Hifi & Audio jargon explained

During the course of this site you will have noticed that there is a great deal of jargon contained within the numerous pages on offer.  

Although I have tried to keep the jargon down to a minimum there is still some areas that may need explaining or expanding on for those readers that particularly au fait with all the terms.   

With that in mind I will try to offer my best explanations and descriptions of the various terms.  If there is anything missing or wrong, please don't hesitate to contact me and I'll sort it out best I can.

 

Shortcuts to headings.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

 

A

A  Abbreviation for Ampere (see also Ampere).

 

AAD  Seen on CD cases.  Meaning music was recorded in analogue (A) and mastered in analogue form (A) - the first two A's - but stored digitally on the CD.

 

ABSOLUTE PHASE

In the recording and reproduction chain, there are many opportunities to reverse polarity, especially when hooking up speaker wire between the amplifier and the speaker. For most people there is no difference in the sound when the polarity is reversed. However, some audiophiles argue that there would be a difference in the sound if the polarity were to be changed for something like an explosion and if the reproduction could reproduce all the low frequencies in the sound. The sound of an explosion would have positive polarity, you see.

 

AC  Abbreviation for Alternating Current.

 

AC-3  See Dolby Digital.

 

ACOUSTIC FEEDBACK

If a portion of the sound output from loudspeakers can somehow excite the turntable or stylus of the system, a new, unwanted signal is created, which is in turn amplified by the electronics and reproduced by the speakers. If this signal is in phase with the original signal at a particular frequency (usually bass) a tremendous resonance (oscillation, a form of positive feedback) can occur in the room. Even small amounts of acoustic feedback can cause a considerable amount of distortion.

The careful positioning of speakers and turntable is the usual remedy to the problem. Placing the turntable anywhere near the speakers is usually a mistake.

An effect similar to acoustic feedback occurs when vibrations from walking in the room are transmitted up to the turntable from the floor. Generally if a turntable is positioned so that it is free from this kind of vibration, it will also be safe from acoustic feedback.

CD players and amplifiers are a lot less susceptible to acoustic feedback, but it does exist, and precautions sometimes help.

Another example of acoustic feedback (this time at high frequencies) is the squeal that occurs in microphone hookups where output from the speaker re-enters the system through the microphone.

No matter what the frequency, even if the gain of the amplifier is not high enough to cause oscillation, distortion in the form of a boost in response at certain frequencies will result from acoustic feedback. This can cause even the best speakers to sound "boomy". Ironically, the general recent improvement in low frequency response of quality systems has simply intensified the problem, so that acoustic feedback has become a major problem in quality sound installations.

 

 

ACOUSTIC SUSPENSION

Mounting a speaker in a hermetic or air-tight enclosure traps a fixed quantity of air behind it. The springiness of this air can effectively replace the suspension spring used in speakers to return the speaker cone to its "normal" position, hence the term "acoustic suspension" (either "air suspension" or "pneumatic suspension" would be more accurate). The ADVENT, the AR 3, and the EPI 100 are (old) examples of acoustic suspension speakers.

Acoustic suspension speakers are traditionally much less efficient than bass reflex speakers and therefore need more powerful amplifiers.

The major advantage of the design is simplicity and therefore simpler manufacturing and lower initial cost. However, any savings may be eaten up by the need for a more powerful amplifier. This is the hidden but unavoidable cost of inefficient speakers. 

 

ADD  Seen on CD cases.  Meaning music was recorded in the analogue form (A), mastered or remastered digitally (D), and stored digitally on the CD (D).

 

ALIGNMENT  Adjustment of a record-player cartridge relative to the groove on the disc.  Bad cartridge alignment causes distortion.  Tape heads also need aligned but unless you are an Electronic Service Engineer, it is best left to the experts.

 

ALTERNATING CURRENT  Electricity in the form of a sine wave (one with Positive and Negative halves forming a continuous waveform).  

 

AM  Abbreviation for Amplitude Modulation.   

 

AMPERE  Unit of current.

 

AMPLIFIER  Boosts signals from source equipment such as CD Players, Tuner, Cassette Deck to a level able to drive speakers.  Amplifiers are usually found in one box (Integrated) or can split into their individual components of Pre-Amplifier (handles witching and drive levels) and Power Amplifier (only contains electronics for powering speakers).

 

AMPLITUDE MODULATION   A type of Radio signal.  The carrier frequency varies in size (or amplitude) in sympathy with the modulating signal.  It is now commonplace to refer to the Long-Wave and Medium-Wave radio bands as AM, because all transmissions in them are made using Amplitude Modulation.

 

ANALOGUE  LP's, Cassette Tapes and Tuners reproduce signals that are non-digital but are directly relative to original signal.

 

ANTENNA  Used with Radio tuners for pickup of Radio Signal.  At Medium and Long-Wave frequencies is usually comprised of a long-wire or loop.   At VHF/UHF frequencies it is usually found in the form of a Directional-YAGI which has a single Driven Element (or Dipole) and sever Parasitic elements (or Directors) as well as having a Reflector element.   

 

ANTI-SKATING  Applied to tonearms on turntables to prevent them from swerving towards the centre.

 

ATRAC  A form of Data Compression.  Typically found in Sony Minidisc units.

 

AUDIO  Is the term that describes any sound between 20Hz and 20,000Hz (The recognized human hearing spectrum).  The term is also commonly used to describe any equipment used for sound reproduction.

 

AWG  American Wire Gauge.  Common method of measurement of wire diameters used in the US.  The higher the number the smaller the wire diameter will be.  In the UK this is normally expressed in mm (millimeters).

 

 

B

BACK EMF  The opposing electromotive force from loudspeaker units.

 

BAFFLE  

A baffle is a mounting for a speaker which assists sound radiation. A baffle is important because many sound wavelengths are longer than the speaker. The ideal baffle is flat and extends forever, creating a hemispherical sound wave.

The baffle is usually part of the cabinet. Sometimes special baffles are built for testing purposes.

When a small speaker is placed near the wall, the wall becomes part of its baffle.

The term infinite baffle is another way of describing the ideal baffle mentioned above. Actually, infinite baffle is often used to describe any situation where the back wave from the speaker is completely isolated from the front, as when a speaker is mounted in a hole in a wall.

 

BALANCED CONNECTIONS  A shielded signal cable usually found in Professional and High-End equipment.  Positive and Negative wires are shielded (for better interference rejection) in balanced connections.  Normal connections use the negative to shield the positive cable.  Balanced connections use a  three-pin XLR type plug.  These connections are also used in the AES/EBU digital format.

 

BAND-PASS

A variation of the bass reflex design. A speaker enclosure is divided into two chambers with the woofer mounted between them. One of the chambers is then vented with a tuned port. The tuned vent acts like a filter which limits the frequency response to a desired bandwidth, thus the term band-pass. This type of design is used primarily for sub-woofers and bass units of satellite systems.

 

BANDWIDTH  

The range of frequencies in which amplitude remains constant. Bandwidth is generally the subject of much controversy and confusion, since there is no standard method of measurement. Should speaker bandwidth be measured in a living room or in an anechoic chamber? How far should the microphone be from the speaker: Should the mike record reflected sound? Etc.

Bandwidth is another way of saying frequency response. 

 

BASS  This is the term usually given to Low frequencies, LF's are often tricky to reproduce in a lifelike manner.  When a review says that bass is slow it goes 'Whoompa-Whoompa' and can dominate the music.  In this case often referred to as being 'Overblown' or unrealistic.  The ideal is to achieve a good bass extension (i.e. low frequencies) allied to the speed (tempo) and rhythm of the music.

 

BASS REFLEX   

A speaker in an infinite baffle or a sealed enclosure uses only its front wave to produce sound. In a bass reflex or tuned port design, part of the back wave of the speaker is used to reinforce the front wave usually in the bass.

The back wave excites a resonant system which then radiates sound. This resonant system has two components: mass (actually air in this case), and the stiffness of the air suspension in the box.

The resonant system using the back wave is far more efficient than the primary system. Very little power excites great sound from bass reflex systems in the frequency range to which the port is tuned (generally below 100 Hz).

The increased output obtained in a bass reflex design can be used by the designer either to improve efficiency or to extend low frequency response.

An advantage of bass reflex design over acoustic suspension design is that the relatively higher efficiency of the former permits the same amount of bass to be produced with far less woofer travel or excursion. Since this generally increases linearity of the response, it produces less distortion, particularly in the low bass.

