A - B - C - D - E - F - G - H - I
L - M -O - P - Q - R - S - T
V - W - Y--Z
A test of some aspect of performance between two components. For example, a test of ambient noise between two different amplifiers can be compared. For the test to be scientifically valid, the input levels should be matched.
A device that randomly selects between two components for subjective testing. The listener doesn't know which device is being listened to. A high consistency of responses is regarded as significant.
Acronym for Alternating Current. An electrical current that reverses direction, alternating between positive and negative at a constant frequency- in the US, 60 hertz or cycles per second. The rate of change is measured in cycles per second, or hertz (hz). The majority of consumer electronics products --although they plug into the wall and receive alternating current--operate in a direct current environment, necessitating the inclusion of a transformer power supply to perform AC to DC conversion.
Acronym for Audio Codec-3. "Perceptual Coding" data reduction system developed by Dolby Laboratories to deliver 6 discrete audio channels (Left, Center, Right, Left Surround, Right Surround, and Low Frequency Effects) in a theater environment. See, Dolby Digital Surround Sound.
An electronic circuit that divides a line level audio signal into two or more frequency bandwidths and routes each to their appropriate amplifier.
Active or Powered Subwoofer
A subwoofer system that includes a built in amplifier(s).
Electronic circuit that converts an analog audio signal which varies in amplitude, into a digital signal, read as a numeric code created by series of pulses.
Acronym for Amplitude Modulation, a process that modifys the amplitude of a carrier wave in accordance with variations to the input voltage of the signal. This form of transmission is used in radio broadcast bands between 530 and 1750 kilohertz. Because it is subject to noise, interference, and restricted frequency response, it is not considered a high fidelity medium.
The acoustic characteristics of a space with regard to reverberation or sound reflection. A room with a lot of reverb is said to be "live"; one without much reverb is "dead."
Measurement of the strength of a signal. Usually measured in volts or decibels.
A signal that varies in amplitude, and is not characterized by discrete pulses (digital). A representation of original wavwefroms. It is a form of transmission, that in audio, represents in electrical terms, an acoustical waveform.
It is generally accepted that humans on average can hear audio frequencies varying from 20hz to 20,000hz. As we age the sensitivity to higher frequencies in the scale of our audible range progressively declines after about age 18. Attendance at rock concerts and other high decibel environments will acclerate the process.
A person who enjoys reading obscure information like this.
A process that reduces the amplitude or gain of an input signal.
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Sometimes used to describe a speaker cabinet, a baffle increases low frequency response of a speaker by providing an acoustical seal to prevent air being pushed out by the front of the speaker from interacting with air of similar amplitude and frequency, but 180 degreees out of phase behind the speaker. This prevents cancellation.
Band Pass Filter
A circuit that permits a limited range (or band) of frequencies to pass through unattenuated.
The gradient, or difference between the highest and lowest frequencies being transmitted. A higher bandwidth permits more information to be included, or transmitted in the signal. See, "Full bandwidth"below.
The frame or metal portion of a speaker driver that supports the magnet and cone suspension system.
A speaker system that utilizes a port in its enclosure and regulates the emmision of rear pressure so as to support rather than conflict, with the front wave. This enhances low frequency response.
The use of multiple amplifiers, feeding different parts of a speaker system, as in separately amplified woofers, and midrange/tweeters. Could be built into the speaker design or accomplished with the use of external amplifiers and electronic crossovers.
1) A high frequency signal used with tape media to elevate its frequency response by energizing the magnetic media.
2) A term applied to the electrical, mechanical or magnetic force or voltage applied to a device to establish the reference for nominal operation.
Information that is presented as a numeric bitstream of ones and zero's. The language of digital media.
A speaker that radiates signals from the front and the back of the enclosure. Both signals are in phase to each other. Bi-polar speaker designs are sometimes utilized to create a diffuse rear channel in a Pro-Logic surround environment.
The process of combining two channels of a stereo amplifier to create a more powerful mono amplifier. This process involves changes in the electrical circuitry that divide a single input into positive and negative sections and amplifies each separately. It then recombiners them at the terminus of the process. This modification is unique to each amplifier, and should not be attempted without the manufacturer's instructions. Often used in car stereo applications. The output will often be at high impedance only. An option found less frequently in pro and consumer applications.
