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Audio Glossary of Terms

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-A-

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Acoustic suspension
Acoustic suspension is a type of speaker enclosure that uses a sealed box to provide tight, accurate bass response. It gives up some efficiency to provide bass that is more accurate and controlled, so compared to a bass reflex design, it may require more amplifier power to play at the same volume level.

Active
Containing tubes or transistors that require an external source of power, and typically provide amplification.

Active Crossover
A powered electronic network that divides up the frequency constituents of an audio signal (bass, midrange, and treble) before it is amplified and sent to the various drivers in a speaker system. While active crossovers are often contained within sub-woofer enclosures along with the bass driver(s), those that work with multiway systems may also be outboard mounted.

Amp
Short for amplifier, and also the abbreviation of Ampere, the unit for electrical current. Electrical current is sent through the speaker input terminals to make the speaker produce sound. A good 120 watt amplifier can momentarily send a peak current of 80 amps through a speaker, which will really rattle your windows; maximum sustained average current at 120 watts, which is also very loud, is around 4 amps.

Amplifier
An amplifier is a device (sometimes called an "amp") for boosting the amplitude of a given electrical signal; ideally, without affecting its quality.

Analog Signal
The exact electrical or mechanical replica of any particular audio or video input to a system. Any signal originally produced by non-digital recording equipment, even though the finished item may be a digital audio disc or a digitally compressed video signal. Note that no matter what the recording medium, the sound or picture we ultimately experience is analog. We live in a subjectively analog world.

Audiophile
A person who has an enduring interest in audio.

 

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Bandwidth
A Range of frequencies. With audio recordings,bandwidth refers to the sound system's or recording's ability to capture the frequency-response range of the ensemble and soloists. With regard to a home playback system, it refers to the "audible" bandwidth the system should be able to reproduce, usually from 20 or 30 Hz up to 15 or 20 kHz.

Bass
The low-frequency range of the audible spectrum, running from 20 Hz (or a bit lower) up to anywhere from 200 to 500 Hz, a total of four octaves or more.

Bass reflex
A type of speaker enclosure that includes a "tuned" port or passive radiator to increase and extend bass response (by releasing some of the energy created by the inward movement of the woofer cone). Bass reflex designs are more power-efficient than acoustic suspension designs — they'll play louder than an acoustic suspension speaker when driven with the same amplifier power. But they may sacrifice some bass accuracy in exchange for the added bass output.

Bi-Wiring
A method of connecting an amplifier or receiver to a speaker in which separate wires are run between the amp and the woofer and the amp and the tweeter. This can only be done when the loudspeaker has apassive parallel crossover ;if the crossover is of the series type, which offers significant advantages, the loudspeaker cannot be bi-wired.

 

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Capacitor
A component in crossover networks. Available at electronic supply stores. Capacitance is denominated in Farads. A cousin of a resistor, but presents a high resistance to low frequencies, and low resistance to high frequencies. Perversely, more capacitance means less resistance.

CEDIA
Custom Electronic Design and Installation Association. A national dealer organization that requires its members to have at least two years experience and be licensed and insured. While not exactly a degree in home audio-video, CEDIA certification at least means that a dealer has some basic knowledge about audio and video. However, I have seen installations by CEDIA members that were much less effective than they could have been, probably because the customer was more interested in visual aesthetics than performance.

Center Channel
The center speaker in a home theater setup is somewhat considered the dialogue speaker and is ideally placed within one or two feet above or below the horizontal plane of the left and right speakers, and above or below the television. Important part of the surround sound set-up and usually the odd speaker ie..5.1 system refers to 4 speakers with one center-channel speaker being the 5th and the point one referring to the powered sub-woofer.

Channel
In audio, a distinct path for a signal that is being recorded or played back. Standard stereo has two channels. Pro Logic-decoded audio still has two, but they carry two additional "matrixed" channels. Dolby Digital and DTS audio have five full-range channels and a subwoofer channel. In video, a signal transmitted at a particular frequency.

Clipping
In audio, the result of an analog signal's being overdriven to the extent that its peak levels cannot be accommodated, and therefore are "clipped" off from the audible signal. Typical in smaller amplifiers, it is the most audible of common electronic distortions.