 

BELTDRIVE  Used to describe the method of driving the platter on a Turntable.  A belt the pulley an the motor on a Turntable helps to isolate the pickup from the motor and reduces motor noise.   Some high-end CD players are also fitted with belt drive.

 

BER  BitErrorRate.  The ratio of received bits that are in error, relative to a specific numbered referenced to a power of 10  i.e. 1:10

 

BIAMPING  Each drive unit of a speaker is driven by a separate amplifier.  A pair of  two-way speakers would need two mono amplifiers for each speaker.   Thus, four mono amplifier would be needed for this setup.   The main advantage of this setup is the increase in definition and imaging that comes from separating each amplifier channel from the other.  SEE ALSO BIWIRING and BRIDGED MONO.

 

BIAS  Usually refers to a High Frequency AC signal that is applied across the heads of a cassette deck when using Chrome or Metal Tape.  It is used to alter the frequency of the eddy currents on the head and thus keeps the record levels linear across the recording range.    BIAS also refers to the signal voltage needed to switch a transistor on.

 

BINDING POST  Speaker terminal with threaded collar for gripping bare wires and sometimes a socket for banana plugs, too.

 

BIT  A single piece of digital information, essentially an on/off signal.  Digital-to-Analogue converters turn strings of bits into audio signals.

 

BITSTREAM  One method of turning digital CD data in analogue signals.  Bitstream digital-to-analogue converters process single bits of information much faster than multibit DAC's, which work on chunks of digital data.

 

BIWIRING  Some of the benefits of Biamping can be had by biwiring but at a much reduced cost.  You need speakers that are suitable (one that has two sets of inputs and a split crossover) for this type of operation.  You send twin runs of speaker cable from the amplifier (again if suitable it should have two sets of outputs or speakers A/B) to each speaker.

 

BRIDGED MONO  This is a special mode that some stereo amplifiers can be switched into (the ROTEL RB970's for example).  What happens when you switch a stereo amplifier into Bridged-Mono mode it combines both the channels to produce just the one (mono) signal.  The output typically increases by 2/3rds and a 60Watt amplifier will increase its output to become an 180W one.

 

 

C

C  The symbol for Capacitance.

 

CABLES  Copper conductors are commonly used within Hifi cables.  The purity of the copper contained within the cables is usually expressed as a number of 'nines'.  Thus a cable claiming 'six-nines' or 6N would nominally be 99.9999% pure copper.  Cables can have many strands (multistrand) or one or more thick wires (solid core).  One area of confusion is with directional cables which have arrows marked on them, directional cables are usually setup so that the signal travels down the cable following the arrows.

I am skeptical about the directional properties of cables.  Manufacturers claim that the cable has fractionally less resistance in one direction due to the lay of the copper molecules presumably down to the direction the cable was drawn when manufactured.  With interconnect cables, although reportedly directional, the setup is slightly different this time.  The shield (not to be confused with the earth or 0v line) is usually only connected at one of the cable, this being the source end.

 

CAPACITANCE  A measurement of the charge capacity (or potential) on Capacitors (Electrolytic, Air spaced etc.)   Expressed in Farads, pF (Picofarads), uF (Microfarads), nF (Nanofarads) etc.

 

CAPACITOR  

An electronic element in which two metallic plates are close to each other but not in contact, with voltage on one plate affecting the voltage on the other. A capacitor will not conduct a direct current, but will allow alternating current to pass.

Capacitors have an impedance with respect to frequency which declines at a regular rate of 6 dB per octave. At low frequencies a capacitor therefore has high L, making it an excellent filter for keeping low frequencies away from a tweeter. Therefore, capacitors are common elements in crossovers.

 

CARTRIDGE  The device which actually plays the vinyl record.  It converts the wobbles in the record's groove into electrical signals for your amplifier.  SEE ALSO MOVING MAGNET and MOVING COIL.

 

CD  See Compact Disc

 

CD-i  Compact Disc Interactive.  A now defunct home-entertainment system introduced by Philips in the early '90's.  

 

CD-R  CD-Recordable.  Uses a special blank disc for use in a CD Recording unit.  Once recorded on it can't be erased, but once 'Finalized' can played in CD players (occasionally referred to as a WORM or WriteOnceReadMany).  CD-R discs are different from normal CD's in that the data side has a Gold/Green or Blue tint.   There are two distinct types of CD-R, those being Professional (for use in computer CD-R machines) and Consumer ones (for use in Hifi recording units).

 

CD-ROM  Uses the CD format as a Read Only Memory for computers.  The CD-ROM has a capacity 650MB on the 74minute discs and 700MB on the 80 minute ones.

 

CD-TEXT  A new system that was originally promised with the inception of CD during the early 80's.  The system allows CD players to display textual information such as Title / Track Names and Lyrics.  Only players from Sony and Kenwood are currently supporting this system and there are few discs available with data on them (Titanic OST being one).

 

CLASS A  An amplifier in which both the positive and negative halves of the input signal are amplified by together..  As a consequence they usually run hot as the transistors/tubes in the power amp are running for 100% of the input cycle.  A class A amplifier has a high quality sound but are very inefficient in their power consumption.

 

CLASS B  An amplifier in which the Positive and Negative halves of the signal are dealt with by two separate amplifier stages (also called Push-Pull).  Each amplifier stage amplified either the top or the bottom half of the cycle and switch off for the rest.  Because of this a class B amplifier is much more efficient and cooler but will not sound as good because of crossover distortion etc.

 

CLASS AB  A class AB amplifier is essentially a B Push-Pull amplifier.  The difference lies in their operation designs with respect to the output transistors.   A normal silicon transistor will start to conduct with a base voltage of around 0.6 or 0.7volts.  A class A or a class B amplifier will usually have their transistor biasing levels set for around 1.0volts which would be well within a transistors output curve where no distortion would occur.  Now here lies the difference, a class AB amplifier has its biasing level set around 0.5volts, just above the point where the distortion ceases.  Now because of this the transistor can only amplify the top half of the signal, hence the reason for having two amplifier stages.

 

COAXIAL  The name given to a cable which has a centre conductor with an outer shield running around the outside.  The two conductors are separated with an air core or dielectric.  See also Dielectric

 

COLORATION  Coloration is the name given when sound reproduction does not follow that of the original sound/tone of the music.  Coloration is undesirable and is usually referred to when for example when Bass becomes 'Boomy' or the mid-range sounds 'Nasal' or if the Treble sounds 'Splashy'.   All colorations, will spoil your enjoyment of the music though careful selection and setup of your Hifi equipment should minimize this.

 

COMPACT DISC  A standard 12cm disc, which stores information digitally, which are read by a laser optical system.  Originally designed for Music storage the CD is now used for many applications which include CD-R, CD-ROM, DVD amongst others.

 

COMPLIANCE  A measure of the springiness in a component.  Usually refers to cantilever suspension on stereo cartridges.

 

COMPRESSION  This is a system used by Radio and TV stations to reduce level differences between loud and soft parts of music and speech.  The actual unit that the BBC use in their transmitters is called an 'Optimod compressor unit' and thus compression is often referred to as Optimod.  The reasons for the use of the Optimod are twofold, one is to help maximize the sound for in-car use but more importantly to ensure that the drive levels for the transmitters don't reach saturation and cause wideband interference in the radio spectrum.

 

CONDUCTION  The transmission of an electrical signal down a wire or a component. 

 

CROSSOVER  A circuit that is built inside speakers which by the use of High-pass and Low-pass filter splits the signal from the amplifier.  High frequencies are fed to the Tweeter and Low frequencies to the Woofer.

 

 

D

D/A  Digital to Analog

 

DAB  

Digital Audio Broadcasting is the new radio broadcasting system set to supercede the current AM / FM systems.  This is a digital system that broadcasts radio digitally in a Multiplex form - one Signal carrying a multitude of radio stations.  First transmissions were aired in 1995.  Units are available for in-car use but as yet Hifi units are still scarce, with sets only available from ARCAM and KENWOOD at the present time (Jan 2000).

 

DAC  Digital-To-Analogue Converter.  This is a piece of electronics that turn on/off pulses (see BITS) into analogue sound.   Most CD players have a DAC built into them.  Separate DAC's can upgrade a CD player or other digital player / recorder (DCC, DVD, Laserdisc or Minidisc), or can be used with a dedicated CD transport.

 

DAMPING

Any form of resistance or friction, electrical, mechanical, or acoustic.

Most of the damping of woofers is caused by the amplifier (electrical damping). Fiberglass in speaker enclosures is another form of damping (acoustical damping). In tweeters damping may be accomplished by means of a magnetic fluid bathing the voice coil.