Listening term. Usually refers to overly intense high frequency energy
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Center Channel Speaker
The key component in a Pro-Logic or Dolby Digital Surround audio system. Key to reproducing dialogue, the output of a center channel speaker can constitute more than 60% of what is heard in a home theater system.
The chopping off of the peaks of analogue waveforms (plateau-ing, if you will) that occurs when a signal has more amplitude than a process can pass on. The amplifier then cuts off the tops and bottoms of the waveforms, producing in effect alternating DC instead of AC. Excess clipping can easily damage speaker drivers in an audio system.
1) Phrase utilized to designate a speaker or speaker enclosure that features two drivers aligned along the same axis.
2) A phrase use to describe an speaker system that by its design, construction elements, or component selection expands the balance of musical tones. Also refers to cables where a signal carrier is protected by an outer ground.
Listening term. Refers to how well integrated the phase and crossover response of the system is realized.
Listening term. A visual analog. A "colored" sound characteristic adds something not in the original sound. The coloration may or may not be euphonically pleasant, but it is not as accurate as the original signal.
A cabinet enclosure that incorporates two woofers acting in tandem or mounted facing each other, facing away from each other, or even facing behind another.
A transducer (speaker) design that efficiently communicates radiated sound to a listening area. Sound is more restricted in coverage as frequency rises, so use in woofers and midranges is preferred.
An electronic (and sometimes passive) circuit that divides frequencies and routes them to their appropriate amplifiers (electronic crossover ) or speakers (passive crossover).
Undesirable leakage signal from one channel to another usually resulting in interference, or noise in the signal.
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Acronym for digital to analog convertor. Converts binary pulse information into audible analog signals that vary in amplitude. Commonly used in many kinds of digital media - CD's DVD's, digital satellite and cable transmissions.
The physical process of controlling resonance; or how well an amplifier controls speaker cone resonance after a signal is reproduced. Speakers may be electronically or physically dampened. Works by applying a countervailing signal to prevent the cone from moving after a hgh level signal is applied.
db - Decibel
Acronym for decibel, a logarithmic measure of sound. For every 3 decibels of audio gain, (the average sound differential a human can perceive) the wattage of an amplifier is doubled. An increase of 10 db is perceived as being twice as loud.
Direct Current: An electrical current that flows in one direction.
A speaker that radiates signals from the front and the back. Both signals are out of phase to the other. A Di-polar design is often utilized to enhance dispersion and create additional ambients in the signal.
Dolby Digital Surround Sound
Selected as the main audio system for DVD and Advanced Television, Dolby Digital Surround Sound is a data reduction process utilizing "perceptual coding" to compress up to 6 discrete streams of audio information into a data rate of 384 kilobits per second in the Theater environment or 448 kilobits per second in consumer applications (DVD/ATV). Perceptual Coding operates on the premise of reducing redundant data during the encoding process, masking noise and eliminating non-perceptual elements of the audio signal entirely.
Dolby Digital Surround is characterized by 5 full frequency (20 to 20khz) discrete channels ((Left, Center, Right, Left Surround, Right Surround)) of information. A discrete center channel localizes all dialogue entirely in this speaker with no bleed over in Left, Right or Surround channels. The discrete nature of all 5 channels allows audio images to be panned across the front, across the back, along each side, diagonally and full circle. Further, because the center channel is full range, music and sound effects may be panned across the front soundstage without frequency deviation as the image passes from Left to Center and Right. An additional low bandwidth channel of information in the datastream (the .1 in the 5.1) is dedicated entirely by the Foley artists to reproducing Low Frequency Effects (20 to 120hz) which add a greater dynamic to the audio experience.
Dolby Pro-Logic Surround Sound
Four channel surround sound process (Left/Center/Right and Surround). These four images are mixed into the Left Total and Right Total signals during encoding, permitting ProLogic signals to be embedded in, and ultimately read from a standard Left and Right channel stereo soundtrack. This process of encoding four channels into two carriers, (Left and Right) and retrieving them as 4 channels on the decode side is referred to as 4-2-4. The defining element of ProLogic is that it utilizes active decoders to localize dominant audio tracks (to position them correctly within the 360 degree sound stage in accordance to their proper established amplitudes) through the use of a high separation decoder processing. Frequency response of the rear channels is limited to 100hz to 7,000hz to eliminate crosstalk and sibilance errors between the center channel and rear surround. Low frequency non-directional signals (20-120) are generally routed to a subwoofer for reproduction.
