The Astin Trew Dictionary of Hi-Fi Terms 2008 We have compiled this A-Z of terms as a ‘quick guide’ for you. We've kept away from very detailed explanations, as there are many other places on the internet where it is possible to find more detailed and technical information on every topic and term covered below. As technologies advance and more audio (and visual) product goes digital, we hope this A-Z might be useful if you come across terms you are not familiar with.
3 way loudspeakers A loudspeaker which divides the incoming signal into three different frequency bands (normally through an electrical circuit crossover) for distribution to three drivers, normally, a bass, a mid range and high frequency tweeter. 4 way loudspeakers A loudspeaker which divides the incoming signal into four different frequency bands for distribution to drivers.
considerable economies for long distance power transmission. Virtually all the counties in the world use either a 50 or 60 hertz frequency for their power systems. Europe, Australia and India use 50 hertz. The Americas and Japan use 60 hertz. See also DC. AC-3 The encoding scheme used in Dolby Digital, the name by which it is now more commonly known. Acoustic suspension Also called infinite baffle. A design for the enclosure of a loudspeaker.
Amp Short for ampere, or for amplifier. In the former sense, the amp is a unit of electrical current. Amps equal volts divided by resistance (or impedance) in ohms. Amplifier A component or module of a component that increases the amplitude of an electrical signal. Voltage amplifiers and current amplifiers are optimised to provide amplification for specific purposes. See also power amplifiers and preamplifiers. Amplitude The level of an electrical signal, usually measured in volts.
A-weighted signal to noise ratio more accurately reflects how a system's noise performance will be perceived than an unweighted measure. B Baffle A solid surface surrounding a driver in a loudspeaker. The lower the frequency of the sound produced by the vibrating cone of a driver, the more apt it is to simply cause air to rush from one side of the cone to the other, rather than produce the compression waves that constitute sound.
allowing sub bass units to be placed away from the stereo speakers in 2.1of 5.1 set ups. Bass extension An imprecise term concerning how low in frequency a loudspeaker or subwoofer can still operate to produce usable output. A typical bookshelf-sized speaker may manage a bass extension of 80 hertz (say, at -10dB), a good floor standing speaker may manage 30 or 40 hertz, an inexpensive subwoofer 40 hertz, a middling one 25 to 30 hertz, an expensive one 16 hertz.
Bit The smallest unit of digital information. A single bit can carry just one of two values: 0 or 1. There are eight bits in a byte, 1,024 bytes in a kilobyte, 1,024 kilobytes in a megabyte, 1,024 megabytes in a gigabyte and 1,024 megabytes in a terrabyte. Sometimes, though, the traditional 1,000 is used rather than 1,024, leading to confusion. A bit should generally be abbreviated as lower-case 'b' (compared to 'B' for byte). Thus 128kb/s means 128 kilobits per second, whereas 128kB means 128 kilobytes.
Cantilever The thin rod within a turntable's cartridge that transmits the movement of the stylus in response to a record's groove to the interior components of the cartridge that generate the electrical signal. Carrier A sine wave which may be modulated by a signal to form an AM signal. The frequency of the carrier must be significantly higher than that of the modulating signal.
In practice, there is no such noise, so initially it can be hard to see the purpose of this. Then when you consider that for most music the amplitude of the signal reduces as the frequency increases at around 6dB per octave, you can see that the amplitude of the higher frequency components would be very low and, consequently, subject to increased quantization noise. Boosting the higher frequencies significantly reduces this noise accordingly.
incorporate class D designs. The jury is out on whether they ultimately offer the same fidelity as more conventional class A/B designs. Cliff effect Where the degradation of a signal's reception does not gradually increase with a reduction in signal quality or strength, but maintains full quality until some threshold, at which point the signal collapses into incoherence. Analogue transmissions tend to degrade gradually.
Codec Compression/Decompression. A system which compresses a signal in some way for storage or transportation and then decompresses it at the point of delivery. Examples are MPEG, Dolby Digital and DTS. These systems use a codec to reduce the amount of data in the signal. Other forms of codec, particularly in the days of analogue audio systems, compressed and then decompressed the dynamic range of the signal, not to reduce the size of the signal but to reduce noise levels.
picture to the TV is therefore via either component video connections (in which case, the TV reconstitutes the original RGB signal required for its CRT), or RGB (in this case, the DVD reconstitutes the RGB signal). Composite video This is the way that the three component video signals are wrapped together to form a single signal, suitable for TV broadcast or carrying on a single two-conductor cable.