Coloration
In audio, a subjective term to describe levels of audible distortion.

Cone
The cone-shaped part of a loudspeaker driver that moves the air. Made of paper, polypropylene, or recently out of high-tech materials such as Kevlar and glass fiber.

Connectors
There are several different ways to connect the cables from your receiver or amplifier to your speakers. Bare wire connections are acceptable, especially with "spring clip" terminals. Other popular connectors are Banana plugs will plug straight into the center of 5-way binding posts. They make a quick and convenient connection. The Double-banana plug which is the same as banana plugs, except the positive and negative banana connectors are both fixed in a molded housing that spaces them 3/4" apart. Pin Connectors will work with both spring clip and binding post terminals. This is probably the best type for connecting a thick, heavy-gauge wire (16gauge) to a small spring clip connector. On a 5-way binding post, this slender pin will also fit the hole that's back near the base of the central post.

Crossover
A component that divides an audio signal into two or more ranges by frequency, sending, for example, low frequencies to one output and high frequencies to another, you might say it works as a filter, allowing certain frequencies to pass through to the speaker while blocking others. . An active crossover is powered and divides the line-level audio signal prior to amplification. A passive crossover uses no external power supply and may be used either at line level or, more commonly, at speaker level to divide the signal after amplification and send the low frequencies to the woofer and the high frequencies to the tweeter, thus the term 2-way or 3-way speaker.

 

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Decibel (dB)
The standard unit of measure for expressing relative power or amplitude differences. with audio, it represents loudness. One dB is the smallest change in loudness most people can detect. A 1 dB difference is barely noticeable, but a 10 dB difference is big — a speaker playing at 10 dB higher volume will sound roughly twice as loud. A 3dB difference equates to a doubling of power.

Diaphragm
The part of a speaker driver that moves, producing the sound. Each diaphragm is directly connected to a voice coil. The diaphragm for a woofer is a cone, while for a tweeter, it's often a dome.

Diffusion
The scattering of sound. Diffusion reduces the ability of a listener to pinpoint the actual location of a speaker, a useful quality in surround speakers. Diffuse surrounds create a wraparound soundfield that draws you into the on-screen action.

Dipole
A speaker design that uses two sets of drivers to generate equal amounts of sound both forward and backward, or side to side, with the two sounds being "out of phase.” Dipoles are often used as surround speakers, and are very effective at creating a diffuse soundfield when placed on the sides of the listening position.

Direct and reflected sound
The sound that you hear from your listening/viewing position is a combination of the direct sound that travels straight from your speakers to your ears, and the indirect, reflected sound — the sound from your speakers that bounces off the walls, floor, ceiling or furniture before it reaches your ears.

Dispersion
The degree to which a speaker's sound is spread over the listening area.

Distortion
Distortion: falsified reproduction of an audio or video signal caused by change in the wave form of the original signal.

Dolby Digital
An encoding system that digitally compresses up to 5.1 discrete channels of audio (left front, center, right front, left surround, right surround, and LFE) into a single bitstream, which can be recorded onto a DVD, HDTV broadcast, or other form of digital media. A Dolby Digital processor (found in most receivers purchased after 2005) can decode this signal back into the 5.1 separate channels. Most films are recorded in a 5.1 digital format, though a number of films before 1992 had 6-channel analog tracks that have been remastered into 5.1.

Driver
Any individual diaphragm (cone, dome, etc.) within a speaker that compresses and rarefies the air to create sound waves, such as a woofer, tweeter, midrange, etc.

Dynamic range
The difference between loud and soft sounds. A speaker with wide dynamic range — one that can reproduce the sudden and wide changes between loud and soft sounds in music and video soundtracks — will sound more realistic (all other things being equal).

 

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Efficiency
The efficiency rating for a speaker is a measure of how well a speaker converts watts of electrical power into watts of acoustical power. Most speakers have a very low efficiency rating — between 1% and 10% — so manufacturers rarely provide this information, choosing instead to list sensitivity ratings.

Enclosure
The container of air that surrounds the rear of a speaker driver.

