AC-3 (audio coding 3)- Dolby's digital audio data compression algorithm adopted for HDTV transmission and used in DVDs, laserdiscs and CDs for multichannel home theater use. Also see: Dolby Digital.

Acoustic Suspension- A sealed or closed box speaker enclosure. Sometimes incorrectly referred to as an infinite baffle. Also see: Sealed Enclosure.

Acoustic Treatments- There are only three classic (physical) tools available for the acoustician to treat a room: absorbers, reflectors and diffusers. Absorbers attenuate sound; reflectors redirect sound, and diffusers (hopefully) uniformly distribute sound. However, with today's advanced digital audio tools, all of these elements can be electronically manipulated.

Acoustics- The science or study of sound.

Active Crossover- A loudspeaker frequency divider requiring power to operate. Its outputs are fed into power amplifiers, with a 2-way crossover requiring 2 amps, a 3-way requiring 3 amps etc.

Alternating Current- (AC) An electrical current that periodically changes in magnitude and direction.

Ambience- The acoustic characteristics of a space determined by reverberation. A room with a lot of reverb is said to be "live"; one without much reverb is "dead."

Ambient Noise- The sound that exists in a room that does not come from a loudspeaker, musical instrument or some other intentional sound source. A person speaking to an audience is not ambient noise, etc.

American Wire Gauge- (AWG) - A system for measuring the thickness of wire. The lower the AWG number, the greater the thickness. Also see: Gauge.

Ampere (A or AMP)- The standard measure of electrical current flow. One amp is equal to one Coulomb of charge flowing past a point in one second.

Amplifier- A device which increases signal level. Many types of amplifiers are used in audio systems. Amplifiers typically increase voltage, current or both.

Amplitude- The peak-to-peak size of a waveform. For audio purposes, the greater the amplitude of the signal, the louder the sound will be.

Analog- A representation of sound waves that is continuous. In contrast, digital representations consist of values measured at discrete intervals.

Anamorphic- A process where a widescreen movie is stored on the DVD disc in anamorphic form, meaning the picture is squeezed horizontally to fit the standard 4:3 rectangle, then unsqueezed during playback. This anamorphic squeezing results in less of the picture being wasted on the black letterbox mattes. Anamorphic video is best displayed on widescreen equipment, which stretches the video back out to its original width. The setup options of DVD players allow the viewer to indicate whether they have a 16:9 or 4:3 TV.

Anechoic- Echo free. An anechoic room has no reflected sound. This is accomplished by treating all of the room's surfaces with sound absorbing material.

Aspect Ratio- Ratio of a picture's width to its height. Typical television aspect ratio is 4:3, while wide screen formats provide greater width of the viewing area.

Asymmetrical- Uneven or off center; not symmetrical. In speaker cabinet design asymmetry can be beneficial as it reduces the standing waves in the cabinet.

Attenuate- To reduce in level.

Audio frequency- The acoustic spectrum of human hearing, generally regarded to be between 20 Hz and 20 kHz.

Axis- For speakers, the imaginary line that runs from the speaker to the intended listener position.

Banana Plug- Banana shaped speaker termination that consists of an approximately 1/8-inch-wide and 1-inch-long plug that goes into the back of a binding post or inset banana plug terminal on a speaker, amp or receiver.

Bandwidth- A specific range of frequencies.

Basket- Part of a speaker, typically of cast metal, that holds together the driver, magnetic structure, voice coil, cone and spider.

Bass- (low frequencies) - The low end of the audio frequency spectrum between 0Hz to about 200 Hz.

Bass Reflex- A type of loudspeaker that uses a port or duct to augment the low-frequency response. Opinions vary widely over the " best" type of bass cabinet, but much has to do with how well a given design, such as a bass reflex is implemented. See also: Ported Enclosure.

Bi-amping- Bi-amping refers to the use of two separate amplifier channels connected directly to individual loudspeaker drivers. Bi- amping requires (usually) an external active crossover to separate the frequencies before sending them to the respective amps.