Crossover distortion A small discontinuity (or, at least, nonlinearity) in a signal when a transistor-based amplifier circuit switches from positive to negative operation. This is addressed by Class A and Class A/B designs. Sometimes called 'zero cross distortion'. Crossover frequency The frequency at which a signal is handed from one component to another. This applies in loudspeaker crossover networks and base management systems.
into account the impedance of the wiring between amplifier and loudspeakers, nor the impedance of the speakers' own voice coils. Consequently there is only a modest performance gain between a damping factor of, say, 60 and one of 600. DAT Digital Audio Tape. A compact tape developed in the late 1980s by Sony which stores audio in PCM format. The tapes look very similar to the MiniDV tapes used in digital video cameras, but are somewhat larger, measuring 71mm wide by 53mm deep and 10mm thick.
Destructive interference Where two signals, added together, act in opposition to each other and reduce the signal level. For example, bass from a subwoofer may, at certain frequencies, bounce from a nearby wall and that reflected signal may, if arriving back out of phase, interfere with bass still coming directly from the subwoofer to effectively reduce the output at that frequency. But it is also likely, at other frequencies, to result in constructive interference. Digital As opposed to analogue.
Dispersion The degree to which loudspeakers spread their sound production in all directions, rather than directly to their front. All loudspeakers widely disperse their bass. But as the wavelength of a sound nears the size of a driver's cone diameter, the sound tends to become more directional. Distortion An inaccuracy in the reproduction of a signal. In the case of audio, it is normally regarded as being composed of harmonic distortion and intermodulation distortion.
it was developed by them, but the name above seems to have come into common currency. Dolby HX Dolby Headroom eXtensioin. Not to be confused with the various sorts of Dolby noise reduction, Dolby HX is a process that improves the high frequency, high level recording performance of magnetic tape, particularly compact cassettes. Dolby noise reduction It was the invention of an effective noise reduction circuit by Ray Dolby in the 1960s that got Dolby Laboratories onto the road to where it is today.
matrixed into two channels. The Dolby Surround decoder extracts the additional channel, known as the surround channel, and sends it to a pair of rear or surround speakers. This surround channel is limited in frequency range to 1007,000 hertz. Driver The moving part, or parts, of a loudspeaker. These are usually woofers (bass drivers), midrange drivers and tweeters (high frequencies). There are a number of different driver designs.
receivers incorporate DSP programs to generate ambient multichannel sound from stereo sources. DST Direct Stream Transfer. Lossless compressed DSD. DTS Digital Theatre System. A high quality digital surround sound compression format capable of carrying multiple channels of audio. While using perceptual encoding like many other systems, it uses much lower levels of compression. DTS claims that it first uses non-lossy compression techniques to reduce or eliminate the need for perceptual encoding.
through this layer to extract data from the bottom layer. Such a disc has, in single-sided format, a capacity of 8.5GB, rather then the 4.7GB of a single layer DVD. DVD Digital Versatile Disc or Digital Video Disc. In the former usage, it is the 12cm optical disc capable of holding masses of data for computer use, video, still pictures or audio. DVD Audio Digital Versatile Disc - Audio.
DVD+RW A rewritable (i.e. recorded material can be erased or over-written) recordable DVD. DVD Video Digital Versatile Disc - Video. This is the form of DVD which primarily holds DVD Video material, movies or music videos. All the DVD Video material resides in a folder on the disc called 'VIDEO_TS'. DVD-VR A recording mode offered for DVD-RW discs which differs from the standard DVD-Video mode.
excursion is necessary because output level is related to the area of the cone and the excursion. A smaller driver in a subwoofer can only provide equivalent output levels by allowing a greater excursion of the cone. Another example of excursion is the stylus of a cartridge. When playing a stereo LP it moves from side to side and up and down. Each of these is referred to as the excursion (horizontal and vertical) of the stylus.
EQ Equalization. An adjustment to the frequency response of some piece of equipment or process in order to achieve a desired outcome. It might be part of a standard process (eg.RIAA Equalization) designed to overcome physical limitations, or it might be used to correct unwanted frequency response inaccuracies imposed by a room. Excursion The degree of fore and aft movement of a mechanical component in an audio system. Loudspeakers, for example, produce sound by vibrating their drivers' cones or domes.
audio cassette undergoes this, it produces rapid variations in the playback frequency. At the slower end of the scale, it can sound like an unwanted tremolo or vibrato. At higher rates it can add an unpleasant harshness to the sound. Flutter is specified in per cent and specifications of more than around 0.1% are unacceptable. Digital sources such as CDs are immune to flutter because they lock their playback speed to a solid-state timing device. FM Frequency Modulation.
that the Middle C of a piano has a frequency of 261 hertz, we are actually talking about its fundamental frequency, not that of the harmonics without which a piano note would have no distinguishing character. G GB Gigabyte See gigabyte. Gigahertz A measure of frequency: 1,000,000,000 hertz. GHz Gigahertz See gigahertz. Gigabyte A measure of memory storage, a gigabyte equals (i.e. 1,024 x 1,024 x 1,024 or 230) bytes, 1,048,576 (i.e. 1,024 x 1,024 or 220) kilobytes or 1,024 megabytes.