Rather than measure absolute gain values to determine soundtrack dominance, Dolby Pro-Logic detects the differences in levels between signals to establish location and direction of dominant signals. The advantage of ProLogic is that it continuously monitors the signal to identify dominant as well as ambient components of the soundtrack. Enhancement and localization of dominant signals therefore is in proportion to their gain over embedded ambient tones. In some instance, enhancement will be large and powerful, more often, it is continuous and subtle.
Dome Tweeter or Midrange
A driver that has a dome shaped radiator. This is very effective with higher frequencies, in dispersing sound over a wide area, and is very popular. Domes can be of soft or hard materials to produce slightly different characteristics Other alternatives are cone and ribbon drivers.
A synonym for a transducer such as a woofer, midrange, tweeter, etc.
Acronym for Digital Signal Processing. Manipulation of an electronic signal using reverberation or delay lines and equalization to replicate ambient acoustics of a variety of audio environments. (Theater, Stadium, Night Club, etc.).
Positioned as a competitor to Dolby Digital, DTS audio is delivered in a theatrical environment as 5.1 channel Compact Disc that is synchronized to the film. In the home environment, DTS utilizes a compression scheme that insignificantly more bit hungry than its Dolby AC-3 counterpart. (1.2 megabits per second versus 448kbs for Dolby Digital) Proponents of DTS claim that the higher bit rate provides a smoother, sonically balanced audio performance. Like AC-3, DTS requires a dedicated processor to decode the compressed datastrea.
The ability of an audio device to respond to musical peaks. For example, an amplifier may only be capable of a sustained 100 watts, but may be able to achieve peaks of 200 watts for the fraction of a second required for an intense, quick sound. In this example the dynamic headroom would equal 3 db.
A measure in decibels (db) of the bandwidth, or difference between the loudest and the quietest passages in music. A wide dynamic range is preferable, as it more closely approximates the original production.
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A measure expressed in relative dB (decibels) of a speakers total output power contrasted against its input power in RMS watts. Comparative measurements are taken using 1 kilohertz, at one watt RMS, from 1 meter.
A speaker cabinet or box designed to create a proper resonance cavity to compliment the charateristics of a woofer.
A process that selectively adjusts the gain of frequencies in the audio signal. An equalizer is often utilized to compensate for deficiencies in room acoustics or the lack of speaker efficiencies.
A speaker that radiates sound from a large diaphragm that is suspended between high-voltage grids.
Pleasing. As a descriptive audio term, usually refers to a coloration or inaccuracy that non-the-less may be sonically pleasing.
How extended a range of frequencies the device can reproduce accurately. Bass extension refers to how low a frequency tone will the system reproduce, high-frequency extension refers to how high in frequency will the system play.
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Our sensitivity to sound depends on its frequency and volume. Human ears are most sensitive to sounds in the midrange at around 1000 Hz. At lower volume levels, humans are less sensitive to sounds outside the midrange; bass and treble sounds produced with the same intensity, are perceived to be at lower listening levels.
Acronym for Frequency Modulation, the shorter range transmission system (88 megahertz to 108 megahertz) utilized for audio and video. Less susceptible to interference than A.M.
Virtually all audio effects in a movie are created on a special soundstage (referred to as a Foley Stage), and not during actual filming of the scene. Punches landing, footsteps, bones breaking, car crashes, gunshots....all of these sounds are created in studio by a Foley artist utilizing a variety of sometimes unorthodox tools. The sound that you hear in a movie of bones breaking may actually be a crisp stalk of celery being snapped. The dinosaurs grunts in Jurassic Park are actually a mixture of the sounds of a variety of animals.
A measurement of the number of oscillations of an electromagnetic wave, expressed in cycles per second, or hertz (hz) A 60 cycle frequency signal is characterized by a wave that oscillates 60 times per second.
