaker enclosures used to adjust the level of high-frequency signal present at the tweeter.
AUDIO FREQUENCY SPECTRUM: The range of human hearing, commonly defined as 20 Hz to 20,000 Hz.
AURAL ENHANCER™: A SWR tone-shaping control that brings out fundamental low notes, reduces certain frequencies that help mask the fundamentals, and enhances high-end transients. The Aural Enhancer is a passive R/C network that alters the frequency response throughout the frequency spectrum. This pre-shaping is then "blended" into the original signal using the Aural Enhancer control. Exact frequencies affected depend on the characteristics of the instrument used. The result is a more "transparent" sound.
AUDIO SIGNAL: Electronic representation of a sound wave.
BAFFLE, BAFFLE BOARD: Board to which speakers are mounted in a box.
BANDWIDTH: Upper and lower usable frequency limits of a device.
BASKET: Outside frame of a speaker; supports the cone and magnet.
BASS: Low-frequency (below 500Hz) audio signals.
BASS INTENSIFIER™: A proprietary feature on many SWR amplifiers designed after 2003; the Bass Intensifier is a low-end boost circuit combined with a smooth, fast-acting compressor. The Bass Intensifier provides radical low frequency boost without overdriving the amplifier, which can be useful for heavier sections of a song - or just for "fattening up" the overall tone of your bass.
BASS REFLEX: Vented or ported speaker enclosure.
BALANCED LINE: Cable with two conductors surrounded by a shield, with each conductor at equal impedance to ground. With respect to ground, the conductors are at equal potential but opposite polarity.
BI-AMPLIFICATION: Or "bi-amping." Driving a woofer and tweeter with separate power amplifiers. An active crossover is connected ahead of these power amplifiers to route signals properly.
BRIDGING: Combining the outputs of two amplification channels to provide a single, more powerful channel.
CAPACITANCE: Property of storing an electrical charge between two separate conductors.
CAPACITOR: Electronic device that can store energy and release it as needed. Capacitors works by resisting changes in voltage, making them useful in crossover circuits. Capacitors are rated in "farads" (or, more commonly , microfarads or millionths of a farad).
CHANNEL: Single path of an audio signal.
CHASSIS: Aluminum (or other metal) structure that houses the electronic components of an SWR amplifier.
CHORUS: Wavy-sounding multiple-voice effect in which a signal is delayed by 15 to 35 milliseconds and then combined with the original signal, with the delay varied periodically.
CLEAN: Free of noise and distortion. Not muddy.
CLIPPING: Signal distortion generated by an amplifier being operated over its capabilities. Clipping describes the actual "cutting off" of signal peaks of an electrical signal at the amplifier's power limit. This is the "breaking up" sound often heard when a system is played too loud. Clipping distortion is the most common source of speaker damage.
COMPRESSION: Reduction in dynamic range.
COMPRESSOR: Signal processor that reduces dynamic range by means of automatic volume control. Decreases gain as the input signal level increases above a pre-set point.
CONE: The part of a speaker that moves.
CROSSOVER: Electronic network that divides an incoming signal into two or more frequency bands.
CROSSOVER FREQUENCY: Single frequency at which both filters of a crossover network are down 3 dB.
DAMPING: Reduction of resonant energy in a speaker, or between a speaker and amplifier.
DC: Direct current. Power derived from a battery or rectified source in which electrons flow only in one direction.
DC RESISTANCE: Resistance a device produces for a DC current. Direct measurement by a digital multimeter or a volt/ohm meter gives DC resistance.
DECIBEL: Unit of audio level measurement (volume), abbreviated "dB." Decibels are a logarithmic measure, meaning that doubling the sound output of a system will require 10 times the power (not two times the power).
DIODE: Electronic device that blocks current flow in one direction but allows it in another.
DIRECT BOX: Device used to connect an amplified instrument directly to a mixer mic input. Converts a high-impedance unbalanced audio signal to a low-impedance balanced audio signal.
DIRECT INJECTION: Or "DI." Sending a signal directly to a mixer.