Hass Effect Also known as the Precedence Effect. The human ears do not rely solely on different loudness’s to determine the direction from which a sound is coming; they also use timing. It is often the case that timing trumps loudness. If the same sound arrives from two different directions, the ear will tend to identify the direction of the source as that of the first sound to arrive, even if the other sound, arriving a few milliseconds later, is significantly louder.
1080i and 1080p. 720p has a resolution of 1280 lines by 720 vertical lines and 1090i and 1080p of 1920 by 1080. 720p displays each frame in full (progressively), while 1080i, displays each frame as one of two interlaced fields. Most High Definition screens will scale whatever source they are fed to fit the screen but will look their best when fed a source at their native resolution.
around nine decibels higher output than equivalent non-horn loaded loudspeakers, which means they can produce the same output from just one eighth of the power required for conventional speakers. This can, in turn, mean lower harmonic distortion because driver excursion is significantly reduced. Hybrid discs Optical discs which provide more than one format. Many SACDs are hybrid, consisting of two layers.
Impedance A measure of electrical resistance and reactance. These are the properties of a component that limit the amount of current that can flow through a circuit. Resistance affects the DC part of the electrical current, while reactance affects the AC part. Measured in ohms. Infinite baffle Another term for acoustic suspension.
Jack plug, jack or TRS connector. Familiar from the larger type of headphone jacks (or plugs), these are widely used in professional audio as well. There are three common sizes, 6.4mm, 3.5mm and 2.5mm. They come in both mono (two conductors) and stereo (three conductors) versions. The latter type at 6.4mm size are often wired for balanced mono operation in pro-audio applications where XLR plugs/sockets are not appropriate.
Line level An electrical signal at a voltage level suitable for transferring a signal between components of a home entertainment system (for example, CD player to amplifier, amplifier to VCR). Most modern equipment operates with a maximum of level of not much more than two volts RMS. Line level signals demand high impedance inputs. At least 10,000 ohms is suitable, although the de facto standard is 47,000 ohms.
MB Megabyte. A measure of memory storage, a megabyte equals 1,024 kilobytes or 1,048,576 bytes. However, if used as a measure of hard disk storage, the 'mega' prefix normally means a round million. Mb/s or Mbps -- Megabits per second. A measure of the data flow rate for digital video from a DVD. Stands for millions of bits per second. Generally, the higher the number the better the quality. MC cartridge Moving Coil cartridge. See Moving coil cartridge. Memory stick A small, removable flash memory (i.e.
space savings. It preserves the original signal perfectly, even through multiple encoding/decoding cycles. MMC Multimedia Card. A small, removable flash memory (i.e. non-volatile) cartridge. MM cartridge Moving Magnet cartridge. See Moving magnet cartridge. Mono or Monophonic. Where just a single channel carries all the sound. Even if played back on a system with two or more speakers, the sound remains mono because the left and right front speakers are delivering identical signals.
some DVDs. This permits up to 7.1 channels of audio to be encoded, although only 5.1 channels is ever seen in practice and 7.1 is now obsolete. MP3 is one particular form of MPEG stereo. Multichannel sound Often called surround sound. Any system designed to deliver more than two channels (stereo) of sound to the consumer. The most common forms these days deliver 5.1 channels of audio. Some systems can process two channels, or even one channel, of sound to produce the effect of multi-channel sound.
form. Rather than replacing the analogue soundtrack (which is left on for broad compatibility), the Dolby Digital data is optically recorded between the sprocket holes on the edge of the film. OSD On Screen Display. The menus and information screens shown by TVs, DVD players, VCRs and some home theatre receivers on the TV screen. These make setting up these devices somewhat easier than those devices that lack them. Overtone See harmonic.
out of phase. Causes of phase shift include filters (especially those in loudspeaker crossover networks) and the (lack of) time alignment of drivers in a loudspeaker. Phono From phonogram. An adjective relating to systems for playing vinyl recordings, such as LPs. Thus the phono input of an amplifier is the input into which a turntable is plugged. This is usually equipped with an RIAA equalization circuit. RCA plugs and sockets are sometimes called ‘phono’ plugs/sockets in the UK.
the Never Connected power supply is perhaps the best design available, offering a high degree of isolation from the ‘dirty’ mains. Switch mode power supplies are used in some audio applications but they tend to inject noise into the signal path and are not favoured by most audio product designers. PSP Pit Signal Processing - a digital watermark feature used on SA-CD.