Equalizer
A component designed to alter the frequency balance of an audio signal. Equalizers may be graphic, parametric, or a combination of both.

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Feedback
The transmission of current or voltage from the output of a device back to the input, where it interacts with the input signal to modify operation of the device. Feedback is positive when it's in phase with the input and negative when it's out of phase.

Flat
When a speaker's response is described as "flat," that's a good thing. It means that the speaker can accurately reproduce a signal that is fed to it without adding unnatural coloration to the sound. Specific frequencies don't sound too loud or too soft.

Frequency response
The human ear responds to frequencies from approximately 20 to 20,000 cycles-per-second, or Hertz. A speaker's frequency response indicates how much of that range can be reproduced.

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Gauge
American wire gauge(AWG), also known as the Brown & Sharpe wire gauge, is a standardized wire gauge system used since 1857 predominantly in the US for the diameters of round, solid, nonferrous, electrically conducting wire. The cross-sectional are of each gauge is an important factor for determining its current-carrying capacity. Music gauge is generally thinner than steel gauged wire. The lower the number of gauge, typically the thicker the wire and the further distance the current can travel.

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Hertz (Hz)
The unit of sound frequency; one Hz is equal to one cycle per second. The range of human hearing is 20-20,000 Hz. Points of reference: low "E" on a bass guitar is 41 Hz; middle "C" on a piano is 262 Hz; cymbals can go out to 15,000 Hz.

 

 

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Imaging
The ability of a speaker to reproduce spatial information in a recording so that you can visualize the relative positioning of individual voices and instruments as you're listening.

Impedance
The load value (in ohms) that the speakers present to the amplifier — the amount of resistance to the flow of current. While playing music, a speaker's actual impedance constantly fluctuates; however, speakers are usually given a single nominal impedance rating for easy comparison. Low-impedance speakers (4 ohms or less) can cause problems with receivers or amplifiers that are not designed to deliver large amounts of current.

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Kilohertz (kHz)
One thousand Hertz.

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LFE input
Found on some powered subwoofers, this special preamp-level input accepts the "Low Frequency Effects" signal that's output by digital 5.1-, 6.1-, or 7.1-channel home theater receivers, ensuring proper bass reproduction. This type of input doesn't route the signal through any processing inside the sub which could potentially interfere with the low-pass crossover built into the receiver's bass management circuitry. Some powered subs feature an unfiltered LFE input/output — the output sends full-range signals minus the low frequencies back to a receiver or preamplifier's "main in" jacks for even more precise sonic control.

Linearity
Linearity: having or being a response or output that is directly proportional to the input.

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Midrange
The middle of the audio frequency range. Also used as a term for loudspeaker drivers designed to reproduce this range.

MDF
Medium Density Fiberboard or MDF is a composite wood product similar to particleboard. It's made out of wood waste fibers glued together with resin, heat, and pressure. MDF is appropriate for many applications, from cabinetry to moulding, because it is smooth, uniform, and won't warp, even in high humidity. It also known for being strong and easy to shape.

Motor structure
The part of the speaker that moves a diaphragm to produce sound. The motor structure basically consists of a voice coil that sits inside a cylindrical magnet. Alternating current is pumped through the voice coil, which constantly changes its magnetic polarity. As the voice coil alternates between being attracted to and repelled by the magnet, it moves the attached driver to create sound.

 

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Neodymium
A material used in some speaker magnets. Neodymium magnets are smaller and more powerful than conventional speaker magnets.

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Octave
The difference between two frequencies where one is twice the other. For example, 200 Hz is an octave higher than 100 Hz. 400 Hz is one octave higher than 200 hz.

Ohm
A measure of how much something resists (impedes) the flow of electricity. Larger numbers mean more resistance.

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Passive
Not active. A passive crossover uses no external power and results in insertion loss. A passive speaker is one without internal amplification.

Passive Radiator
A radiating surface (usually similar to a conventional speaker cone) that is not electrically driven but shares the same air space in a sealed cabinet with an electrically driven loudspeaker. This arrangement is functionally similar to a loudspeaker with a vented (ported) cabinet, with the passive radiator serving the duties of the air in the port

Piezo
A type of speaker driver that creates sound when a quartz crystal receives electrical energy.

