Welcome to the AVR Glossary. Here you'll find our definitions of the mostly frequently queried hi-fi and AV terms. We'll be adding to the glossary regularly, and you can too. Send your suggestions to editor@avreview.co.uk
5.1-CHANNEL Six discrete channels, usually front left and right, centre, surround left and right, and a subwoofer. 6.1 and 7.1 are also available.
AAC Advanced Audio Coding. A successor to MP3, which allows lower bit rates whilst maintaining higher quality. Used by Apple for its popular iTunes music player.
AAD Seen on commercial music sleeves, AAD means the music has been recorded and mastered in analogue but is stored digitally on the disc.
ADD Seen on commercial music sleeves, ADD means the music has been recoded using analogue technology, but was mastered (or often remastered) and stored digitally.
AMPLIFIER An amplifier can either come in two parts (a pre-amp and power amp) or integrated as one unit. It is used to boost signals so as to power speakers.
ANALOGUE Legacy technologies such as tape and vinyl store music as a direct representation of the sound wave. This is described as 'analogue recording'.
ANAMORPHIC Anamorphic DVDs include picture optimised for widescreen (16:9) TV sets. This eliminates the letterbox effect.
BALANCE Most speakers have a characteristic frequency balance resulting from emphasising or de-emphasising particular parts of the audio range.
BALANCED CABLES In cables which are said to be 'balanced', two cores carry the signal, plus and minus, while the screen simply carries out the job of screening.
BASS The lowest three octaves of the audio band. Low bass is the bottom octave (20-40Hz); mid-bass is the middle octave (40-80Hz); and upper bass is the 80-160Hz octave.
BASS REFLEXA speaker design whereby a port in the cabinet helps to deliver better bass reproduction
BINDING POST A speaker terminal designed for the connection of bare wires (and sometimes banana plugs).
BIT The smallest piece of digital data, either a '1' or a '0'.
BITSTREAM A fast method of converting digital data (from CD, DVD or MD) into analogue signals.
BI-AMP (sometimes tri-amp) Some speakers have separate access terminals to each drive unit allowing individual drive units to be driven by separate (matching) power amplifiers.
BI-WIRE (sometimes tri-wire) Loudspeakers with separate access terminals to each driver can be driven by separate cable runs between the amp and each driver.
BRIDGING Increasing output power by connecting two 'bridgeable' stereo amplifiers together, each working on a single channel.
CARTRIDGE Converts the impressions left in the surface of a vinyl record into an electrical signal by passing through the grooves left in the disc's surface.
CD-R Recordable CD that cannot be erased or written on to after it has been 'finalised'.
CD-RW Re-writable or re-recordable CD. Often early CD players are unable to playback CD-Rs.
CLASS A Amplifier in which positive and negative are amplified together, offering superior quality, but generates considerable heat.
CLASS B In this amplifying process, positive and negative are dealt with separately, with the output alternating between the two. Class A generally offers lower distortion, Class B tends to generate less heat.
CLASS AB Most amps operate in Class A for the first fraction of a watt and Class B thereafter.
CLIPPING This form of distortion occurs when an amplifier's output waveform is advanced too far and no more 'volts' are available to sustain increasing power levels.
CLOCK Any electronic oscillator used to generate a timing reference signal. Its purpose is to synchronise the data being taken from a disc by a CD or DVD player.
(DIS)COLOURATION A move away, usually owing to unwanted interference or poor quality components, from the 'true' sound of a recording.
COMPRESSION 1. Describes a method used by radio stations to minimise the audible difference between soft and loud parts of a track. 2. Refers to a digital treatment of music to allow greater amounts to be stored or broadcast within restricted space or bandwidth, usually by the removal of certain frequencies that are deemed to be inaudible.
CROSSOVER A simple electrical network which divides the full bandwidth signal received from an amplifier, sending different parts of the audio spectrum to the various drive units in a speaker ie bass, mid and treble. Various speakers have their crossover points set at different frequencies.
CRT Cathode Ray Tube, the conventional technology behind television sets and some high end projectors. Three different coloured tubes (red, green and blue) work together to create a colour image on the screen.