DISCRETE CIRCUITRY: Circuitry using separate components such as resistors, capacitors and diodes, as opposed to integrated circuits that "print" these components in microscopic size on a chip. Discrete components are less heat sensitive and make better-sounding systems.
DISTORTION: Sound that has been changed from the original performance. The three major forms of electronic audio distortion are clipping, harmonic and intermodulation distortion.
DIGITAL MULTIMETER: Or "DMM." A digital meter that measures voltage, current or ohms.
DRIVER: Another name for "speaker."
Dv: Designation for inside diameter of a vent or port.
DYNAMIC RANGE: The difference between the loudest and softest sounds that can be reproduced by a device or format.
EFFECTS: Interesting sound phenomena created by signal processors. Examples include reverb, echo, flanging, chorus, etc.
EFFICIENCY: In a loudspeaker, the ratio of acoustic power output to electrical power input.
E-M: Electro-mechanical parameters of a speaker.
ENVELOPE: Rise and fall in volume, or "shape" of one note. The envelope connects successive peaks of the waves comprising a note. Each harmonic in the note might have a different envelope.
EQUALIZATION: Or "EQ." Adjustment of frequency response in order to alter tonal balance or to attenuate unwanted frequencies.
EQUALIZER: Circuit that alters the frequency spectrum of a signal passed through it.
EXCURSION: Amount of movement a speaker cone is capable of.
EXTENDED POLE PIECE: Design innovation allowing increased excursion while decreasing distortion by operating the voice coil over a longer throw.
Fb: Designation for resonant (tuned) frequency of a vented box. Expressed in hertz (Hz).
Fc: Designation for resonant frequency of a sealed box. Expressed in hertz (Hz).
F3: Designation for half-power (-3 dB) of a speaker enclosure design. Expressed in hertz (Hz).
Fp: Designation for free-air resonant frequency of a passive radiator. Expressed in hertz (Hz).
Fs: Designation for free-air resonant frequency of a driver. Expressed in hertz (Hz).
FARAD: Basic unit of capacitance. Outside of stiffening caps, the most common values of capacitors are microfarads or millionths of a farad.
FEEDBACK: Return of some portion of an output signal to the system's input, often resulting in an unwanted squeal.
FLAT RESPONSE: Ability of a speaker or amplifier to reproduce all points of the frequency band equally, without dips or peaks.
FREE-AIR RESONANCE: Frequency at which a driver will naturally resonate.
FREQUENCY: Number of cycles per second of a sound wave or audio signal, measured in hertz (Hz). A low-frequency sound (i.e., 100Hz) has a low pitch; a high-frequency sound (i.e., 10,000Hz) has a high pitch.
FREQUENCY RESPONSE: Range of frequencies an audio device will reproduce at an equal level (within a tolerance, often +/- 3 dB).
FUNDAMENTAL: Lowest frequency in a complex wave.
FUSE: Device designed to protect other electronic devices by melting and opening the circuit when the system is drawing too much power.
GAIN: Amplification. The ratio, expressed in decibels, between the output voltage and the input voltage, or between the output power and the input power.
GAP: Space between the magnet and the pole piece in a speaker's motor assembly.
GRAPHIC EQUALIZER: Equalizer with a horizontal row of faders that graphically indicate its frequency response. Often used to equalize a speaker enclosure for whatever room it's in.
GROUND: Zero-signal reference point for a system of audio components.
GROUNDING: Connecting pieces of audio equipment to ground. Proper grounding ensures that there is no voltage difference between equipment chassis. An electrostatic shield must be grounded to be effective.
HARMONIC: Overtone with a frequency that is a whole-number multiple of the fundamental frequency.
HARMONIC DISTORTION: Distortion that follows the natural harmonics of the original signal. The least harmful form of distortion.
HEADROOM: Safety margin, measured in decibels, between the signal level and the maximum undistorted signal level.
HERTZ: Cycles per second, the unit of frequency measurement. Abbreviated "Hz."
HIGH FREQUENCY: Audible frequencies generally defined as over 5,000Hz.
HIGH PASS FILTER: Filter that passes frequencies above a certain point and attenuates frequencies below that same point.
HUM: Unwanted low-pitched tone (60Hz, plusharmonics) heard along with an audio signal.