Binding Post- Speaker wire terminal on better amplifiers and loudspeakers; can accept multiple cable termination types. Superior to spring or wire-clip connectors. (See banana plug, pin connector, spade lug, spring clip)

Bipolar- Type of loudspeaker with drivers mounted on opposite sides of the cabinet, or speaker enclosure. Drivers move in and out together so they remain "in-phase." Often used as rear-surround speakers. Also see: Dipolar)

Biwiring- The use of two pairs of speaker wire from the same amplifier to separate bass and treble inputs on the speaker.

CATV- (community antenna television or cable television) A broadband transmission medium, most often using 75-ohm coaxial cable carrying many TV channels simultaneously.

CD- (compact disc) Trademark term for the Sony-Philips digital audio optical disc storage system. The system stores 75 minutes ( maximum) of digital audio

CD-R- (compact disc-recordable) A compact disc that is recordable once.

CD-RW- (compact disc-rewriteable) A compact disc that can be recorded on more than once.

Center Channel (Speaker)- The center channel speaker is used to produce the voices, dialogue, or any other sound effects the director mixes into it. In a home setting it is preferable to have the center channel speaker either directly on top of, or directly below, your television. It is important that the center channel is voice-matched to the front left and right speakers especially, if not also the rear left and right. This creates a seamless and convincing soundstage for movies.

Chrominance- Abbreviated C. The color portion of the video signal - includes hue and saturation information but not brightness Also see: Luminance.

Coax- Short for Coaxial cable - a type of 75 ohm cable most commonly used for Cable TV connections and with some antenna systems for FM radio and Television. Also used to connect CD or DVD transports to DACs. May also be found as the basis for many video interconnect cables including composite, s-video, component, and RGB.

Coherence- Listening term. Refers to how well integrated the sound of the system is.

Coloration- Listening term. A "colored" sound characteristic adds something not in the original sound. The coloration may be sonically pleasant, but it is not as accurate as the original signal.

Compact Disc Transport- Component which reads the binary information from a compact disc and sends this bitstream into an external device for analogue conversion. (Commonly used with a digital-to-analogue converter.)

Compliance- The relative looseness (inverse of stiffness) of a speaker suspension, specified as Cms.

Component Video- A video signal transfer method utilizing three cables which separate the three parts of a video signal: Luminance (Y) is the black & white, pR and PB are the separate portions of the Chrominance, or color signal. Component Video, properly implemented, should provide the best possible image quality on TV monitors that support it.

Composite Video- A video signal combining luminance, chrominance, and synchronization data on a single coax cable using RCA connectors. It is typically color-coded yellow.

Cone- The conical diaphragm of a speaker attached to the voice coil that produces waves in the air that the ear detects as sound.

Crossover- An electrical circuit (passive or active) consisting of a combination of high-pass, low-pass and band pass filters used to divide the audio frequency spectrum (20 Hz - 20 kHz). The divided audio spectrum is then sent to individual drivers that specialize in limited bandwidths. Without a crossover each driver would be receiving the entire frequency range.

Crossover Frequency- Frequency at which a loudspeaker's crossover network divides an audio signal and sends it to different drivers.

Crossover Slope- The rate at which a driver attenuates as it starts to see unwanted frequencies. Specified as dB/oct.The higher the number, the steeper the slope, which results in a narrower zone where the sound transitions from one driver to another.

Crosstalk- Distortion caused by one channel introducing an unwanted signal into another.

CRT – (Cathode Ray Tube)- The type of TV monitor that most people are familiar with that makes an image by magnetically deflecting an electron beam aimed at the screen. CRTs are not “flat panel” TVs.

DAC- A Digital to Audio Converter. Converts a digital bitstream to an analog signal.

Damping- The attenuation of a resonant frequency over time.

Damping Material- Any material added to increase dampening . Acoustic fiberglass, polyester batting, or Polyfill inside the speaker enclosure can be used to dampen the woofer cone’s resonant frequency.