Expressed in hertz (hz) this is the measurement of the specific frequency bandwidth that a transducer is capable of recreating. Frequency response often includes a measure of db performance, ( plus or minus 3db) an indicator of how evenly, or flat the audible range is reproduced. the default average for humans is 20 to 20,000 hz.
Click Here to find this in the F Section of our Car Audio Glossary.
Bandwidth is the range of electronic signal frequencies a particular component can reproduce. For audio components like receivers, "full bandwidth" is generally considered to be the entire frequency range of human hearing: 20 to 20,000 hertz.
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A measure of signal amplification (loudness) that is expressed in decibels (db).
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A sound wave that is a multiple of the original frequency. ie: a 4khz signal is the first harmonic of a 2khz frequency.
A device for dissipating heat from a transistor or amplifier.
The output level that allows peaks in the signal to exceeds an amplifier's continuous operating rating momentarily without overloading or distorting.
The human ear is less sensitive at low frequencies than in the midrange. Reducing volume will cause the listener to notice how the bass seems to"disappear". To hear low bass requires an adequate SPL level. To hear 25Hz requires a much higher SPL level than to hear 250Hz. In the REAL world, low frequency sounds are reproduced by large objects; bass drums, string bass, concert grand pianos, etc. Listen to the exhaust rumble of a 454 cubic inch V8 engine vs. the whine of the little four banger. The growl of a lion vs. the meow of your favorite kitty. As frequency decreases we perceive more by feel than actual hearing and we lose our ability to hear exact pitch.
A measurement standard that is equal to the one cycle per second. One hertz is one cycle per second. 120 hertz is 120 cycles per second.
High Pass Filter
A circuit that allows only signals with frequencies above a predetermined level to pass through it.
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The extent to which speakers can accurately locate, or place instruments or vocals to, in effect create a soundfield in the room that is identical to the original recording.
Expressed in ohms, impedance represents the resistance to the flow of current in the signal. Impedance includes resistance from any source, including electrical capacitance and inductance and mechanical factors. Low impedance is desirable for signal interfaces as it is more efficient and results in a more accurate, noise free image.
Two or more signals that have the same waveform and identical amplitude in synchronization.
Integrated A/V Receiver
An audio component that combines pre-amplifier elements (multiple inputs, built in tuners, equalization, source switching) and amplifiers in a single unit.
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Any signal at .5 to 8 volts AC from an input device that requires amplification before it is sent to a speaker. Such signals are commonly exchanged among many types of audio interfaces.
A measure of the flatness of frequency response of a signal, as an indicator of the accuracy of the signal being reproduced.
Low Frequency Effects Channel
The .1 of a Dolby Digital 5.1 channel system. This is a stream of audio information that is limited in its frequency response (20-120hz) and is dedicated solely for the reproduction of low frequency special effects in the film.
Low Frequency Effects Woofer
The Low Frequency woofer in a Dolby Digital Surround system is designed specifically to reproduce 1 octave (20-120hz) bandwidth signals. Adds dramatic impact to car crashes, gun shots, explosions etc.
Low Frequency Extension
Manufacturers, writers and salespeople toss around all kinds of numbers and terminology that can be very confusing and misleading. "This $300 shoebox sized sub is flat to 20Hz" . Right, in your dreams . . . How is that cheap, tiny box and driver going to reproduce a 56 foot wavelength with enough power to be heard? It will not to it . Good bass reproduction requires moving a lot of air and playback at realistic volumes. Remember the rule of needing to move four times the air to go down one octave. Example: You have a pair of good quality tower speakers with 10" woofers that produce good bass down to around 40Hz. The salesman is telling you that his little subwoofer with a single 10" woofer will extend your system down to 20Hz. If you've been paying attention, you know that his woofer will have to move eight times as much air as each of your 10" woofers, not likely. Adding that subwoofer to your system mightgive you more apparent bass energy, and in fact may help a little with movie special effects, but it is unlikely to extend bass response significantly.
Low Pass Filter
A circuit that allows only signals with frequencies below a predetermined level to pass through it.
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Any speaker within two feet of a TV screen should include magnetic shielding to prevent color interference.
A process by which multiple signals are added, or encoded into the Left or Right signals through a process of adding or subtracting channel signals. This is the process that converts 4 channel Dolby Surround (Left, Center, Right and Surround) signals into 2 channels (Left, Right) of information.