IMPEDANCE: Resistance of a device to the flow of alternating current. Often used to rate resistance of a speaker's voice coil.
INTERMODULATION DISTORTION: Distortion created by a device not harmonic with the original signal. Accordingly, intermodulation distortion is often described as "harsh and grating," and tends to be more noticeable than harmonic distortion. Intermodulation distortion is often the result of poor amplifier design or the use of excessive amounts of negative feedback in the circuit. Systems that are fatiguing to listen to often have high rates of intermodulation distortion.
JACK: A "female" connector that accomodates a phone plug or other "male" connector.
KEVLAR CONES: Kevlar, commonly associated with bullet-proof garments, is an extremely strong and light fiber, making it excellent for speaker cone construction.
KILOHERTZ: Abbreviated "kHz." Thousands of cycles (hertz) per second.
Le: Designation for inductance of a voice coil.
Lv: Designation for length of a vent or port.
LED: Light Emitting Diode.
LED INDICATOR: Level indicator using one or more light emitting diodes.
LEVEL: Degree of intensity of an audio signal; the voltage, power or sound pressure level. The original definition of level encompasses power in watts.
LIMITER: Signal processor with output that is constant above a preset input level. A compressor with a compression ratio of 10:1 or greater, with the threshold set just below the point of distortion of the following device. Prevents distortion of attack transients or peaks; helpful in preventing speaker damage.
LINE LEVEL: In balanced professional recording equipment, a signal with a level of approximately 1.23 volts (+4 dBm). In unbalanced equipment (most home hi-fi or semi-pro recording equipment), a signal with level of approximately 0.316 volts (-10 dBV).
LOUDSPEAKER: Transducer that converts electrical energy (signal) into acoustic energy (sound waves).
LOW FREQUENCY: Generally refers to sounds from 40Hz to 160Hz.
MAGNET: Device at the back of a speaker that provides a stationary magnetic field to attract or repel the voice coil as the signal passes through it.
MONO, MONOPHONIC: Refers to a single channel of audio, as opposed to stereo.
NOISE: Unwanted sound, such as hiss. An audio signal with an irregular, nonperiodic waveform.
NOMINAL IMPEDANCE: The stated impedance rating of a speaker, used to indicate the load a speaker will provide to an amplifier.
OCTAVE: Interval between two frequencies in which the upper frequency is twice the lower frequency (example: 80Hz is one octave above 40Hz).
OUTPUT: Connector in an audio device from which the signal comes, and which feeds successive devices.
OVERLOAD: Distortion that occurs when an applied signal exceeds a system's maximum input level.
OVERTONE: Frequency component of a complex wave that is higher than the fundamental frequency.
OHM: Unit of electrical resistance equal to that of a conductor in which a current of one ampere is produced by a potential of one volt across its terminals.
PAD: See "Attenuator."
PARAMETRIC EQUALIZER: Equalizer having continuously variable parameters, such as frequency, bandwidth and amount of boost or cut.
PARALLEL OPERATION: Connection of two or more power sources of the same output voltage to obtain a higher output current.
PATCH CORD: Short cable used for signal routing.
PEAK OUTPUT CURRENT: Maximum current value delivered to a load under specified pulsed conditions.
PEAK: On a graph of a sound wave or signal, the highest point in the waveform. The point of greatest voltage or sound pressure in a cycle.
PEAK-TO-PEAK: Measured value of a waveform from peak in a positive direction to peak in a negative direction.
PEAK OUTPUT CURRENT: Maximum current value delivered to a load under specified pulsed conditions.
PHANTOM POWER: DC voltage (usually 12 to 48 volts) applied to microphone signal conductors to power condenser microphones. (NOTE: Connecting phantom power to the XLR output on some SWR amplifiers can damage the integrated circuit feeding the XLR output. Please check your owner's manual or call Customer Service if you are in doubt about your particular amplifier's safety in this situation.)
PHASE: Timing of a sound or electrical wave. Phase is measured in degrees, from 0 to 360. 180 degrees is perfectly out of phase, often causing signal cancellation in lower frequencies.