In general, damping reduces the amplitude of resonance

The careful control of damping is important in speaker design because resistance or damping is a factor in the calculation of Q, which greatly modifies speaker response across a wide audible frequency range.

 

DAMPING FACTOR  The ratio of a speaker's impedance to the output impedance of the amplifier which drives it. Since speaker impedance is usually around 8 ohms, and amplifier output impedance is generally less than .1 ohms, damping factors may reach or surpass 100.

Most amplifiers have comparable damping factors. An amplifier can be designed to create more damping effect, but it is not certain that a higher damping factor is better. Amplifier damping is often related to negative feedback, which is not necessarily a good thing. 

 

DAMPING FLUID

Damping fluid is not necessarily ferrofluid, but ferrofluid is so useful and versatile that it has completely replaced other types in loudspeakers

 

DAT  Digital  Audio Tape. A digital recording system that is mostly used by Audio Professionals but also has dedicated following in the US.  DAT uses a revolving head similar to the type that is used in a VCR.  The sound is arguably better than that of CD due to its usage of a 48kHz sampling rate.  

 

DATA REDUCTION  A system that lowers the amount of data needed to store music.  There are quite few systems in everyday use.  Sony's Minidisc uses an in-house system called ATRAC (Adaptive Transform Acoustic Coding).  Philips have a system in their DCC machines called PASC (Precision Adaptive Sub-band Coding).  Other types are MPEG (Motion Picture Experts Group) which is used in DVD and Digital Satellite and MP3 (MPEG 1 Layer 3).   All these systems remove signals that the designers think you can't hear.  I have used Minidisc and find it 'acceptable' but have found that MP3 just massacres the music, just my personal opinion. 

 

DC  Abbreviation for Direct Current.

 

DCC  Digital Compact Cassette was a home digital tape system from Philips.  It was backwards compatible with the existing base of compact cassettes.  DCC cassettes worked on 16bit and 44.1kHz digital signals with data compression supplied by a Philips designed PASC unit similar to the ATRAC system. Due to the popularity of Minidisc it has fallen into disuse and is no longer manufactured.

 

DDD  Seen on CD cases.  Meaning music was recorded (D) / mastered (D) and stored (D) digitally on CD.

 

DECIBEL (dB)  A measurement for showing changes and gain in sound pressure.  A change of +1dB is just audible, while a change of +10dB would sound as if the output had been doubled.

            For working out dB gain use:  10 log  Voltage out divided by Voltage in.  The result will be the dB Gain level.

DIELECTRIC  The name given to the insulation space commonly found between conductors in a cable.  Varying the space between the conductors in a coaxial cable also varies the impedance Z.

 

DIGITAL  Method of storing data used by CD Players, DAT, DCC, Minidisc etc.  The analog sound is converted to a stream of 0's or 1's, effectively on/off signals.  Before digital information can be heard from a loudspeaker it has to be converted to analog in a D to A converter.

 

DIGITAL OUTPUT  Usually found on the rear panels of CD players, DAT and Minidisc.  This allows the digital signal to be recorded or processed by an off board DAC.  The two main types of Digital Output are Electrical (Coaxial) and Optical (also known as Tos-Link or Fibre Optic).

 

DIODE  Originally a valve/tube device.  In its modern semiconductor form it is a essentially a one-way component, it will only allow the flow of electrons in one direction and will only conduct when it reaches its switch on voltage.  These components are made from Germanium (switches on at .2 or .3volts) and more commonly, Silicon (switches on at .6 or .7volts).

DIRECTIONALITY

At its highest frequencies, a speaker directs almost all of its sound straight ahead . At low frequencies, sound radiates equally in all directions. The former effect, referred to as "beaming", can be a problem in speaker design.

Beamed sound has a psychological effect which can be pleasant: it causes voices to sound more "up front". It can also be unpleasant.

STEREO EFFECT is exaggerated with beamed sound. If you get good dispersion, there's a lot of sound arriving at your ear in complex patterns: the first reflection, the second, etc. making it confusing to judge when the sound actually happened. The phase information used by the mind to derive the stereo image is emphasized when beamed. This is one of the appeals of earphones, where virtually all sound is beamed with no dispersion.

Some designers choose to use drivers in their directional range (or beaming range) in order to obtain the desirable effects of beaming. If the designer is trying to achieve a more linear speaker (with respect to dispersion) he will wish to eliminate beaming. This can be done by crossover design, using crossovers to deprive drivers of frequencies where they beam, or through driver design, since drivers can be designed so that they don't produce any sound at frequencies where they would beam. 

Though directionality is generally thought of as a high frequency problem, it also occurs at the midrange frequencies at the "high-end" of the woofer.

 

 

DISTORTION  Any loss or addition to a signal is deemed to be distortion.  Typical types of distortion that can be measured within equipment are Intermodulation (IMD), Transient Intermodulation (TIMD), Harmonic Distortion (THD).

 

DOLBY LABS  A very well known American company who are famous for developing Noise Reduction and Home Theatre standards and systems.

 

DOLBY B, C + S  Noise reduction systems developed by Dolby Labs to boost quiet signals when recording and reduce them on playback, thus cutting tape hiss levels.  Dolby B and C are common with Dolby S being less common but usually found on better recording equipment.

 

DOLBY DIGITAL  Also known as AC3.  This is the latest in home cinema 'surround' sound systems from Dolby Labs.  It uses five discrete channels of digital sound plus a separate subwoofer channel for lower bass extension.  It differs from most surround systems in that it has separate stereo signals for the rear channels instead of the usual mono.

 

DOLBY HX PRO  Developed by Dolby Labs.  Not a noise a reduction system but a way of recording high frequency information without introducing distortion.

 

DOLBY SURROUND  Encodes sound for rear effects channels into the stereo.  Needs to be replayed through a decoder to produce surround.

 

DOLBY PRO-LOGIC  Uses an extra centre speaker at the front, which locks the dialogue to the screen.

 

DOME TWEETER

The original appeal of the domed tweeter is that it physically resembles the spherical waveform which an ideal loudspeaker should produce. Actually, the real advantage is that the dome shape gives the tweeter a very rigid structure so that it does not deform at high frequencies as much as a cone tweeter, e.g. the dome shape resists deformation and therefore has a more uniform response.

The conventional domed tweeter is convex, with a voice coil of the same diameter.

 

DOUBLING

A speaker generally has some low frequency at which there is a dramatic increase in distortion; reviewers generally refer to this phenomenon as "doubling." The origin of the term may be the fact that most speakers have a tendency to produce the harmonics of any tone they are required to reproduce, and one such harmonic is double the original frequency. Also the loudness seems to double. In reality, it is the third harmonic which sounds less pleasant than the second, so that what is labeled doubling may in effect be trebling.

Another type of distortion often called doubling occurs when a speaker causes a low-frequency vibration in the grill-cloth assembly. Another occurs when a speaker goes beyond its normal limits of travel and hits up against its suspension or frame (bottoms out).

 

DRIVE UNIT  The name given to an individual speaker contained within a speaker unit  i.e. Woofer or Tweeter.

 

DROP-OUT  Momentary loss signal during tape recording or playback from a defect in the magnetic coating or from the tape momentarily losing head contact.  Drop-outs can also occur on CDs but it takes fairly serious disc damage.

 

DTS  Discrete-channel home cinema digital sound system.  A rival system to Dolby digital.

 

DUAL MONO  Some amplifiers are designed to keep the left and right signals separate throughout the amp.  This helps to minimize interference (or Crosstalk) between the two channels.  These amplifiers are often designed symmetrical with mirror image throughout.

 

DVD  Digital Versatile Disc.  A new format on CD with a huge capacity that carries both Audio and Video signals.  Most players will play also play standard CD's.

 

DYNAMIC RANGE  Measured in decibels (dB).  This the range between the smallest and largest signals reproduced by the system.The dynamic range of human hearing is about 130 dB. The dynamic range of symphonic music is about 100 dB. For a typical CD it is about 80 dB; for a typical LP, about 40 dB. The lower limit of dynamic range is determined by background noise; the more noise, the less dynamic range. The upper limit of dynamic range is determined by physical restraint: amplifier power, for example; for human hearing it is physical pain; for absolute sound, it is the elastic limits of air.

 

DYNAMICS  The level of changes present in music.

 

E

EARTH  Also known as GROUND.  Earth is the Zero volt reference for all electronic/digital circuits.

EARTH LOOP  A source of Hum that is clearly audible through Loudspeakers.  Usually at the Mains frequency of 50/60Hz and is caused by having a difference of potential at the earth.   It is usually caused by incorrect earthing of tonearms and turntables.