D'Appolito- Joe D'Appolito is credited with popularizing the MTM (Midrange-Tweeter-Midrange) type of speaker.

dB- (decibel) Also see: Decibel

Decibel- The measure of sound loudness.. One dB is considered to be the smallest change in sound loudness that is perceptible to the human ear.

dB/octave- See Crossover Slope

DBS- Direct Broadcast Satellite. See also: DSS.

Diaphragm- In a speaker, the part driven by the voice coil that moves, producing air waves that we perceive as sound. It usually has the shape of a cone or dome.

DiAural- A patented crossover geometry that which allows for proper communication and interaction between transducers (woofer, mids and tweeters). This new and innovative process results in fewer parts, less distortion, lower production costs, and renders the high frequency and mid range transducers virtually burn-out proof.

Diffraction- The bending of waves around small obstacles and the spreading out of waves beyond small openings (where small is defined as smaller than the wavelength).

Diffuse- Scattered; not concentrated.

Digital Audio-The representation of a waveform with bits of information that are discreet (non-continuous) in both time and amplitude. See PCM and Analog.

Dipolar, Dipole (Speaker)- For speakers, when opposing sets of drivers are wired out of phase with each other and fired in two different directions. This results in a cancellation of sound on axis so that the listener hears only sound that is reflected off of room boundaries Wall mounted “surround” speakers often employ this strategy. Also see: Bipolar.

Direct View TV- A television with a picture tube.

Discrete- In audio, refers to distinct, separate channels.

Dispersion- The spreading of sound waves as they leave a speaker.

Distortion- Audio distortion: The name given to anything that alters an original input signal other than changing its amplitude ( loudness.)

DIY- Acronym for do-it-yourself, usually referring to various hobbies, especially audio-related.

Dolby AC-3- Surround sound standard from Dolby Laboratories which incorporates six discrete (one of which is the .1 LFE) channels of information for the playback of video soundtracks.

Dolby Digital- A five-channel system consisting of discrete left, center, right and left rear, right rear channels. The AC3 standard also has a separate subwoofer channel for the lowest frequencies.

Dolby Digital EX- Also referred to as Dolby Digital 6.1, adds a rear, center channel to the existing left, center, right and rear speakers. This format requires a 6.1 processor or receiver and DVDs that are 6.1 encoded.

Dolby Pro Logic- Rather than producing surround sound from 5+ discreet channels, as later surround sound formats like Dolby Digital do, the surround information is synthesized from a 2-channel source. Since it is often used as a default format (when a 2-channel source is sensed as the input) newer, improved versions are still being developed.

Dolby Surround- Older than Pro Logic, Dolby Surround has been superceded by later, better formats.

Dome (tweeter)- A high frequency driver with a dome-shaped diaphragm.

Driver- A name for the parts of the loudspeaker which actually make sound. e.g. midrange driver, bass driver (woofer), treble driver ( tweeter). The term “driver” is used so that the term “speaker” can be reserved for the driver+crossover+enclosure system.

DSP- Digital Signal Processing. Used to alter a digital input signal. Some common examples include: time delay for the rear speakers, equalization for a subwoofer, filtering low frequencies out of satellite speakers and adding “effects” (like “concert hall”.)

DSS- Direct Satellite System.

DTS- Digital Theater Systems. A surround sound format that competes with Dolby Digital. Many listeners feel that it can sound better than Dolby Digital but there is a very limited DVD selection. More...

DTS-ES- The DTS-ES discrete 6.1 format that adds a dedicated rear channel for use with , 6.1- encoded DVDs and CDs.

DTV- Digital TV. A new system of digital television broadcasts.

DVD- Originally coined as Digital Video Disc or then changed to Digital Versatile Disc, upon adoption by the computer industry. DVD has the same physical dimensions of a CD, however it can hold much more information.

DVD-Audio- (music-only) An upgrade to CD audio. The extra memory space of a DVD is used to enhance sound by employing higher sampling and bit rates, up to 24-bits, 192 kHz sampling for two (stereo) channels at 74 minutes.