DAB Digital Audio Broadcasting. Digital radio uses frequencies in the band 217.5-230MHz in the UK. Broadcasters use varying degrees of compression which can cause the audio quality to vary greatly. Many national stations are only available on DAB.
DAC Digital-to-Analogue Converter. The stage in a digital component where incoming digital data is used to reconstruct an analogue (music) waveform.
DATA COMPRESSION See compression.
DDD Seen on commercial music sleeves. DDD means the disc has been reordered, mastered and stored digitally.
DECIBEL (db) Measures strength of sound waves. A change of 1db marks an audible increase, where an increase of 10db effectively doubles the volume.
DIGITAL OUTPUT Allows an external DAC, in a mixer or recorder for example, to process or record the digital sound.
D-ILA Direct-Drive Image Light Amplification - a projector technology developed by JVC
DIPOLE SPEAKERS Two speakers within a single cabinet which fire in different directions, out of phase with one another. By providing a less focused sound source, the dipole aims to replicate the ambient wash of sound in a large auditorium such as a cinema. This is deemed to more closely represent the cinema experience.
DISTORTION Changes or additions to the sound signal that are undesired.
DLP Digital Light Processing. A projector screen technology developed by Texas Instruments that uses individually controlled micro mirrors on a Digital Micromirror Device (DMD) to produce an image.
DOLBY B, C and S Noise reduction systems used on the recording and playback of audiotapes.
DOLBY DIGITAL A popular compressed digital audio format which usually contains five or more discrete channels, e.g. 5.1 which includes side and rear channels, a centre speaker and a sub-woofer.
DOLBY DIGITAL SURROUND EX A development to Dolby Digital whereby the rear channel is matrixed, to offer a more enclosing surround sound experience.
DOLBY HX PRO A means of ensuring that high frequency recorded sounds are delivered to the tweeters, while lower ones remain with the woofer.
DOLBY PRO-LOGIC DPL is a forerunner to Dolby Digital that 'steers' sound from a stereo source to the front, centre and mono surround channels via an analogue matrix.
DRIVER/ DRIVE UNIT The business part of any loudspeaker is a transducer which converts electrical energy into acoustic energy, e.g. bass driver, tweeter.
DSD Direct Stream Digital is the coding format used for SACD and offers a frequency response of over 100kHz with a dynamic range over 120dB. It has over four times the data capacity of CD.
DSP Digital Signal Processor. An integrated circuit that decodes the digital audio streams. In 5.1 processors it separates the left from right and front from rear as well as managing the various bass options.
DTS Digital Theatre Sound. Competitor to Dolby Digital with a reduced compression ratio that can, in theory, produce higher quality audio.
DTS EX MATRIX The DTS equivalent to Dolby Digital EX.
DUAL DISC Technology which allows a DVD disc to have an additional CD layer, allowing DVD-Audio discs to be played in standard CD players.
DVD-AUDIO High-resolution DVD variant which offers up to 192kHz bandwidth and 24-bit dynamic range. DVD-A discs play in all standard DVD players.
DVD VIDEO Video recorded on a disc physically similar to a CD. Large capacity allows for high picture quality, as well as additional features, such as surround-sound audio for example.
DVD-R/-RW A recordable/rewriteable DVD format developed by Pioneer.
DVD+R/+RW An alternative DVD format developed by Phillips.
DVD-RAM The DVD format developed by Panasonic. The method of recording allows the user to watch the beginning of a program whilst the remainder is still being recorded.
DVI-D A digital connection allowing for the transmission of video and audio without the need to convert it to analogue.
DVR Digital Video Recorder. Another term for Personal Video Recorder.
DYNAMIC RANGE The range between the smallest and largest audio signals in Hi-Fi sound.
ELECTRICAL DIGITAL Any digital connection that uses an electrical cable rather than the optical variety. This includes the balanced ('AES/EBU') interface.
ELECTROSTATIC A type of speaker that uses a pair of thin panels, rather than a conventional drive unit. Positive and negative electric charges are passed over the panels, one stationary and one moveable, to generate sound - two positive or two negative charges repel each other while a positive and negative attract each other, which leads to movement and so sound production. Characteristically, they tend to offer enhanced stereo imaging (largely due to the lack of room resonances generated by the design) but can require careful placement due to producing a tightly focused soundstage.