PHASE CANCELLATION: Cancellation of certain frequency components of a signal that occurs when the signal is combined with its delayed replica. At certain frequencies, the direct and delayed signals are of equal level and opposite polarity (180 degrees out of phase), and cancel out when combined.
PHONE PLUG: Cylindrical plug used with audio equipment, usually 1/4" in diameter. An unbalanced phone plug has a tip for the hot signal and a sleeve for the shield or ground. A balanced phone plug has a tip for the hot signal, a ring for the return signal, and a sleeve for the shield or ground.
PITCH: The subjective lowness or highness of a tone. The pitch of a tone usually correlates with the fundamental frequency.
PLUG: A "male" connector that inserts into a jack ("female" connector).
POLARITY: Refers to the positive or negative direction of an electrical, acoustical or magnetic force. Two identical signals which are in opposite polarity are 180 degrees out of phase with each other at all frequencies.
POLE PIECE: Metal pole attached to the magnet structure in a speaker's motor assembly that is surrounded by the voice coil, forming the inside wall of the gap.
PORT: Vent or tube tuned to extend the usable response of a woofer in an enclosure. The main difference between front- and rear-ported enclosures involves the way that each design disperses sound and colors certain parts of the sound spectrum. Rear-ported enclosures rely more on the acoustic environment; the sound changes depending on the distance from reflective surfaces. Front-ported enclosures tend to focus energy directly from the front baffle.
POTENTIOMETER: Variable resistor used to attenuate a signal.
POWER AMPLIFIER: Electronic device that increases the power level fed into it to a level sufficient to drive a loudspeaker. SWR power amps are most often used as the power section of a modular/rack system, in conjunction with a preamp stage.
POWER RATING: DC power available at the output terminals of a power source based on the manufacturer's specifications.
PREAMPLIFIER: More commonly "preamp." A device that, in the first stage of amplification in an audio system, boosts an instrument or mic-level signal to line level.
RACK: A 19"-wide wooden or metal cabinet that holds audio equipment.
RADIO-FREQUENCY INTERFERENCE: Or "RFI." The presence of radio-frequency electromagnetic waves in an audio component. It causes various noises in the audio signal.
RATED OUTPUT CURRENT: Maximum load current that a power supply can provide under specified operating conditions.
Re: Designation for the DC resistance of a speaker voice coil.
REFLECTED SOUND: Sound waves that reach the listener after being reflected by one or more surfaces.
RESISTANCE: Opposition of a circuit to the flow of current. Resistance, abbreviated "R," is measured in ohms and is calculated by dividing the voltage by the current.
RESISTOR: An electronic component that opposes current flow.
RESONANT FREQUENCY: The natural frequency at which a circuit oscillates or a device vibrates.
ROLL-OFF: The attenuation of frequencies above or below a certain point.
ROOT MEAN SQUARE (RMS) VALUE: Method used to calculate continuous average power output of an amplifier. For periodic function, it's the square root of the average of the square of the value of the function taken throughout one period (IEEE Std 100-1988). For a sine wave, it's peak value multiplied by 0.707.
SAFETY COMPLIANCE: Certification, recognition or approval by safety agencies such as Underwriters Laboratories Inc. (U.S.A.) and the Canadian Standards Association (CSA), etc.
SAFETY GROUND: Conductive path to earth that is designed to protect people from electrical shock by shunting dangerous currents that might occur due to malfunction or accident.
SENSITIVITY: Sound-pressure level that a loudspeaker produces at one meter when driven with one watt of pink noise.
SERIES WIRING: Circuit in which components are wired sequentially, dividing the voltage between them.
SERIES/PARALLEL: Circuit in which there are components wired in series and in parallel, often used in multi-woofer systems to optimize the impedance seen by an amplifier.
SHELVING EQUALIZER: Applies a constant boost or cut above or below a certain frequency so that the shape of the frequency response resembles a shelf.
SHIELD: Conductive enclosure, usually metallic, around one or more signal conductors used to keep out electrostatic fields that can cause hum or buzz.
SHORT CIRCUIT: An alternate path created between the positive and negative portions of a circuit, bypassing some or all components of the circuit and preventing operation.
SIGNAL: Varying electrical voltage that represents information, such as a sound.