Dynamic Loudspeaker- Loudspeaker which uses conventional cone and dome drive elements exclusively.

Efficiency- Tells you what percentage of the power arriving at a speaker gets turned into sound (as opposed to heat). Often expressed as decibels/watt@ 1 meter (dB/w/m.)

Electrostatic Loudspeaker- These are usually very large flat panel loudspeakers. They must contain an on-board power supply to provide a high static voltage to the grid, which may be on one or both sides of the panel. The audio signal is applied to metal traces that cover the panel. The resulting interaction of the panel with the strong electrostatic field causes the panel to move thus creating sound.

EQ (Equalizer)- Electronic device that acts as active filters used to boost or attenuate certain frequencies.

Euphonic- Pleasing. As a descriptive audio term, usually refers to a coloration or inaccuracy that none-the-less may be sonically pleasing.

Fb or Fsb- A driver’s resonance frequency in free air or in a sealed box, respectively.

Fc- or Fcb- The system resonance frequency of a driver in a sealed box.

Ferrofluid- A Magnetic oil, usually applied around the voice coil of a tweeter. Its advantages are that it increases short-term power handling by conducting heat from the voice coil to the magnet structure and it damps the tweeter’s Fs, allowing it to work better with the crossover.

Filter- Any electrical circuit or mechanical device that removes or attenuates energy at certain frequencies while allowing other frequencies to pass. See Crossover Network, Crossover.

Flanging- Another term for phasing.

Flat- Term used to describe the most accurate tonal balance, indicating that there isn’t too much or too little of any frequency range (bass or treble for example). The term comes from the “frequency response” graph that shows this.

Frequency Response- The range and balance of sound across the audio spectrum Good sound reproduction requires that all audible frequencies (approx. 20 - 20,000 Hz) are reproduced at roughly the same volume, although the highest and lowest octaves are less important.

Front Speakers- These are the two speakers (right and left) placed in the front of the listening position.

Full Screen/Wide Screen- This legend appears on most 2-sided DVDs. Full Screen means the image will fill an entire 4:3 (standard) TV monitor, cutting off the sides of the film in order to do so. Widescreen shows the complete picture. But if you have a standard 4:3 TV, you will see black bands at the top and bottom. If you find these bands to be objectionable, a 16:9 or widescreen television is recommended.

Gain- The function of a volume control.

Gauge- Gauge is a unit used to measure wire thickness. The smaller the number, the thicker the wire. (i.e. 10-gauge wire is much thicker than 16-gauge wire). A change of 3 in the gauge # tells you that the wire thickness has doubled or halved. Also see: AWG.

Grain- A listening term. A sonic analog of the grain seen in photos. A sort of "grittiness" added to the sound.

H Haas Effect- The psychoacoustic effect that allows us to perceive direction. If a sound reaches both ears simultaneously and at the same loudness, the sound appears to be coming from directly in front of or behind the listener. Also see: Stereo.

Harmonic Distortion- Harmonic sound energy unintentionally added by an electrical circuit or speaker. It is expressed as a percentage of the original signal. See THD.

Harmonics- Also called overtones, these are frequencies that are multiples of the original or “fundamental” frequency. Harmonics extend in frequency beyond the audible range.

HDCD- high definition compatible digital. Pacific Microsonics' (now owned by Microsoft) trademark for their encode/decode scheme that allows up to 24 bit, 176.4 kHz digital audio mastering process, yet is compatible with normal 16 bit, 44.1 kHz CD and DAT formats. Sounds best on an HDCD compatible player, but will still sound better than a CD on a standard CD player without HDCD compatibility.

HDTV- The highest rung in the ladder of various DTV formats. HDTV requires three things: 1080 active scan lines, 16:9 widescreen ratio, and Dolby Digital sound.

Headroom- The ability of an amp to deliver more than its rated power for short durations. This capability allows an amp to reproduce musical peaks as though it were a higher power amp

Hertz- Denotes frequency in Cycles Per Second, (CPS): 20 Hz = 20 CPS. The “kilo” in kilohertz means “X 1000.”