The process of re-formatting audio or video signals onto and into information carrying (generally FM frequency for video and home theater audio products) signals. This is the method by which audio and video is transmitted and/or recorded.
To greatly decrease the volume level. Many receivers and pre-amplifiers have a muting control which allows the volume level to be cut way down without changing the master volume control. Great for when the phone rings.
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The unit of measurement for impedance, or resistance to the flow of electrical current.
Two or more signals that have the same waveform and share opposing amplitude values at the same time. Like waves crashing on to the shore meeting waves proceeding from the shore, out of phase signals that share the same temporal identity can cancel each other out.
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A transducer (speaker) in a cabinet that relies on pressure generated within the cabinet to reproduce low frequency signals. When done well, it reinforces the bass wave. A speaker that is not connected to an amplifier, but accompanies another in the cabinet that is connected to an amplifier.
A subwoofer that does not incorporate a built in amplifier, and therefore requires external amplification.
Pulse Code Modulation. A means of digital encoding.
The basis for Dolby Digital data reduction, the fundamental concept behind Perceptual audio coding is to emphasize sounds that we do hear in a signal and to strip away sounds that we do not hear, and by doing so, take advantage of a limited amount of spectrum (384 kilobits per second in a theater and 448 kilobits per second in DVD) to deliver multi-channel audio information in a digital environment. Perceptual Coding employs a Data reduction scheme that makes use of auditory masking and distribution of bits along narrow frequency bands to match the requirements of reproducing the frequency range and dynamic range of the coded audio . Channels that have higher frequency content are allocated more bits in this codec; simultaneously this process allows higher gain sounds that occur in one channel to provide for the masking of noise in another channel.
A flat panel speaker.
A synthetic material utilized in speaker cones. Characterized by light weight, low resistance and minimum resonance, Polypropylene speakers offer the enhanced elasticity necessary to reproduce fast transient signals.
An opening in the speaker cabinet that allows the cabinet to "exhale" low frequencies generated off the back of the speaker, extending bass response. A ported cabinet generally allows higher power handling, higher speaker efficiencies and improved low frequency performance. This function may also be performed by a passive radiator (see above).
Most multi-unit loudspeakers try to approximate a point-source. Think of a pebble dropped into the water and the expanding wave pattern away from impact. Obviously it is difficult to integrate multiple point-sources into a truly coherent expanding wave. The best designs do quite well with careful driver engineering and crossover development.
The second stage of an integrated A/V receiver or a separate unit. Amplifies low level signals received from the pre-amplifier.
Or Pre-amp is a device that takes a source signal, such as from a turntable, tape-deck or CD player, and passes this signal on to a power-amplifier(s). The pre-amp may have a number of controls such as source selector switches, balance, volume and possibly tone-controls. Magnetic phono cartridges always require equalization preamps.
Pulse Width Modulation - another method employed in diital amplifiers to shape sonic response.
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Q or Quality Factor
A measure of damping. Modern home speaker systems have Q values ranging from < .5 to approx. 2.0. Q values < .7 have no peak in the response. Q values around .5 are considered to be optimally damped, having a Bessel response. A Q of 1.0 is a Butterworth response. The lower the Q value, the better the transient response of the system, (less or no ringing), but the tradeoff is a larger required box size and the response begins to rolloff at a higher frequency. Another way to consider it is that the lower the Q, the more gradual the rolloff but the rolloff begins at a higher frequency.
Click Here to find this in the Q Section of our Car Audio Glossary.
The conversion of an analogue signal into a binary word of digital information.
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An audio component that combines a pre-amplifier, amplifier(s) and tuner in one chassis. A Dolby Prologic Receiver also contains a Dolby Prologic decoder for surround sound.
Any system has a resonance at some particular frequency. At that frequency, even a slight amount of energy can cause the system to vibrate. A stretched piano string, when plucked, will vibrate for a while at a certain fundamental frequency. Plucked again, it will again vibrate at that same frequency. This is its natural or resonant frequency. While this is the basis of musical instruments, it is undesirable in music-reproducing instruments like audio equipment.