 

EFFICIENCY  The measurement of the electrical energy fed to a loudspeaker that is actually turned into sound.   Most loudspeakers are terribly inefficient having a typical efficiency of only 5% and horn loudspeakers only managing 30%

 

ELECTROMAGNETIC INDUCTION  This refers to the process where an electrical current is generated by passing a magnet through a coil of wire or vice versa.  This is the principle used in Loudspeaker drive units, Moving Coil or Moving Magnet cartridges.

ELECTROSTATIC 

The simplest form of electrostatic radiator is a capacitor in which one of the plates is allowed to move, causing sound waves. The force is created by the alternating electric field which comes from the amplifier. Adding a polarizing voltage to one plate of the radiator will usually improve efficiency and lower distortion, so many electrostatic designs use power supplies of their own. Very often high voltages are involved (up to 3000 volts) because efficiency increases with voltage. This voltage can be obtained from house current, in which case the speaker will plug into the wall, or from the audio signal. This latter technique causes some leakage and loss of signal, leading to clipping and a bit of distortion.

The area of the plate reached by electric current gets smaller as frequency increases. (It is, after all, a capacitor.) Designers can control what part of the plate current goes to by use of electrodes in the plate, by use of multiple plates, and by controlling the conductivity of the material itself.

Polyvinylidene (of Saran-wrap fame is often used for plates because it has the right combination of conductivity and low weight. Mylar can also be used.

 

EMI  Electromagnetic Interference.  External signals that interfere with those being produced by an electronic component

 

EQUALIZATION

Years ago, recording studios used speakers which were chosen primarily for efficiency rather that bandwidth. People in recording studios had no idea what kind of high and low frequency response was going onto their records. The introduction of the equalizer allowed them to change the power to the speaker to make up for its deficiencies, and a lot of studios can now hear stuff they couldn't hear before. Therefore the quality of sound on records, particularly in the last five years, has improved a great deal. This has in turn caused speaker manufacturers to become more and more interested in the high and low frequency response of their products.

The improvement in records has also had beneficial effects on cartridge design. In turn, the improvement in cartridges allowed the recording industry to make yet another round of improvement through better hearing. This is, perhaps, the best example of symbiotic effect in audio. Also true, of course, with speakers and other components.

The introduction of CD's and digital technology has accelerated this process even more.

 

EQUALIZER

A component with lots of knobs, each one representing a certain bandwidth, or frequency division (an octave or fraction of an octave) which allows you to boost or decrease energy going to a speaker in that range. The result is that you can compensate for speaker limitations or acoustic distortion in the room itself. Now common in recording studios and becoming more common in living rooms.

 

F

FEEDBACK  Acoustic or structure-borne vibrations that interfere with the operation of audio equipment.   If a turntable is place too close to a loudspeaker the deep bass vibrations may be picked up by the stylus and amplified again and again causing extreme problems with the sound.  If a sound from a microphone is amplified through speakers and the microphone picks it up again, this is usually called HOWL-AROUND and is the reason why radio DJ's use headphones.

 

FERROFLUID

Ferrofluid is a trademark of Ferrofluidics, Inc. It is truly a space age material, a magnetic fluid, originally created for lubricating ball bearings in space. The liquid has tiny magnetic particles attached to the fluid base the way soap attaches particles of dirt. This fluid flows toward stronger magnetic fields.

In speakers, ferrofluid can be used in the gap of a tweeter magnet. Because of the fluid's magnetic properties, it is held in the gap and cannot run out. The presence of this fluid helps cool and therefore protect the tweeter by improving conductivity between the coil and the frame. ferrofluid also helps lower distortion because it prevents air movement in the gap. (This eliminates the possibility of spurious whine or whistle.)

Once sold at more than $100 an ounce, now a bit cheaper, this fluid is more in the class of optimization than luxury. The net result is that the loudspeaker can take greater power input and produce greater amounts of sound without burning out tweeters.

 

FIBRE OPTICS  Transmissions of signals by means of light fed down glass fibres.  These cables are commonly known as TOSLINK in the UK.

 

FILTER   Something which limits the bandwidth of transmission. A filter can be electrical, mechanical or acoustic. Typically, filters are hi-pass, low-pass or band-pass, referring of course to frequencies. For example, the suspension of an automobile is a low-pass filter, hopefully blocking all but the very slowest bumps from the tender sensibilities of the passengers.

 

FLUTTER  Rapid speed instability on tape or vinyl leading to fluctuations in pitch.  This is caused by transport problems.

 

FREQUENCY  Frequency was originally described as cycles per second, now simplified to Hz. (See HERTZ).  An example of frequency is a single musical note.  The frequency of a second hand on a clock is one cycle per minute 1/60 Hz.  A single frequency is a series of identical waves. The numerical value of the frequency is the number of complete waves that pass a single point in one second.  High-pitched sounds have a high frequency and low-pitched ones a low frequency.  The human ear can receive sounds ranging from around 16Hz or 20kHz.

 

FREQUENCY RESPONSE.   See also bandwidth

 

FRONT END  The signal source in a system, e.g. LP or CD.  Also the stage in a tuner which handles signals from the antenna.

 

FUSE  Protection device included in all system as a safety system.  Usually a thin piece of wire contained within a glass or ceramic casing.  The fuse wire will burn out under overload conditions.

 

G

GAIN  The measurement of the difference between the level of a signal input and the signal output.    Usually worked out by dividing the output by the input to give a ratio.

 

GHz Gigahertz.  1,000,000,000,000 Cycles per second.

 

GROUND LOOP  The generation of undesirable current flow within a ground conductor.

 

 

H

HARMONICS  Multiples of a fundamental sine wave. 

Frequencies which are multiples of a basic frequency. For example, a 110 Hz note will have harmonics of 220, 330, etc. (known as the second, third harmonics, etc.) also called overtones. An ideal transducer should reproduce only the signal it receives, without introducing any of its harmonics. In reality, any physical or electrical device inevitably introduces some harmonics of the tone it receives, and this is know as harmonic distortion.

Since harmonic distortion is particularly easy to measure, it often occurs in specifications of audio equipment.

Even-numbered harmonics are pleasant to the ear; odd-numbered HARMONICS, not so pleasant. A flute, for example, produces mainly even-numbered harmonics; a saxophone produces many odd-numbered harmonics.

 

HDCD  High Definition Compatible Digital.  A coding system from Pacific Microsonics for CD which aims to reproduce better sounds.  Needs a decoder and filters to be built into the CD player to hear full effects.

 

HERTZ (Hz)  Measurement of frequency in cycles per second.  One Hz means one cycle per second.  Named in honor of the scientist Heinrich Hertz who first discovered sound waves.

 

Hi-Fi  Abbreviation of High Fidelity.  Literally means Honesty or Truthfulness.  In audio terms it means an accuracy to the original recorded sound.

 

HOME THEATER

Systems for the reproduction of movies and other audio/visual productions include as a minimum a television set. The most common configuration nowadays also includes a Dolby Prologic receiver and four, five or six speakers, which include the conventional Left and Right stereo speakers as well as a center speaker , a pair of rear channel speakers and perhaps a sub-woofer. dolby has introduced a newer system called "Dolby Digital" or "AC-3", which includes an amplifier with five equal channels. These can provide greater flexibility and realism than the Dolby Prologic system. The most elaborate Home Theater systems include large screen TV monitors and digital sources, such as laser disks, digital tapes or digital broadcasts from satellites.

 

HORN LOADING  Improves a drive unit's efficiency and output using a structure within the speaker shaped like a horn.  Works in a similar fashion to a trumpet on an old-fashioned gramophone.

 

HUMAN HEARING

Research into human hearing has shown that stereo or spatial information is usually considered more important by listeners than wide-bandwidth response. Listeners will usually choose narrow-bandwidth stereo sound over wide-bandwidth mono. Audiophiles might prefer the latter, and some even prefer wide-bandwidth mono to wide-bandwidth stereo.

It has generally been considered that stereo information is derived principally from the difference in timing in the sounds emanating from two different speakers. However, intensity of sound also plays a role in imparting spatial information, particularly at lower frequencies, and beaming also has an effect. 

Biologically, sound is transmitted from the eardrum to bones to the cochlea (a snail-like organ.) Because of the way it's built, various frequencies go to various parts of the cochlea. There are lots of nerves throughout the organ: various frequencies excite various nerves. The timing of the sound is transmitted into digital pulses, and a part of the brain acts as a decoder to tell you what frequency came to which ear when. A survival tool, "Down that path you get stomped by a rhino," and therefore remarkably sensitive.