High Pass Filter- A filter designed to pass high frequencies while attenuating low frequencies.

Home Theater- An audio and video system designed to reproduce the theater sound experience at home. Usually consisting of a 5.1 multi-channel surround sound receiver, DVD player, left, right front speakers, a center channel speaker, and two rear surround speakers. Six and Seven channel-discrete formats (DTS ES and THX EX, etc) have been recently introduced.

Home Theater In A Box (HTiB)- Any of several kinds of packaged audio-for-video systems designed to create an "instant" home theater; usually inexpensive and compact. Typically includes a multi-speaker complement plus a receiver or multichannel amplifier to drive the speakers. May function as a stand-alone 5.1-channel system or may be designed to add channels to an existing stereo or other audio system.

Imaging- The speakers’ ability to create the illusion of the original sound sources, like musical instruments, as being localized in space. Also See: Soundstage.

Impedance- The total opposition (resistance, capacitance and inductance) offered to the flow of an alternating current. You can think of impedance as resistance (Ohms) that can vary at different frequencies.

Integrated Amplifier- Single unit containing both a preamplifier and a power amplifier.

Interconnects- Cables that are used to connect components at a low signal level. Some examples include CD player to receiver, DVD player to receiver, receiver to powered sub, etc. Most interconnects use a shielded construction to prevent interference and use “RCA” type connections.

Interlace- Part of many broadcast TV systems. Here in the USA, refers to the NTSC standard where 1/2 frames are broadcast every 1/60th of a second. A complete frame takes two of these ? frames displayed taking up an actual 1/30th of a second. There are 400+ horizontal lines in each full NTSC frame... 200 per each 1/2 frame. One 1/2 frame is made up of the odd numbered scan lines, the other 1/2 frame contains the even numbered scan lines. The full frame is visible when the two 1/2 frames are merged (interlaced) to form a single image. Interlaced images contain motion artifacts due to the interlacing. Also see progressive-scan.

In-Wall Speakers- Speakers designed to mount flush with the wall and use the wall’s interior air space as its enclosure.

Letterbox- Term used to describe viewing a widescreen image on a NON-widescreen TV monitor. The result is a full width imagewith black bars at the top and bottom of the TV monitor screen. Similar to "Widescreen." Also see: FullScreen/Widescreen.

LFE- Low Frequency Effects. A home theater audio term that refers to low frequency sound effects in a multi-channel surround format, such as Dolby Digital or DTS. The .1 actually denotes the very low effects extracted from any of the surround channels (front left, front right, center, rear left, rear right, etc). If a subwoofer is present in the home theater sytem, all of the extracted audio information is routed to the subwoofer.

Line Doubler- Specially designed device to double the number of Scan Lines in an (usually) NTSC monitor or projector. Enhances picture quality by reducing jitter and video artifacts.

Line Level- Also know as “low-level”, an audio term referring to the signal before power amplification. In a system with separate pre- amp and power-amp the pre-amp output is line level CD players, VCRs, DVD players, Laserdisc Players etc., are connected in a system at line level, usually with shielded RCA type interconnects. (For techies, it's a signal level between -10dBu and +30dBu.)

Lines of Horizontal Resolution- Lines of horizontal resolution refers to visually resolvable vertical lines per picture height. It is measured by counting the number of vertical black and white lines that can be distinguished an area that is as wide as the picture is high. DVD has 720 horizontal pixels ( on both NTSC and PAL discs), the horizontal resolution can be calculated by dividing 720 by 1.33 (for a 4:3 aspect ratio) to get 540 lines. VHS has about 230 lines, broadcast TV has about 330, and laserdisc has about 425).

Loudness Control- On a preamp or receiver, a function that boosts lower and, to a lesser degree, higher frequencies of the audio spectrum to compensate for the way your ear works at low volumes.

Low Pass Filter- A filter designed to pass low frequencies while attenuating high frequencies.

Luminance- Abbreviated Y. That part of the video signal that carries the information on how bright the TV signal is to be; The black and white signal.