SIGNAL PATH: Route that a signal travels from input to output in a piece of audio equipment.
SIGNAL PROCESSOR: Device that intentionally alters a signal in a controlled way.
SIGNAL-TO-NOISE RATIO: Ratio in decibels between signal voltage and noise voltage. An audio component with a high signal-to-noise ratio has little background noise accompanying the signal; a component with a low signal-to-noise-ratio is noisy.
SLAVE: Power supply using the reference in another power supply, the "master."
SLEWING RATE: Maximum rate of change a power supply output can produce when subjected to a large step response or specified step change.
SOUND: Longitudunal vibrations in a medium in the frequency range of 20Hz to 20,000Hz (that is, perceptible by the human ear).
SOUND-PRESSURE LEVEL: Or "SPL." Acoustic pressure of a sound wave, measured in decibels, above the threshold of hearing. Readings are often "weighted" to accomodate the nature of human hearing.
SOUND WAVES: Periodic variations in sound pressure radiating from a sound source.
SPEAKON CONNECTOR: Locking jack design that prevents accidental disconnection and offers a greater and more stable connection surface. It provides a more effective power transfer from amplifier to loudspeakers (especially from higher-powered amplifiers).
SPECTRUM: Output vs. frequency of a sound source, including fundamental frequency and overtones.
SPIDER: Speaker part attached to the junction of the cone and voice coil that keeps the voice coil aligned in the gap and helps suspend the cone.
STANDING WAVE: Apparently stationary waveform created by multiple reflections among opposing room surfaces. At certain points along a standing wave, direct and reflected waves cancel each other; at other points, the waves combine or reinforce each other.
STEREO, STEREOPHONIC: Audio recording or reproduction system with correlated information between two channels, and meant to be heard over two or more loudspeakers to give the illusion of sound-source localization (depth).
SUBWAVE™: An effect feature found on many SWR products. When engaged, the Subwave produces a signal one octave lower than the note being played.
SUBWOOFER: Speaker or speaker/enclosure system designed to reproduce only bass frequencies. Generally used only below 80Hz.
SWR: Manufacturer of the finest bass systems in the world; initials of company founder Steve W. Rabe.
THERMAL PROTECTION: Feature that shuts down a power supply if its internal temperature exceeds a predetermined limit.
THRESHOLD: Input level in a compressor or limiter above which compression or limiting takes place.
TRANSFORMER: Electronic component containing two magnetically coupled coils of wire. An input signal is transferred magnetically to the output, without a direct connection between the input and output.
TRANSIENT: Relatively high-amplitude and rapidly decaying peak signal level.
TWEETER: High-frequency loudspeaker.
UNBALANCED LINE: Audio cable with one conductor surrounded by a shield that carries the return signal. The shield is at ground potential.
UNDERWRITER LABORATORIES INC.: More commonly "UL." U.S. regulatory association chartered to test and evaluate products, including power sources.
VOICE COIL: Coil of wire attached to the rear of a speaker cone that works with the magnet to provide a motor to drive the speaker. The hook-up wires for a speaker connect the head unit or amplifier output to the voice coil.
VOLT: Basic unit of measurement for electrical pressure in a circuit.
VOLTAGE: Electrical pressure that can do work.
VOLTAGE REGULATION: Process of holding output voltage constant against changes in input voltage and load current, expressed as a percentage.
VOLUME: Number of cubic feet, cubic inches or liters of space in a speaker enclosure.
VOLT-OHM METER: Or "VOM." Analog meter that reads voltage, ohms and milliamperes.
WARM-UP TIME: Period, after turn-on, needed for a power supply to meet its performance specifications.
WARM-UP: Process of approaching thermal equilibrium after turn-on.
WATT: Unit of measure of power equal to one joule per second (W=El). Abbreviated "W" or "w."
WATTAGE: Electrical power amount designation.
WAVEFORM: Graph of sound pressure (or voltage) vs. signal time. The waveform of pure tone is a sine wave.
WOOFER: Low-frequency loudspeaker.
XLR CONNECTOR: Three-pin professional audio connector.
Z: Designation for a driver's nominal impedance.