Reactance The aspect of impedance which varies according to the frequency of the signal it is affecting. Measured in ohms. Receiver In the stereo world, an amplifier with a tuner built in. Often used as short hand for home theatre receiver. Region Code A system built into DVDs that is intended to prevent the playback of DVDs from one part of the world in DVD players sold in another part of the world. There are six region codes. The United States is Region 1. Europe and Japan are Region 2.
the phono preamplifier of the playback equipment reverses this EQ, boosting the bass back to its proper level and handily cutting the treble. This last has the welcome effect of substantially reducing the hiss produced by the scraping of the stylus within the groove. Note: old-style ceramic cartridges did not require this second step of reversing the EQ because their frequency response characteristics roughly approximated this anyway. RMS Root Mean Square. A measure of voltage or (incorrectly) power output.
SACD Super Audio CD. An audio format developed by Sony and Philips to take on DVD Audio. Both formats are being superceeded by 20 and 24 bit music downloads and bluray now. Sample One from a series of digital measurements taken of an analogue signal at regular intervals. The timing of the intervals is determined by the sampling frequency. The accuracy of the sample is determined by the sample's bit depth and the quality of the ADC.
that very modest figures like -20 or -30dB (typical of LP records) provide excellent stereo separation and imaging. More important is that the separation should not vary widely between different frequencies, since this could lead to a positioning mismatch between the fundamental and harmonic frequencies for particular instruments. Server (music) A computer device dedicated to the storage and analogue production of music from its library held in digital form on its hard disk.
S/PDIF Sony/Philips Digital Interface Format. A widely used digital audio protocol. It is used as the protocol for all consumer home entertainment equipment. It is distinguished from the professional AES/EBU protocol by incorporating the clock timing information in the main signal. Originally designed for 44.1 and 48 kHz and 16 bits, it now carries up to 96kHz and 24 bits, plus the bitstreams for the various compressed digital audio standards. The connections used are generally coaxial or optical.
usually applied to media / data that are distributed over the internet, where the delivery systems are either inherently streamed e.g. radio, music, television. The verb 'to stream' is also derived from this term, meaning to deliver media in this manner. Stylus A small diamond on the end of a cartridge's cantilever. This sits within the groove of an LP and picks up the vibrations recorded therein.
S-VHS tape recorders, and the TVs for them to plug into. Sometimes the term SVHS is incorrectly used instead of S-Video. Sweet spot The seating position or positions at which a stereo or surround sound system produces its best effect, particularly with regard to imaging.
the main speakers; so home theatre receivers incorporate a system to allow the sound to these speakers to be (adjustably) delayed by some milliseconds. Title The major divisions for content on a DVD Video disc. Typically the movie is in a single Title, while the trailer is in another Title and so forth. This is the equivalent of a Group on a DVD Audio. A Title is normally subdivided into Chapters.
Track The divisions within programme material on an LP, CD, SACD or audio DVD. Navigation is most easily achieved by using the forward and reverse 'skip' keys on the remote control. Transformer A device used to alter the voltage of AC electricity. This typically consists of an iron ring of some kind with two coils of wire wound around it. The input current is fed to one of the coils, which generates a magnetic field in the iron ring and which, in turn, generates a voltage in the other coil.
connected to the shaft. These appear in some very high quality turntables and offer particular advantages of high acceleration to speed, plus electronic speed control and stability. Tweak A subtle change to home audio or A/V intended to improve the sound. This could range from merely adjusting the system's controls, through replacing cables and experimenting with speaker positions, to all kinds of damping and isolating procedures.
higher horizontal resolution of around 300 lines, compared to VHS' 250 lines), which had beaten it to market. Eventually VHS prevailed through having longer record-playback times. There was also an electrically similar, but physically smaller, compact version of VHS called VHS-C for use in digital video cameras. Superseded by DVD-R. Voice coil The coil of wire that is attached to the back of the cone or dome of a loudspeaker driver.
unacceptable. Digital sources such as CDs are immune to wow because they lock their playback speed to a solid-state timing device. XLR A professional audio connection standard in which the signal pins are not connected to the shielding earth. This allows them to carry balanced audio signals. Most commonly seen in three pin versions (for mono) although there are also five pin (stereo) versions. Zero cross distortion See cross-over distortion.