Human hearing is not only sensitive; it's also educable. Example, few people hear the 15,750 Hz sound of the flyback transformer on a TV before it's pointed out to them; most do, after it has been. This constant re-education of hearing and continual widening of perceptual abilities can be a problem for the audiophile whose hearing improves faster than he can afford better equipment, or who enjoys high fidelity less as it teaches him to hear better.

The importance of hearing is seldom fully appreciated. It is actually a more direct sensation of reality than seeing. To say "hearing s believing makes a lot more sense than "seeing is believing."

It is now beginning to be accepted that better hitters actually hear the ball better as well as seeing it better. It is certain that in most sports, good hearing may be as important as good vision.

When using firearms in sports, as in trapshooting, sound levels become destructive. Firing 25 rounds without earplugs can cost you a portion of your hearing ability for life, and no amount of money spent on audio equipment will do much good.

 

Hz  Abbreviation of HERTZ

 

I

IF  Intermediate Frequency.  A frequency in tuners used to mix frequencies together to get a lower one out.

 

IMPEDANCE (z)  Electrical property.   The ratio of voltage (or electrical pressure) to current (or electrical flow or quantity). Neatly expressed in OHM'S LAW.

In a speaker, impedance is affected by resonance and by crossover components, so it is not necessarily uniform as a function of frequency. (In fact, hardly ever.)

The lower a speaker's impedance, the more current will flow into it from the amplifier. Most speakers offer enough impedance to protect the amp, but hooking several speakers in parallel to the same output terminals can effectively simulate a short circuit and blow the amp or at least a fuse. On the other hand, connecting speakers in series increases impedance and hence reduces amplifier efficiency.

A low impedance (z) draws a high current flow from the source, while a high impedance (z) draws a little.  This means that speakers with a low impedance (lower than 6-8 Ohms) are more difficult for an amplifier to drive.

 

INDUCTANCE  The name given to the measurement of an Inductor.  A type of electrical behavior very similar to capacitance. Any inductor in an electrical circuit will increase its impedance to an alternating current as frequency rises. This is called inductance. Inductors are therefore low-pass filters and often used as elements of crossovers to prevent high frequencies from getting to a woofer.

The coil of the woofer itself has its own inductance and therefore to some degree acts as part of its own crossover.  Measured in Henrys.

 

INDUCTOR  A coil used in conjunction with capacitors in frequency conscious circuits such as Loudspeaker crossovers. Also called a choke or a coil, usually made by winding a number of turns of wire around a form, which sometimes encloses a magnetic core. An inductor acts as a low-pass filter.

 

INVERTED DOME TWEETER

An important variation of the domed tweeter, invented in 1968 by Winslow. Burhoe. Shares the advantages of the domed tweeter, plus others.

Essentially, the inverted dome results in even greater rigidity than the domed tweeter because the dome, once inverted, can be reinforced (by the voice coil) at its weakest point, half way between the perimeter and the center. Moreover, the inverted design allows the use of a smaller-diameter voice coiL. Since dispersion is related to the diameter of the radiating surface, and since at very high frequencies the diameter of a tweeter's radiating surface is equal to the diameter of the coil, the inverted dome tweeter also provides generally superior dispersion.

Using the same amount of wire in a smaller-diameter coil also results in a longer voice coil which stays in the gap of the magnet more effectively, creating a more linear response. (Again, less DISTORTION.)

 

ISOBARIC ENCLOSURE

The practice of putting one woofer in front of another connected by a sealed enclosure, so that only one is exposed to the outside air. This system has the effect of increasing moving mass, thereby providing greater bass extension at the cost of efficiency.

 

 

J 

JITTER   The name given to the time or phase shifting of digitals that can cause synchronization errors.

 

K 

K  Abbreviation for KILO.  The mathematical name given to values of a thousand

 

KHz  1000Hz or 1KHz.  Also 1000 cycles per second.

 

KLIPSCHORN

Book shelf speakers seldom have efficiency above one percent. For the Klipschorn (an invention of Paul Klipsch), it's something about 30%. The horn-loading makes it far more efficient, but the speakers really have to be big. The Klipschorn principle uses the walls of the room as effective extensions of the speaker itself. This effect applies only to sub-woofer frequencies. 

 

KWatt  1000W or KiloWatt

 

L

L  Symbol for Inductance.

LASERDISC  A hybrid of the CD system that includes both Audio and Video playback.  Laserdisc uses a 12" optical disc like an oversize CD.  Popular through the 80's and 90's, Laserdisc has now been largely replaced by DVD but still has quite a following.

 

LINE LEVEL  Describes inputs to amplifiers which don't need amplifying before the amp can use them.  This term is often used when an amplifier doesn't have a Phono (for turntables) input.

 

LINEARITY  A general term referring to the accuracy of response of an audio component in terms of a particular measured parameter, such as frequency response.  

As opposed to non-linear. When dealing with cause and effect, an effect is linear when it is exactly proportional to the input. When you pull on a spring with a specific force, twice the force should produce exactly twice the deflection. In a speaker, twice as much power from the amplifier should produce exactly twice as much sound.

All devices have some degree on non-linearity, hence distortion.

 

LOAD  Electrical resistance is often referred to as the load.

 

LOUDNESS

In audio, a term which usually refers to the principle (documented by Fletcher and Munson) that the response of the human ear to sound is not regular, but varies enormously with the intensity or loudness of the music.

At very low levels both bass and treble frequencies seem to decline more than the midrange frequencies. Many audio amplifiers therefore have some form of loudness control which causes the amplifier to boost certain frequencies at low-volume playback.

 

LOUDNESS CONTROL

Ideally a loudness control should affect both high and low frequencies. Actually, many so-called loudness controls affect only bass response, therefore doing only half the job. This is worth investigating when buying an amplifier.

Ideally, at concert-hall levels of sound, the frequency response of the amplifier should be flat whether the loudness control is engaged or not. Accurate compensation requires two controls, a gain control in addition to the loudness control. The gain control must be used to compensate for gain variations in all elements of the system (speaker efficiency, room acoustics, room size, source level, amplifier gain, etc.) to set the amp to the one gain setting at which loudness contour will provide a realistic balance.

Loudness systems which consist only of a button to convert the volume control into a loudness control and back again can't usually provide exact compensation. As a result, many audiophiles have never heard music with proper loudness compensation.

Understanding loudness compensation is important because properly used it can provide the same sonic balance from a system at low listening level as at full volume. Loudness controls, though, are generally misunderstood and often are used simply to increase bass response (sometimes because people feel nervous about any deviation from "flat" response and fell vaguely that the loudness button is "legal" while the bass control is not.)

 

 

LOUDSPEAKER  A device for converting electrical energy into acoustic energy.

 

LP  Long Playing Record.  Usually a 12" diameter vinyl disc.

 

LW  Long Wave Band.  The frequency band that lies between 522KHz and 1611KHz, broadcasts are in AM.

 

M

MAGNET

The source of the magnetic field which interacts with electrical current flowing through the voice coil wire to produce the force which moves the speaker cone.

Alnico, which used to be the material of choice, has been mostly replaced by ceramic ferrites. In cases where the magnet has to be very small or very strong, a neodymium alloy is now used.

 

MAGNETIC FLUX  The measurement of strength of a magnet.  Also known as GAUSS.

 

MHZ  Megahertz.  1,000,000Hz  (One Million Cycles per second)

 

MICROPHONY  Unwanted microphone like behaviour from components.  In effect sound causes these components to vibrate at their resonant frequency and the vibration modulates the signal waveform.

 

MIDBAND  Frequency range where most of the instruments and voices are heard.  Vital if singers, etc. are to sound natural

 

MINIDISC  Sony's 64mmdisc that can record upto 74 minutes of sound.  Looks like a miniature computer disc but works optically like a CD on pre-recorded discs, or magneto optically in the case of blank software.

 

MONITOR  A compact loudspeaker used to gauge the quality in a recording or broadcast studio.

 

MONO  Single channel record/playback system.  All commercial recordings were mono until the early fifties when stereo was introduced.

 

MONOBLOC  An independent mono power amplifier.  Two are required for a stereo system.  Advantage is lack of interaction between channels.

 

MOVING COIL  Cartridges with a stylus connected to coil which moves in relation to fixed magnet creating electrical signals.  MC cartridges have a lower output than MM ones but sound better.

MOVING MAGNET  Cartridges with a stylus connected to magnet which moves in relation to fixed coil creating electrical signals.  MM cartridges have a higher output than MC ones but don't sound as good.