FILTERS Inherent to digital sounds reproduction, filters affect the way a sound feels to the user.
FREQUENCY High pitched are said to be high frequency. The inverse is true of low sounds.
FREQUENCY RESPONSE The range of frequencies which a loudspeaker will reproduce.
HDCD High Definition Compatible Digital. A higher quality codec used in some CD players.
HDMI High-Definition Multimedia Interface. A digital connection for linking DVD sources to displays. Similar, yet slightly superior to DVI-D.
HDMI 1.3 The next generation of HDMI. It promises an increase in bandwidth from 165MHz to 340MHz which offers potential for greatly improved picture and sound.
HDTV High-definition TV. A set of digital television standards that offer the highest resolution and sharpest picture.
HERZ (HZ) Measures frequency in cycles per second.
HORN LOADING Improves efficiency of drive units using a construction that's shaped like a horn.
IMPEDANCE The resistance to the flow of an electric current in a circuit. This is effectively the electrical load that a loudspeaker presents to the amplifier which is driving it and is measured in ohms.
JITTER An insidious form of distortion that can occur with digital audio and which is caused by inaccuracies in the clock which is used to regulate the conversion of data into analogue audio.
KBPS Kilobits per second. A digital data rate measurement system which is often used with highly compressed formats such as AAC, DAB, MP3 etc. The higher the amount, the better the quality generally is.
LCD Liquid Crystal Display. A type of display that requires very little depth and thus can be found in compact projectors and flat-panel displays.
LCOS Liquid Crystal on Silicon - a projector technology. Pioneered by Canon in the UK.
LFE Low Frequency Effects. The sounds which pass through a subwoofer.
LINE LEVEL Almost every source component (except phono cartridges) gives an output in the region of 1-2 volts - this is 'line level'. Amplifier inputs labelled 'CD', 'tuner', 'aux' or 'tape' are all designed for this input level, while record players may need a separate 'phono stage'.
LOSSLESS COMPRESSION A system for reducing the number of data bits (density) in a musical signal without corrupting the original.
LOSSY COMPRESSION Reduction in data bits using a system that predicts what should be, and what shouldn't be, 'audible' in a musical signal.
LUMEN A unit of measurement (of luminous flux) that refers to the amount of brightness given off by a light source. Lumen ratings of projectors are taken as an average of photometer readings at several points on a screen.
To compare, a wax candle gives off around 13 lumens, a 100 watt bulb around 1,200. The amount of lumens necessary in a projector can vary according to needs. In a darkened room, 500 lumens may be enough, but in a conference room with normal lighting or daylight, 1,000 or even 2,000 lumens would be better.
MIDRANGE The middle three octaves (more or less) of the audio band, where the ear is most sensitive, usually between 160Hz-3kHz.
MINIDISC 64mm optical disc format developed by Sony. New Hi-MD technology has seen disc capacity jump to 1gb.
MONOBLOC A mono power amplifier. Two monoblocs are required if a stereo output is required.
MOVING COIL A type of turntable cartridge. Transfers the physical movement of the stylus into electrical energy via coils that move.
MOVING MAGNET A type of turntable cartridge. Transfers the physical movement of the stylus into electrical energy via a magnet that moves in relation to a fixed coil.
MP3 MPEG layer 3 Lossy compression format for digital audio that reduces data content to allow music to be transferred via the internet or allow hundreds of CDs to be stored on a computer or hard disc device.
NICAM CD quality stereo sound broadcast alongside analogue TV broadcasts.
OEM Original equipment manufacturer.
OHM Measure of resistance to current (impedance). The lower the impedance of a speaker, the harder it is to drive.
OUTPUT IMPEDANCE A measure of resistance to alternating current. Sound sources with low output impedance (ie below 100 ohms) can help to ensure that they will be compatible with most amplifiers, even with long interconnect cables.
PCM Pulse Code Modulation) The digital coding system for analogue waveforms used for CD and DVD. Quality is limited by the oversample and bit rates used - CD is 44.1kHz/16-bit while DVD-A is capable of 192kHz/24-bit. SACD's DSD technology offers a bit rate of 2.8224 Mb/s, which is 64 times CD's sampling rate.