Phase
Refers to the timing relationship of two or more signals or sound waves. It's especially important to be sure that your stereo speakers are playing "in phase." This means that the drivers (woofers and tweeters) of your right and left speakers are moving in and out at the same time. If your stereo speakers are "out of phase" — that is, with one set of positive and negative leads reversed — you'll hear significantly less bass, and instead of producing a strong center image, the sound tends to stay localized at the speakers.

Phase control
A 2-position switch found on some powered subwoofers that lets you delay the subwoofer's output slightly so that it is in phase with the output from your main speakers.

Port
An aperture in a loudspeaker enclosure that helps extend the usable low-frequency output. A ported enclosure is also called vented or bass reflex.

Power handling
A measure of how much amplifier power, in watts, a speaker can take before it is damaged.

PVC
polyvinyl chloride: a polymer of vinyl chloride used instead of rubber in electric cables, can endure weatherization and extreme condition

 

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RCA
A plug and socket for a coaxial cable that is widely used to connect audio and video components. They are found on every TV, DVD player, stereo amplifier, set-top box and countless other devices. Comprising two wires; an inner signal and an outer ground, RCA connectors are also known as "phono connectors." In the 1940s, RCA (Radio Corporation of America) designed them to cable a "phonograph" turntable to an amplifier (mono, not stereo).

Receiver
Any component that receives, or tunes, broadcast signals, be it NTSC, HDTV, DBS, or AM/FM radio. Typically refers to the single component that includes a preamp, surround processor, multichannel amplifier, and AM/FM tuner.

Resonance
When a component or system vibrates more at a certain frequency than at any other frequency. In a speaker system, resonance with the speaker enclosure or any of the components can lead to colorations in the sound.

RMS
A term used to indicate the average level of power that a receiver or amplifier can sustain over a given period of time. Average power ratings (ex: 100 watts RMS) provide a more realistic assessment of your amp's performance than peak power (ex: 400 watts peak/dynamic power) since an amp can only sustain peak power for a short period of time. (RMS stands for "root mean square," which is one of the mathematical methods used to calculate an amp's average power output, and is commonly used throughout the industry to represent the average power rating.)

ROHS
Restriction of Hazardous Substances Directive (RoHS), adopted in February 2003 by the European Union, is intended to reduce the effect of hazardous waste created by electronic products on the environment. The directive took effect on July 1st, 2006, and places clear restrictions on the use of six hazardous materials used in the manufacture of electronic and electrical components.

 

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Satellite speaker
A small speaker with limited bass response that's often designed to be used with a matching subwoofer.

Sensitivity
A measurement (in dB) of the sound-pressure level over a specified frequency range created by a speaker driven by 1 watt (2.83V at 8 ohms) of power with a microphone placed 1 meter away. Essentially, the higher the rating, the louder your speakers will play with a given amount of amplifier power. For Example: If a speaker has a sensitivity rating of 85 dB it will require 100 watts to produce a given volume, at that same volume, if you have a speaker that has a greater dB such as, 88 dB it will only require 50 watts of power. Further, if you have a speaker that has a 91 dB sensitivity rating, to achieve the same level of volume it would only require 25 watts of power. A higher dB is ideal when considering multiple speakers off one receiver.

Soft-Dome Tweeter
A tweeter that uses a soft fabric or plastic dome as the radiating diaphragm.

Soundstaging
A stereo or home theater system's ability to present music, dialogue, and other sounds as taking place within a physical space with definite width, height, and depth. The individual vocal and instrumental "images" are part of the "soundstage."

Speakon
A connector used to connect amplifiers to speakers, generally used in pro audio systems. This connector has a twist lock feature, to ensure the connectivity of the cable.

Spider
Part of a loudspeaker driver's suspension that helps center the diaphragm and returns it to rest after being moved by an energized voice coil.

SPL (sound pressure level)
The intensity or volume level of sound (measured on the dB scale).