 

MULTIBIT  A type of digital to analog conversion in which ladder resistor networks are used to read the 14,16,20 or 24-bit words of a digital bit stream.

 

MUSIC POWER  See PMPO

 

mV  Millivolt  (1000mV = 1 Volt); 1000uV = 1mV)

 

N

NEAR FIELD  The region within approximately two metres of the loudspeakers.  Listening tests conducted in the near field reveal different aspects of a loudspeakers performance compared with listening in the far field.

 

NEGATIVE FEEDBACK

In general, feedback is the application of a portion of the output signal to the input signal of any system which has gain. The most common usage of feedback is in audio amplifiers, since distortion in the output signal of an amplifier can generally be reduced by feeding a percentage of the output signal back into the input of the circuit with polarity reversed (hence the term "negative feedback").

In fact since all design is a matter of trade-offs, any decrease in distortion obtained by this technique must be paid for by a decrease in gain in the amplifier. Since negative feedback is essentially a corrective technique with an inevitable trade-off cost, a better solution is to create an amplifier with so little DISTORTION that negative feedback is not required to correct it.

Since negative feedback changes the damping factor of an amplifier (and therefore changes Q, therefore changing the frequency response of the speaker) some attention should be paid to this question when choosing an amplifier since speakers may sound quite different when driven by amplifiers with different amounts of negative feedback.

 

 

NICAM  CD quality digital stereo television sound that is transmitted along the picture on an Audio sub-carrier.   A system devised by the BBC in the UK.

 

NOISE  Any unwanted sound other than the signal. 

Random sound at all frequencies. Produced everywhere, even by the collision of molecules in the air around us. (This noise is just below the level of sound audible to humans, but exists nonetheless.) In audio, noise is also caused by the flow of electric current through transistors, vacuum tubes, and resistors.

Since there is always noise in the listening environment, sound-producing systems must be turned up loud enough to mask the noise. This fact may become a problem with components, like amps, which produce their own noise, since internally-generated noise may increase faster than the musical signal as volume is increased. Though modern high fidelity equipment usually generates so little noise that this not much of a problem, some internally-generated noise always shows up nevertheless in almost all component-generated sound. 

Systems which are to be used in a noisy environment should include relatively efficient loudspeakers. In such environments, low efficiency loudspeakers may require too much power in order to come up to levels which effectively mask ambient noise. 

Examples include Tape Hiss, electronic noise generated by amplifier circuits, earth loop induced hum, and random hums, hiss and spurious electronic clicks and pops.

 

NTSC  National Television Standards Committee.   The American TV standard.  In the UK it is often referred to as "Never The Same Colour" due to its unstable nature when it was first introduced to the world.

 

 

O

OCTAVE

A frequency term: doubling or halving a frequency. Called an octave because it is eight notes of a musical scale.

 

OHM  Unit of resistance to a current.  Impedance of a speaker is measured in Ohms - generally the lower the figure, the harder it is to drive.

 

OHMs LAW   A common law used for working out values in an electrical circuit.    V is Voltage, I is Current (Amperage) and R is Resistance.  V = I x R,  I = V / R and R = V / I

 

ONE BIT  See Bitstream

 

OUTPUT  The audio signal exciting a component

 

OVERSAMPLING  Used in DAC systems.  Increases signal frequency, making it easier for conversion circuitry and ancillary systems to filter out unwanted signals.

 

OVERTONES

Same as harmonics

 

 

P

PARALLEL / SERIES  All electrical components can be connected either in series or parallel.  Their effect on the circuit may change depending on the the type of connection;

An inductor connected in series with a woofer will provide a simple low pass filter.  

A capacitor connected in series with a tweeter will provide a simple high pass filter. 

 An inductor connected in parallel with as series capacitor will help create a 12db high pass filter for a tweeter.

A capacitor connected in parallel with series inductor will help create a 12db low pass filter for a woofer.

Band pass filters can be created by means of a series capacitor and series inductor, or by a mixture of series and parallel capacitors and inductors.

 

PASSIVE  A circuit or component which does not amplify the signal.  Introduces very little distortion.

 

PASSIVE RADIATOR

A loudspeaker component that looks like a woofer but isn't, for it has neither voice coil nor magnet. Like a tuned port, a passive radiator is part of a secondary sound producing system used either to improve efficiency or to widen bandwidth by utilizing the real woofer's back wave.

A passive radiator may be loaded with more mass than can be obtained in a tuned port of standard size, so it may be the solution in a particularly small cabinet. A sales advantage of the passive radiator is that it often makes the buyer think he is getting a large woofer when he isn't.

 

PCB  Printed Circuit Board

 

PCM  Pulse Code Modulation.  The type of signal used in CD replay.

 

PHASE  

Sometimes called polarity, when it refers to the plus/minus of interconnections. In a more general sense, it refers to the timing of a waveform. Particularly important in stereo. Two speakers connected to the amplifier out of phase so that one is pushing (waveform is increasing) while the other is pulling (waveform is decreasing) will usually sound flat. Mis-phasing can cancel out most of the bass, particularly if the speakers are close together. Speaker hook-up wire is generally color-coded or otherwise coded so that both speakers can be grounded to the negative output connection of the amp, putting them "in phase".

PHASE is also important in each individual speaker system. Suppose you have a woofer and tweeter producing the same sound simultaneously. The timing or phasing of the sounds will be influenced by cross-over design, mass, , impedance etc.

In the more general meaning of phase, one complete cycle of a sound wave can be considered to be 360 degrees of phase. 180 degrees is one half way through the sound cycle, etc. As frequency rises, inductance alone can cause phase shifts of as much as 90 degrees. At the cross-over point phase shifts as great as 120 degrees are not uncommon. For this reason, crossovers are sometimes wired 180 degrees out of phase (by reversing wires) for a net reduction in mis-phasing or mis-timing.

Another interesting area of phase change is around woofer resonance. Right at resonance there is generally minimum phase shift, but phase does shift dramatically just above and just below resonance.

In a speaker with high Q, phase shift around resonance will be greater. There is some dispute and discussion as to whether one can actually hear this phase shift. Since variations in frequency response are often associated with variations in phase response, it's difficult to know which one is being heard. It's generally accepted that drastic shifts in phase are audible as distortion. To put it differently, it's desirable to have a system in which phase shifts only gradually with change in frequency response

 

PHONO STAGE  Stereo cartridges output signals at much lower levels than CD Players.  Many amps have the extra amplification built in but increasing numbers of amplifiers don't and require an add-on phono amplifier.

 

PILOT TONE  The 38kHz carrier tone of an FM broadcast signal.  The harmonic at 19kHz is often found to be present in FM signals.  Some tuner will remove this.  The MPX filter on your cassette should always be used when recording from FM tuners.

 

PMPO   The term PMPO is actually a cheat.  It means peak music power output and it's the maximum of power that a speaker can handle. Actually, if you feed an 80W PMPO rated speaker with 80W of power it will blow in less than a second (computer speakers).   Power has to be specified in watts RMS (which is 0.707 of the true voltage).

Output power (W) is voltage (V) multiplied by current (I).  W=V*I Voltage and current are measured as RMS values. Than you can calculate
power.

A speaker rated 80W PMPO is nominally 4W RMS rated. When you divide the PMPO value with 20 you will get the REAL rated power.
For example, lets take an Aiwa stereo, there is a sticker at the front which screams 450Watts PMPO.  Well, when worked out it is actually 23Watts RMS, big difference.

PMPO is fake, it's cheating.  Never buy something which rates power in PMPO

 

POLARITY  A special case of phasing (either 0 or 180 degrees, plus or minus).If you touch a battery's terminals to those of a woofer, the woofer will move in one direction, either in or out. The convention is that if the woofer cone moves out, the positive terminal of the battery is touching the positive terminal of the woofer. In this case the polarity is positive. If the battery's terminals were reversed, the woofer cone would move in, representing negative polarity , or a reversal of polarity.

 

POTENTIOMETER  The device used to provide the volume level setting.  A Potentiometer is usually a variable resistor.  Often shortened to pot.

 

POWER AMPLIFIER  Supplies the audio signals to the loudspeakers.

 

POWER HANDLING  The maximum safe power for speakers.  But be aware that it's easier to damage speakers by using an underpowered amplifier being driven hard than it is by using too much power.

POWER OUTPUT  The amount of power, measured in Watts/RMS per channel delivered by an Amplifier to loudspeakers or a load.