PHONO STAGE Turntables output sound at lower levels than other devices, such as CD players. Thus, to ensure they are suitably audible, it is necessary to connect them to a 'phono stage input', or use a 'phono pre-amp'.
PLASMA Currently the leading technology behind large flat-screen televisions. Here, an electrical current is passed through neon/xenon gas, causing it to react, creating the desired 'pixel'.
PMPO A measure of power often used to describe 'ghetto blasters' or mini systems. As it is the peaks of the wave that are measured it makes the system look more powerful than it really is when compared to RMS power.
POWER AMPLIFIER Prepares audio signals sent from s source for output to loudspeakers.
POWER HANDLING The highest safe power for speakers.
PREAMPLIFIER The section of an amplifier used to control the sound, can be integrated with a combined amplifier, used alone with active speakers, or connected to a separate power amp.
PRESENCE BAND The critical section of the audio spectrum where midrange and treble meet.
PRO LOGIC See Dolby Pro Logic
PROGRESSIVE SCAN Realises DVD image frames in their entirety, allowing for flicker-free clearer images. Traditionally, a system of interlacing was used, where rapidly refreshed horizontal lines were interchanged to recreate the overall image.
PVR Personal Video Recorder. A hard-drive-based device used for recording TV programmes.
QUANTISATION NOISE A form of distortion (noise) caused by errors in the description of the musical signal by the digital code.
RDS Radio Data System. RDS sends extra data along with a conventional FM radio signal allowing RDS receivers to display station names etc.
SACD Super Audio CD. A Sony/Philips format launched in 1999. Based on DSD coding, it offers high-resolution stereo and/or multi-channel sound. Modern SACDs often have an additional CD layer which also allows them to be played in normal CD players, but without the advantage of SACD sound.
SAMPLE RATE The number of samples taken of a particular signal in a given amount of time (usually one second). For CD this is 44.1kHz or once every 0.023msec. DVD supports both 48kHz and 96kHz.
SIGNAL TO NOISE RATIO Represents the difference between the level of the audio signal, and any interference. The larger the figure, the purer the sound.
SATELLITES The side and rear speakers in a surround system.
SENSITIVITY The volume that a speaker will offer for a specific voltage input, expressed in decibels per watt (dB/W).
SIX CHANNEL OUTPUT DVD players are available with built in decoders, so that they can be connected to several power-amps, or a single amplifier, with a six channel input.
S/PDIF (Also SPDIF) Sony/Philips Digital Interface, a standard audio file transfer format. Developed jointly by Sony and Philips, S/PDIF allows the transfer of digital audio signals from one device to another without having to be converted first to an analogue. This prevents the quality of the digital signal degrading during transfer to analogue.
SUBWOOFER Extra low frequencies driver which can be used to augment both stereo and surround systems. Also known as either 'sub' or 'woofer'.
SUPER-TWEETER Ultra high frequency driver which extends the frequency range upward, beyond the range of human hearing i.e. above 20kHz. In theory, they can offer more space to the sound, even though its upper frequencies, extending to 50kHz and beyond, are not technically audible.
SXRD Silicon X-Tal Reflective Display - a projector technology developed by Sony.
TAPE LOOP Sends signals out of an amplifier to a tape recorder, a separate input is provided so that the recorder can send the signal back to the amp for monitoring.
THX Specification set originally designed by Lucasfilm to ensure optimum reproduction of film sound and video in cinemas and which includes amplifier power and speaker dispersion characteristics. In home cinema set-ups THX Ultra is more stringent than THX Select.
THROW RATIO Throw ratio describes the relationship between the distance of the projector from the screen and the size image produced. You would use this to ascertain what size screen is suitable for any given room.
TONEARM A metal shaft attached at one end to a turntable which holds the cartridge used to play a vinyl record.
TOSLINK Toshiba's proprietary optical fibre signal transmission system.
TRANSISTOR/MOSFET The two most common varieties of power semiconductor used in solid state amplifier output stages.