Magnetically Shielded- This means that a loudspeaker has its magnetic field contained so that it can’t discolor or damage a CRT type TV monitor.

Matrix- A technique of storing more than one audio channel on a single channel. Dolby Surround is an example, where the center and surround channels are electronically extrapolated from the left and right channels of a stereo signal. This contrasts with today's discrete digital channels.

Maximum Power Rating- The maximum wattage that an audio component can deliver/handle as a brief burst. Most reputable manufacturers will provide both an RMS (continuous) and Max power rating. Typically, the given value for the maximum power rating is twice to three times that of RMS.

Midbass- Mid frequency bass, usually frequencies just above the sub-bass range, from around 100 - 200 Hz or so.

Midrange- The mid band of an audible signal, typically anywhere between 200 Hz and 2 kHz. Also refers to the drivers that specialize in these frequencies.

Mini-plug- Eighth-inch connector (jack and plug) used primarily for headphone or speaker connections in personal electronics.

Noise- An undesirable signal that is unintentionally added to a picture or sound signal.

Nominal- In home audio there are two main uses of this term: 1. nominal power rating- minimum amount of power recommended for a speaker. 2. nominal impedance- theoretically the minimum impedance a speaker will present to the amplifier.

Nonresonant- Materials that don't vibrate much or absorb vibrations, which can affect sound reproduction; materials often included in the construction of a loudspeaker.

NTSC- National Television System Committee. The NTSC standard has a fixed vertical resolution of 525 horizontal lines. There are 60 fields displayed per second. A field is a set of even lines, or odd lines. The odd and even fields are displayed sequentially, thus interlacing the full frame. One full frame, therefore, is made of two interlaced fields, and is displayed about every 1/30 of a second. See also: Interlaced.

Octave- An octave is a doubling or halving of frequency. 20Hz-40Hz is often considered the bottom octave, 40Hz to 80Hz is the bass octave. 80Hz to 160Hz is the upper bass octave, etc.

Ohm- The unit used to measure electrical resistance. (The word Ohm comes from German physicist Georg Simon Ohm, 1787-1854) An 8-ohm loudspeaker presents a good level of resistance and will be compatible with most modern amplifiers.

Output- The sound level produced by a loudspeaker.

Overload- A condition in which a system is given too high of an input level. A common cause of distortion or product failure.

Oversampling- A digital technique of representing a waveform with more bits of information than would theoretically be needed. Oversampling is used to reduce the amount of noise (unintended information) in a signal.

Passive- Device neither having nor requiring power.

Passive Radiator- A diaphragm (either a drone cone that looks similar to a woofer or a flat plate) that reinforces the woofer’s bass output; acoustically similar to a port. Also see: Bass Reflex.)

PCM- Pulse Code Modulation. PCM is a digital scheme for transmitting analog data. The signals in PCM are binary; that is, there are only two possible states, represented by 1's 0's. This is true no matter how complex the analog waveform happens to be. Using PCM, it is possible to digitize all forms of analog data, including full-motion video, voices, music, etc.

Peak Power- the recommended highest power capacity of an amplifier or speaker.

Phase- In audio, phase refers to the timing relationship of two or more waves. It's especially important to be sure that your speakers are wired "in phase." This means that the drivers of your speakers are moving in and out at the same time. If your speakers are "out of phase" there will be significantly less bass, and a loss of stereo imaging.

Phono Plug- Same as an RCA-type plug.

Pink Noise- Noise that has equal energy in each octave.

Ported Enclosure- A type of speaker enclosure that uses a duct or port to increase low bass output.

Preamplifier (or pre amp)- A preamp is the control center of an audio/video system. Source component switching is done here, as well as volume and balance control. This component generally has some degree of signal amplification associated with it. AV receivers contain both a preamp and amplifier.