 

PRE AMPLIFIER  The control section of an amplifier.  This is built into integrated amplifiers but can also be separate  and used with power amplifiers or with active speakers.  A pre-amplifier usually contains a Volume pot for the drive levels to the amps and switching for source signals.

 

PRO-LOGIC  Produced by DOLBY Labs for home theater systems, using four amplifier channels for Left, Right, Center and Rear (Ambient) speakers. 

 

PUSH PULL AMPLIFIER  SEE ALSO CLASS B

 

Q 

 

R

RDS  Radio Data System.   A data system on FM radio that carries data that allows RDS equipped tuners to display the names of stations, an d perform a range of station-seek and switching functions.  A system that is more useful for in-car use rather than for home use.  Only found in the UK, parts of Europe and possibly Japan?

 

RESISTANCE 

The simplest form of impedance. Resistance opposes the flow of current equallly at all frequencies in a wire, loudspeaker or other electrical device. The more resistance, the less current.

 

RESONANT FREQUENCY

Proportional to the square root of the product of mass and stiffness. (These factors are also found in the equation for Q.)

Speaker manufacturers do not always indicate the resonant frequencies of their speakers in their specifications. (Usually dealers will know.) Generally, the lowest the resonance the deeper the bass (assuming that everything else is all right with the speaker.)

Usually a speaker with low resonance is well made.

The smaller the box or the larger the woofer, the higher the resonant frequency. Therefore a fifteen inch woofer requires a huge box to keep its resonant frequency low enough.

 

RIGIDITY

An important quality in speaker components like woofer cones and tweeter domes, since the more rigid the radiator, the more it acts like a theoretical or ideal device.

 

RINGING

An uncontrolled resonance, generally in a small part of a tweeter or woofer that's loose and shouldn't be, or is allowed to vibrate uncontrolled by the voice coil. Generally, a sign that a speaker is not well-made.

 

 

S

SAMPLING RATE  How fast a digital recorder or player samples a signal.  CD, DCC and Minidisc use a rate of 44.1kHz - 44,100 samples per second - while DAT recorders offer a choice of either 48kHz, 44.1kHz or 32kHz.  A Digital-To-Analogue converter needs to be able to work with all three of these rates.  The sampling rate determines the highest frequency that the digital system can carry, when a digital signal of 44.1kHz is changed back to analogue, the highest frequency is roughly half of the sampling rate so in this instance it would be 22.05kHz.  Hence the development of higher sampling formats such as Pioneer's 96kHz system, for better treble extension.

 

SATELLITES

Very small speaker enclosures with only a tweeter or a mid-range and a tweeter. These are designed for high frequencies only and are usually combined with a bass unit, sub-woofer or other main speakers.

Satellites can be used as main speakers, when combined with a sub-woofer or bass unit or as rear channel speakers.

 

 

SHIELDING  Keeps a conductor or equipment away from interference.

 

SIGNAL-TO-NOISE-RATIO  Describes the difference between the level of the audio signal and the level of the unwanted noise.  The larger the figure in decibels (dB) the lower the noise will be.

 

SOFT DOME TWEETER

A dome tweeter made out of relatively soft material, which allows radiation from only a portion of the dome (mostly adjacent to the bond to the voice coil)

 

SPEAKER CONTROLS

Some loudspeakers have controls which allow the owner to modify their sound. Usually there's a knob to change tweeter response, and in three-way or four-way systems, a knob or knobs to change the intensity of midrange response.

The purpose of these controls is to permit the speakers to be "tuned" to the room in which they will perform and/or to the ear of the listener. Some individuals spend a great deal on speakers then fail to get maximum performance from them by neglecting to find the optimum settings for controls (a process which may take quite a bit of time and experimentation.)

There's no system so good that it can't be improved. Therefore minor adjustments to speaker and electronic component controls may easily create an improvement in overall sound. The listener should feel free to experiment until he arrives at the sound quality which suits both the environment and his own hearing. The ear, not some arbitrary ideal setting (e.g. flat controls) should be the ultimate test.

 

SPEAKER SPECIFICATIONS

Most specifications which are used to promote and sell loudspeaker are simply those which are easily made. The equipment used to produce them is easily obtained and easy to use. So, most specifications you may read about a piece of equipment are not generally very important to the performance of the unit. Every time someone invents a new piece of test equipment, one finds new specs getting into speaker literature.

FREQUENCY RESPONSE is a specification where there has been confusion for years. That's because there is no simple or agreed-upon way of measuring the frequency response of a speaker. Microphone placement, room size and shape, reflecting surfaces, etc. may vary and give immensely different specifications for the same speaker. For example, it's quite easy for frequency response specifications to go from +/- 2 dB to +/- 10 dB simply by repositioning the microphone, creating perfectly "accurate" yet completely different specifications for the same speaker.

Historically the meaning for frequency response has been "any audio output in that frequency". In these terms, a response curve reading 15 Hz to 25 KHz is completely meaningless because both these frequencies are beyond the range of human hearing.

Furthermore, they are both outside the range of the usual test equipment used by speaker manufacturers to test their products. This means that such specifications are either being made up by copywriters and engineers, or that they are judging by any kind of audio output. (For example, if you put 15 Hz into many speakers, you'll hear something. It won't be 15 Hz, but one of its harmonics: 30, 45, Hz etc.)

On-axis measurement of frequency response is also tricky. Lots of speakers have response up to about 16 KHz +/- 3 to 5 dB if the microphone is placed dead center in front of the speaker. That kind of measurement gives good specifications. However, anywhere but straight ahead the actual power output at the highest frequencies may be negligible compared to other frequencies. (See DIRECTIONALITY.)

CROSSOVER frequency specifications? Who cares? The usual reasons for including them: they're easy to specify and fill out some of the white space on the page.

A basic tenet of science is that measuring techniques inevitably affect the phenomenon being measured. A good example of this occurs in the field of amplifiers. For years amplifiers have been judged by an inexpensive piece of equipment to measure it. There are amplifiers which sound better with their high harmonic distortion than others with better specifications, but it's the ones with the best specs which sell best. In speakers, a new piece of equipment has just become available to measure phase distortion, and now all kinds of specifications relating to phase are appearing in the industry's literature; yet it's a relatively unimportant consideration. In this sense, the importance given to specs by reviewers may not be helping the public

 

 

SPEAKER WIRE

Audiophiles with extremely sensitive hearing claim that they can hear differences between various forms of speaker wire. Scientific evidence for this is very slight. Even straight wire has some inductance, and there is always at least some capacitance between two wires in proximity to each other. It turns out that there are some wires which have detectable reactance at audible frequencies and therefore to infer that there may be some audible effects.

There are many conjectures about how wire can cause a difference in sound, such as oxidation in the wire, magnetic eddy currents within thick wires, rectification between wire strands, and interference between high and low frequencies.

What is certainly true is that the thinner and longer the wire, the more resistance. Speakers usually have impedance of several ohms. In order that the resistance of the wire be small compared to that of the speaker, one half ohm would be too much. 

 

SPL

Sound Pressure Level is expressed in dB and is defined in terms of the practical hearing range of human hearing. For the human ear, silence is defined as 0 dB SPL. The threshold of pain for the human ear is at about 130 dB SPL. 

 

STANDING WAVE

An acoustic resonance of high Q, generally an annoying form of distortion, usually in the bass, caused by the shape and dimensions of the room in which music is being reproduced. When the distance between two parallel room surfaces is one fourth of the wave length of a given frequency, or an odd multiple of the wave length (three times, five times, etc.) the pressure of the reflected wave is in phase with the wave itself, creating a room resonance at that frequency.

On the other hand, if the distance between the two room surfaces is one half the wave length, or an integral multiple thereof, the pressure of the reflected wave is out of phase with the wave itself, creating a canceling at the frequency which is another form of distortion but a bit less noticeable.

Of the two types of distortion, the former is the greatest problem, because it tends to augment or complicate acoustic feedback.

Careful repositioning of speakers, careful repositioning of objects in the room (like furniture) and the use of sound-absorbing materials on room surfaces are the classic solutions to standing waves. The fewer parallel planes there are in the room's surfaces, the less likely that there will be standing waves, so that room acoustics are generally improved by angling a wall or two, and/or the ceiling, when the room is being planned.

Organ pipes are based on standing waves.

 

 

STEREO and STEREO EFFECT

 

If a click is heard by both ears at once, it will appear to be straight ahead or behind the listener. If the sound reaches one ear slightly sooner, the sound will seem to emanate from that side. 

This is the principal cause of stereo effect, a shift in timing or phase.