TRANSMISSION LINE A type of speaker enclosure in which the back-force of a bass driver is routed through an internal channel before being ported to the outside of the cabinet. This technique allows relatively small speakers to produce deeper bass.
TRANSPORT Part of an audio or audio/video playback system which reads the data from a CD, DVD or SACD but does not decode that data from its digital form into an analogue form suitable for audio or video reproduction.
TRANSIENTS Sudden, short, sharp events in a musical track, such as a finger click or a cymbal smash. These sounds are difficult to reproduce
TREBLE High frequencies at the top end of the audio band i.e. above 3kHz.
TWEETER Treble driver.
TWO/THREE-WAY SPEAKERS Speaker crossovers generally split the signal into two or three frequency bands. A two-way speaker doesn't necessarily have two drive units, as additional units can double up. Floor-standing speakers are more likely to be three-way designs.
VALVE A legacy amplification device still popular with many owing to it's warm sound. Consists of electrodes in a glass vacuum.
WATT Unit of electrical power. The 'watts per channel' (WPC) rating is the maximum average undistorted power that an amp can deliver to a typical speaker.
WIDESCREEN Aspect ratio used in the vast majority of contemporary TV programming and film making. So as to avoid the image being clipped, or appearing in a 'letterbox', a widescreen TV set is required.
WOOFER The drive unit that produces the bass frequencies.
AGGRESSIVE Bright up-front sonic character.
AMBIENCE The relaying of the sonic character of an acoustic space, such as a concert hall in which a recording was made.
ANALYTICAL Of high detail.
ARTICULATE Clarity of individual voices or instruments within a recording.
ATTACK The initial burst of a sound.
BALANCE The relationship between the left and right channel in Stereo sound.
BODY A full sound with a complete bass.
BOXY Sound polluted by cabinet resonance.
BRIGHT Tonal emphasis on the upper midrange. Opposite of 'dark'.
DARK Tonal emphasis on the lower frequencies. Opposite of 'bright'.
DECAY The fadeout of a sound following its initial attack.
DEFINITION The ability of a component to realise the minute details in sound essential to High Fidelity.
DEPTH Perception of a recording encompassing the space of the original performance.
DETAIL The delicate elements of sound that are lost when using inferior equipment.
DRY A sound devoid of reverberation owing to atmospherics of a room.
DYNAMIC The presence of a wide sonic range.
EUPHONIC A form of distortion that enhances sonic interpretation, and is often associated with valve amps.
FAST An effective reproduction of transients.
FORWARD A sense of music being forced upon the listener.
GRAINY A sound lacking in finesse.
GRIP A sound solidly rooted to the bass.
GRUNT Synonymous for grip.
HARD Aggressively metallic sound quality.
HARSH Grating listening experience.
IMAGING Offers the sense of an instrument's location within a room.
JUICY A pleasing sound, with life and vitality.
LOW LEVEL DETAIL The very quietest sonic events in a recording.
MUSICAL A sense of overall completion and stability in a sound.
NATURAL A perceived link to realism through a recording.
OPAQUE Clouded, lacking in clarity.
OPEN A clean upper midrange and treble.
PACE A strong delivery of beat and musical timing.
PRESENCE Offers the sense of an instrument's location within a room.
PRESENCE RANGE Upper midrange.
SEISMIC Bass you feel rather than hear.
SIBILANCE Clarity of the 'S' sound, often most noticeable on radio broadcasts.
SNAP A combination of good pace and speed gives a good representation of live performances.
SPEED Fast, pacey systems offering accurate timing.
STURDY Robust sound.
THICK Lacking in low frequency articulation.
THIN A light bass provision.
TIMBRE The tonal character or an instrument or voice.
TIMING A combination of precision in tempo, speed and pace.
TRANSIENT Effective transient response allows for greater clarity and detail.
TRANSPARENCY An ability to hear through the track to reveal all elements of the recording.
TWEAK To tune a system or component in an attempt to gain optimum performance.
TWEAKER A person who enjoys the above.
VEILED Lack of detail owing to poor transparency.
WARM A fullness in the low midrange.
WHDI Wireless High Definition Interface. A proprietary technology for wireless transfer of high deinition video, developed by AMIMON.