Progressive Scan- A display which scans consecutive lines of a screen at a rate of 60 times a second. This offers a smoother image than interlaced which scans every other line of a screen at 30 times per second. Also see: Interlaced

RCA Connector- Standard pin plug or jack used to connect audio and video components, developed by RCA Laboratories. Also known as a phono plug or jack, even when applied to non-phono equipment.

Rear Channel Speaker- A Loudspeaker that is located beside or behind the listener in a surround sound system.

Rear Projection Television- A video monitor/television where the image comes from behind the screen- sometimes directly projected or sometimes bounced off of 2 or more mirrors to appear on the back of a screen.

Receiver- An audio (and/or video) component that combines a pre-amplifier, amplifier(s) and tuner in one chassis. A home theater receiver will also contain multi-channel surround decoders, such as Dolby Digital and DTS.

RMS- Acronym for root mean square. A power measurement (measured in watts) used in audio to help rate the continuous power output of an amplifier or input capability of speakers.

S/N- Signal to Noise Ratio. An audio measurement of the residual noise of a unit, stated as the ratio of signal level (or power) to noise level (or power), normally expressed in decibels.

SACD- Super Audio CD. A joint trademark of Sony and Philips for their proposal for the next generation CD-standard comprised of a 1-bit, 64-times oversampled direct-stream digital SACD format.

Satellite Speaker- A small loudspeaker designed to fit more easily into the interior decor of a home. Typically they need to be used with a subwoofer.

Scan lines- Scan lines are the horizontal lines that make up the video image on a television or video monitor.

Sealed Enclosure- A loudspeaker cabinet without any vent or portholes. For a given sized enclosure, they are either not as efficient or don’t go a low in the bass as ported enclosures.

Sensitivity- The loudness of a speaker at a given voltage. Usually measured at 2.83 volts, at 1 meter straight in front of the speaker and excluding reflected energy.

Signal To Noise Ratio (S/N)- How much relevant content (signal) something has compared to non-relevant content (noise); expressed in decibels.

Sine Wave- A pure, single frequency wave. Audio signals are sine waves or combinations of sine waves.

Slew Rate- This is a term used to describe how quickly the output of an amplifier can follow its input. Slew Rate is usually measured in V / msec. The higher the value, the better the amp is at reproducing the subtle nuances and dynamics associated with sound reproduction.

Soft Dome Tweeter- A tweeter with a dome-shaped diaphragm. made of soft material such as silk, or woven/processed synthetic material.

Sound Pressure Level (Spl)- Measured in decibels (dB); is an expression of loudness or volume. A 10db increase in SPL requires 10 times the power but sounds only twice as loud . Live orchestral music reaches brief peaks in the 105db range and live rock easily goes over 120db.

Soundstage- Listening term. Perceived width and depth of music (or sound) especially for stereo reproduction. A set of speakers with good soundstaging means you can localize a separate position for each instrument and voice, emulating a live performance.

Spade Lug- Type of speaker wire connector shaped like the letter "U" and designed to fit around a speaker binding post.

Speaker-Level- A signal that has already been amplified.

Spider- The flexible material that suspends the inside portion of the cone from the speaker frame.

SPL- See sound pressure level.

SPL Meter- Device used to measure sound loudness; often used to measure and balance the loudness of each speaker in a home theater system to "tune" a room.

Standing Wave- A sound wave that “hangs around” because its length fits between two parallel walls so that its reflection reinforces the itself. This results in muddy, booming bass; problem is variable depending on shape and size of room and sometimes can be minimized by placing speakers farther out from the wall.

Stereo- Derived from the Greek word meaning solid. A two channel audio format designed to provide the illusion of a three- dimensional, holographic image between the speakers.

Subwoofer- A speaker designed to specialize in low-frequency reproduction. A true subwoofer should be able to at least reach into the bottom octave (20-40Hz). Although any location will result in bass that appears to come from the satellite speakers, they usually sound best when placed near the front speakers.

Subwoofer Output- Line-level (or low level) output on an A/V receiver or preamp that transmits only low bass signals to the subwoofer where it is amplified.

Surround- The outer suspension of a speaker cone usually made of foam or rubber.