However, a change in volume in one ear will have a similar stereo effect. Because of studio mixing techniques, many stereo recordings use only this volume differential to convey stereo information, and overlook or ignore the primary information, timing. This stereo is not as complete, but is particularly common in pop recordings, where one track is recorded at a time and then added to the final tape.

At very low frequencies, however, phase information in two channels is almost nil because of the wavelength of the sounds. Conversely, at frequencies where wavelength comes close to the size of the space between the ears, (250-10,000Hz), the perception of directionality increases.

 

 

SUBWOOFER  A separate speaker enclosure (often with its own power amplifier) dedicated only to bass frequecies, e.g., from 15 - 150 Hz. The theory is that most stereo speaker systems lack one or two octaves of the deepest bass, and that this can be added with a separate speaker. Unfortunately many so-called sub-woofers are still missing one or two octaves of the deepest bass.

Sub-woofers are often configured as one monaural channel, on the assumption that low frequencies have very little stereo information.

 

T

TAPE LOOP  A pair of sockets found on an amplifier used for connecting the input and output signals used on recording equipment.

 

THIELE  

An Australian electrical engineer whose name has become quite famous in audio circles. Thiele's work was based on the fact that any loudspeaker system can be expressed in classic electronic symbols. He then applied filter theory (a special branch of electronic analysis) to speaker design.

The advantage of Thiele's work is that it makes it possible for the designer to avail himself of the immense body of statistics and research that has gone into electrical filter theory in order to obtain the desired frequency and phase response in a new design with minimum trial and error.

Thiele's theories have been taken up and popularized by Richard Small, who did a Ph.D. on Thiele's work.

Today's speaker designers often use filter theory, analyzing loudspeakers as analogous to electronic circuits. This approach is particularly useful for designs using either a port or a passive radiator, for Thiele's work is particularly applicable to the selective tuning of the port or radiator to achieve desired frequency response. Still, the Thiele approach is only one of several methods which may be used to arrive at the desired result.

 

 

THIELE-SMALL PARAMETERS

These are the values of the basic parts of the electronic circuit analogue proposed by THIELE and popularized by Small. They are related to the physical properties of a woofer, e.g. mass compliance, resonance, Q, Bl, etc. They are commonly circulated between manufacturers and design engineers because there are a number of cookbook recipes which use the Thiele -Small parameters for determining box size and port tuning. Computer programs are now common both for measuring the parameters and for designing the enclosures based on them.

 

 

THX  Developed by Lucas Film for the Star Wars film.  This is basically a set of standards for Dolby Pro-Logic equipment which guarantees a high quality home cinema sound.  Electronics with the THX approved stamp tend to be mainly American and very expensive to boot.  The real kicker is that outside of the US, no equipment can be THX approved so making a nonsense of it.

 

TONEARM  The device on which a turntable holds the cartridge.

 

TOROIDAL TRANSFORMER  Transformers bring down mains voltages top the levels required.  Toroidal transformers (doughnut shaped) get better stability and less flux leakage (magnetic radiation that can  interfere with other circuits).  These transformers are also known as Torus (meaning round).

 

TRANSDUCER  Any device which converts mechanical energy to electrical energy, or vice versa. Therefore, speakers, microphones, generators, alternators, motors, cartridges, etc. In speakers there are generally three types of transducers: dynamic, or conventional magnet and coil and paper cone; electrostatic, and piezo-electric effect.

In the dynamic type, sound comes from the movement of a coil in a magnetic field when current passes through it. In electrostatic, variations in voltage on two plates causes one plate to move in respect to the other (one plate effectively replaces the magnet of the dynamic speaker) transmitting a sound wave to the air in the room. In the piezo-electric effect, current causes a change in the shape of the material, a solid, causing it to vibrate and transmit sound waves to the air. (All these effects also work in the opposite direction.)

Transducers are particularly important in high fidelity because they are used in speakers, microphones, and cartridges, and they all have to be good for the sound to be good.

 

TRANSMISSION LINE 

One type of transmission line is a type of bass reflex system with the added characteristic of providing a long path for the rear wave to follow so that by the time it gets out of the enclosure it is in phase (in a certain frequency range) with the front wave. Not particularly useful, since this design offers neither the frequency range nor the efficiency of a tuned port. It is however appropriate for those who prefer a softer, well-damped bass.

A second type of transmission line, less common, uses a cabinet design which absorbs all the rear energy from the woofer, making it behave as if it were mounted in an infinite baffle.

 

TRANSIENTS  A term often used ambiguously. Specifically, transient response is the ability of a system to reproduce sudden changes, such as clicks or pops, especially at the beginnings of continuous sounds, rather than a steady waveform (sine wave).

In reality transient response is a reflection of frequency response. Pass a pulse through any system with a certain frequency response, and the accuracy of reproduction of a transient waveform will correspond to the limitations of the system's frequency response. A square wave can be used to indicate transient response. If there's a deficiency in high end response there will be a rounding of the square wave and a change in the vertical edge.

Though transient response is usually thought of as a high frequency function, there is also such thing as low frequency transient response. Failure to handle this results in a tilt of the horizontal section of the wave.

Some people confuse high Q with poor low frequency transient response, because drums seem to be muffled in a high Q system, and this can be erroneously labeled "poor low frequency transient response". Actually, poor low frequency transient response is of limited importance since the human ear does not usually recognize the absence of low frequency harmonics (or sub-harmonics).

 The Cannon blasts on 'Mercury Living Presence release of Tchaikovsky's 1812 Overture' has been the downfall of many amplifiers and speakers, such is its intensity. 

 

TREBLE  High Frequency signals.  When a speaker is described as having a 'Splashy' treble, it means that the sound is more like 'Tizzssshhh' rather than having a crisp sting.

 

TRIAMPING/TRIWIRING  Like biwirng and biamping but for three-way speakers.  Needs three runs of cables in triwiring and three stereo amps for triamping.

 

TUNED PORT/BASS REFLEX

A tuned port is simply a tube or opening allowing air from inside the speaker box to escape or enter. Note that the air in a tuned port has the property of acoustic mass. It moves in the port without being compressed, has inertia, and therefore has its own resonant frequency. The port is generally tuned (dimensioned) in the vicinity of the woofer's resonant frequency in order to augment bass output. A tuned port can be used either to increase efficiency or to increase frequency range, depending on the goals of the designer.

 

TWEETER  The speaker driver that handles the treble or high frequency component of the signal.

 

U 

 

V

VALVE  Amplifying device.  Electrodes in a glass vacuum enclosure.  Know also as Tubes.  Valved equipment produce a warm, almost seductive sound.

 

W

WATT  Unit of power.  More watts mean more power, but how loud a system sounds also depends on speaker sensitivity and room size.  See also PMPO.

 

WAVELENGTH  The length of a wave.  Sound at 50Hz in air has a wavelength of around 6.9 metres.  Inverse to frequency, waves are short at high frequencies and long at low frequencies. The corresponding range for 20 to 20,000 Hz is 50 feet to 1/2 inch. Wavelength is the distance from crest to crest, similar to ocean waves.

 

WHITE NOISE and PINK NOISE

NOISE is often used in testing speakers because it's easy to obtain. Also, a lot of companies like to use noise as a signal source when measuring specifications because it does not show up peaks in the frequency response as a pure tone would.

WHITE NOISE: noise in which there is equal energy per frequency division. (For example, the same amount of energy between 100 and 200 Hz as between 1100 and 1200). 

PINK NOISE has equal energy distributed logarithmically, for example, the same energy between 100 and 200 Hz as between 1000 and 2000. Pink noise corresponds fairly closely, on an average basis, to music. (More energy at low frequencies.) In listening tests with speakers, Pink noise is a better listening tool than White noise. In white noise there is a great exaggeration of treble. Surf is an excellent example of white noise.

High frequency sound is attenuated in air (particularly humid air) so that the closer you are to surf (white noise) the shriller it sounds. Even the humidity in your living room will to some degree influence the treble response of your speakers. On cold winter mornings, sound travels well, not just because the air is cold, thus dense, but also because of its dryness. (Very cold air rejects humidity.) Probably no-one will seriously suggest getting a dehumidifier for your living room in order to improve the high end response of your sound system. Still, acoustically speaking, it would help.

 

WOOFER  The large drive unit in a speaker which is used to produce bass frequencies.

 

WOW  Slow variations in speed of a record or tape deck, making sustained notes sound unsteady.

 

X 

 

Y 

 

Z

Z (see also Impedance)

 

Mick Evans 1999-2001

  [email protected]

[email protected]