Subwoofer
A speaker designed to reproduce very low bass frequencies, usually those below about 80 Hz.A "powered subwoofer" includes a built-in amplifier to drive the speaker.

Surround
Connects a driver's diaphragm to its basket. The two most common surround materials are rubber and foam. Rubber typically lasts longer than foam, especially in warm, moist climates, but tends to cost more.

Surround speakers
In a home theater system, the speakers located beside or behind the listening/viewing position. These speakers can be mounted on the walls, in the wall or placed on stands, or set on bookshelves. They help create an enveloping three-dimensional soundstage by reproducing the surround information on video soundtracks and music recordings encoded with surround sound.

 

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Terminals
You probably don't think about the connectors on the back of your speakers until you go to hook them up. There are two basic types: spring clips and binding posts.

Spring clip terminals
Usually found on lower-priced speakers, and low- to medium-priced receivers. They work best with bare wire connections with small-gauge speaker wire, or pin-type connectors

Binding post terminals
Sturdier, more versatile type of speaker jack, often found on higher-quality speakers and receivers, and on most amplifiers. They're threaded, so you can tighten them down against the wire or connector for an extra-snug connection.

THX
Certification program for home theater equipment. Uses some proprietary features, but mostly assures a base quality level for a given room size. (See THX Select or Ultra.) Is compatible with any and all soundtrack formats. Stands for either Tom Holman's eXperiment, after the engineer who drafted the original standard, or is named after the company's founder George Lucas' first movie, THX 1138. Nobody agrees on which.

Timbre
Pronounced "tam-burr." The quality of a sound related to its harmonic structure. Timbre is what gives a voice or instrument its sonic signature — for instance, why a trumpet and a saxophone sound different when they play the same note.

Transducer
Any device that converts one form of energy into another form of energy, specifically when one of the quantities is electrical. Thus, a loudspeaker converts electrical impulses into sound (mechanical impulses), a microphone converts sound into electrical impulses, a solar cell converts light into electricity, etc.

Transient
A short-lived aspect of a signal, such as the attack and decay of musical tones. A speaker that can react quickly to rapid changes in the music is said to have good "transient response."

Tweeter
Usually small and lightweight reproducing the highest musical frequencies, like violins, cymbals, female vocals, etc.. A tweeter is a loudspeaker designed to produce high frequencies, typically from around 2,000 hertz to 20,000 hertz (generally considered to be the upper limit of the human hearing). Nearly all tweeters are electrodynamic drivers, using a voice coil suspended with in a fixed magnetic field. These designs operate aby applying current from an amplifier to a coil. The electrified voice coil produces a varying magnetic field which works against the fixed magnetic field, forcing the voice coil – and the diaphragm attached to it – to move. Since the coil is attached to a diaphragm, its motions become those of the diaphragm creating air motions which we hear as high sounds.

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Video shielding
A way of containing a speaker's magnetic energy inside its enclosure. This is usually achieved by placing another speaker magnet back-to-back with the existing one so that the two magnetic fields cancel each other. Shielding may also be achieved by lining the inside of the speaker cabinet with metal. Video shielding is important for home theater speakers — especially the center channel speaker — because if an unshielded speaker is placed too close to your TV, the magnetic energy can cause picture distortion and even permanently damage the TV's picture tube.

Voice coil
The cylindrical coil of wire that moves in the magnetic field of a dynamic driver. The voice coil is bonded to the diaphragm, which actually produces the sound.

Voice-matching
When speakers possess a similar timbre or tonal quality. Voice-matched (or timbre-matched) speakers in a home theater system will result in more seamless, consistent, convincing wraparound sound. A good way to get voice-matched speakers is to stay within a family or series of speakers from a single manufacturer, or to get a pre-matched multi-speaker system.

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Watt
A unit of power or energy. One horsepower is equal to 745.7 watts.

Woofer
A type of driver that features a cone-shaped diaphragm, commonly used for producing the mid- and low-frequency portions of the music signal.

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Zone
One or more rooms powered by one or more amplifiers, which are all fed by one source. A home can be divided into multiple zones, which can play multiple sources, even though several rooms (say, the kitchen, dining room, and living room) all play the same source.