A reduction in the flow of electrical current related to the inability of a given conductor to carry it fully. All materials are electrically resistive to some extent.
The square root of the mean of the sum of the squares. Commonly used as the effective value in measuring a sine wave's electrical power. A standard in amplifier output power and speaker power handling measurements.
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A measurement of the number of times an analog waveform is sampled by digital words to create a rendering of same.
The ratio, expressed in decibels between a signal's output gain, and the accompanying noise contained within. A higher signal to noise ratio is desirable. A ratio over 80 dB is beyond the threshold of human perception.
The amount of input signal strength, or gain required by a tuner or amplifier to reproduce or achieve certain output levels. Expressed in microvolts, the lower the rating, the higher the sensitivity of the device.
Another use of this phrase is to describe the sound pressure levels (SPL) of a speaker at a pre-determined distance and input.
The measurement (in decibels) of the isolation between two signals. A signal with high separation will reproduce a far more accurate and realistic stereo image. In order to deliver a passable Dolby Surround matrix, a stereo signal must have at least 19db of separation.
Sound waves can be thought of like the waves in water. Frequency determines the length of the waves; amplitude or volume determines the height of the waves. At 20Hz, the wavelength is 56 feet long! These long waves give bass its penetrating ability, (why you can hear car boomers blocks away).
The conical surface of a common dynamic speaker (driver) that radiates sound.
Equal sonic pressure resulting in balance across the entire frequency spectrum of the audio range.
SPL (Sound Pressure Level)
A loudness scale relative to a standard input signal consumption of 1 watt measured in decibels (db). SPL of speakers is measured utilizing a 400hz tone one meter from the speaker along its front to center axis.
A low frequency driver designed to reproduce low frequency, non directional (20 to 120hz) signals in an audio system. As a separate unit, it may have its own dedicated amplifier.
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Acronym for Tomlinson Holman Experiment. Audio standard for surround sound system that utilizes de-correlation (use of selective phase and gain shifting) to approximate the audio tonalities of a large theater within a restricted spatial confines (and smaller speakers) of a home theater.
THX-certified speakers meet the quality-control criteria defined by Lucasfilm, the company formed by George Lucas — creator of the Star Wars and Indiana Jones movies. Today, there are more than 45 licensed manufacturers producing THX-certified components for home theater systems.
The quality of a sound that distinguishes it from other sounds of the same pitch and volume. The distinctive tone of an instrument or a singing voice.
Total Harmonic Distortion
Measurement of all of the distortion in a signal. Measured as a percentage of the overall signal.
A speaker, microphone, or phono cartridge. A device that converts energy or signals from one form to another.
The ability of a component to respond quickly and accuratly to transients, with minimal distortion. Transient response affects reproduction of the attack and decay characteristics of a sound.
Bursts of high energy or spikes of gain in an audio signal. Frequently in the low frequency range.
Triaxial (3-way) Driver.
Phrase utilized to designate a speaker or speaker enclosure that features three drivers aligned along the same axis.
Two Way Speaker System
A speaker that consists of two drivers ( woofer and tweeter) and a passive crossover network that enables each to reproduce a selected band of frequencies to maximize Linearity and frequency response of the cabinet.
A cone, dome, or horn audio transducer made to most efficiently produce the high end (4000 to 20,000 Hertz) of the audio spectrum.
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Click Here to find this in the V Section of our Car Audio Glossary.
The wire coil of a speaker that works in conjunction with the magnet to convert electrical signals into mechanical energy. The resulting movement of the speaker cone creates sound.
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A listening term. The opposite of cool or analytical. In terms of frequency, generally considered the range from approx. 150Hz-400Hz. A system with the "proper" warmth will sound natural within this range. This has also been a term used to describe in positive terms, the distortions and colorations associated with vacuum tubes.
The distance the sound wave travels to complete one cycle. The distance between one peak or crest of a sine wave and the next corresponding peak or crest. The wavelength of any frequency may be found by dividing the speed of sound by the frequency. (Speed of sound at sea level is 331.4 meters/second or 1087.42 feet/second).
A low frequency speaker associated with the production of signals from 20 to 150hz.
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Any type of connection that splits a signal into two parts. An example would be a connector with one male RCA plug on one end, and two female RCA jacks on the other end.
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