Surround Sound- An attempt to recreate the acoustical and ambient information of a particular environment, such as a church, a stadium, a movie theatre, etc using more than a stereo pair of loudspeakers.

S-VHS- Super VHS - A recording and playback format requiring an SVHS VCR. As the name implies, it's better than standard VHS, producing about 480 lines of resolution. (Standard VHS displays about 240 lines.)

S-Video- A video transmission method that is better than composite video, not as good as component video. S-video separates luminance (black and white information) and chrominance (color information) signals. The S-video interconnect cable somewhat resembles a computer PS-2 cable.

Sweet Spot- A listening position that yields the best results, usually equidistant from the front (two or three) loudspeakers.

THD- Acronym for Total Harmonic Distortion.

THX- An acronym for Tomlinson Holman Experiment, THX is a set of technical standards and performance criteria developed by Lucasfilm to ensure that moviegoers see and hear a film at optimum performance levels, "as the director intended". This comprehensive set of standards includes rigorous specifications designed to optimize equipment, room acoustics, background noise levels, and projection and viewing angles.

THX Select- THX certification designed for optimal performance in smaller listening environments and at lower volume levels; conceived for rooms of less than 2000 cubic feet. (See THX)

THX Surround EX- a home theatre surround format engaging an additional rear surround speaker, allowing for dramatic 360 degree surround sound. This technology made it's theatrical debut with the opening of Star Wars: Episode I The Phantom Menace.

THX Ultra- THX certification designated for ultra high-end A/V gear, as opposed to THX Select, which is aimed at more moderately priced equipment; conceived for rooms of more than 2000 cubic feet. Also see: THX

Timbre- Tone color. It's the quality of sound that makes one instrument or voice sound different from another. For example, a flute has a different timbre than a clarinet.

Tonearm- On a phonograph (record player), the arm that acts as the support mechanism for a phono cartridge.

TOSLINK (Toshiba link)- In home audio, it refers to another term for "optical audio cable. Originally implemented and developed by Toshiba.

Total Harmonic Distortion (THD)- The percentage of the total sound that is unintentionally created harmonics from the original signal. . When comparing audio components, the lower the number, the better.

Transducer- A Device that converts one type of energy-electrical, acoustical, magnetic or mechanical-into another. Examples include a phono cartridge, magnetic record or playback head, speaker, microphone or cathode ray tube (CRT).

Transient Response- The ability of a speaker to respond to any sudden change in the signal without smearing or blurring the sound. A speaker that can react quickly to rapid changes in sound has "good transient response".

Treble (highs)- High audio frequencies, the upper end of the audio spectrum, usually reproduced by tweeters, – about 2 kHz and up.

Tri-wiring- The use of three pairs of separate speaker wire from the same amplifier to separate bass, midrange and treble inputs on the speakers.

Tweeter- Transducer responsible for reproducing the higher frequencies of an audible signal, typically active above 3 or 4 kHz.

Two-way- A type of loudspeaker that divides the audio spectrum into two parts , usually to be fed to a woofer and tweeter.

Vented Enclosure- See Bass Reflex.

Voice-matched- Speakers that are "voice-matched" have the same timbre or tonal quality. Voice-matched speakers in a home theater system will result in a convincingly seamless encompassing sound.

Warmth- Usually refers to a sound quality that results from not having more than the natural amount of treble. The opposite of “bright”.

Watt- A unit of electrical power. A watt of electrical power is the use of one joule of energy per second. Watts of electrical power equals volts times amperes.

White Noise- A full audio spectrum signal with the same energy level at all frequencies. White noise has much more treble energy than pink noise.

Widescreen- In home theater, a viewing aspect ratio wider than 4:3 (which is the typical television ratio). There are various widescreen formats, one of which is 16:9.

Woofer- A loudspeaker dedicated to producing low frequency sound.

Y-adapter- Any type of connection that splits a signal into two parts. An example would be a connector with one female RCA jack on one end, and two male RCA jacks on the other end.

YpbPr- another term for component video.