- Home Theater FAQ's and Information
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Glossary and Terms A Thru F
- Having to do with sound that can be heard by the ears.
The quality of a surface or substance to take in the soundwave
and not reflect it or pass it through, or an instance of this.
- A type of speaker system in which the air in the enclosure acts as
a spring that shapes the response of the driver/box system, and also
works as the dominant restoring force on the driver cone.
Acoustic suspension designs have lower sensitivity than ported
designs (see below) and therefore need additional amplifier power to
achieve the same sound pressure level as an otherwise equivalent
ported box. Acoustic suspension designs, though, are able to play
lower in the frequency spectrum at the same volume, and provide
tighter and better-defined sound. Not all sealed speakers are
acoustic suspension designs.
- An abbreviation
of analog to digital conversion (the conversion of a quantity that
has continuous changes into numbers that approximate those changes),
or Analog to Digital Converter.
- An abbreviation of
Audio Engineering Society.
- A standard for sending and receiving digital audio adopted by the
Audio Engineering Society and the European Broadcast Union.
- A term with the same meaning as the termreverberant field (the
area away from the sound source where the reverberation is louder
than the direct sound.
Amp - 1) An
abbreviation of the term amplifier (A device which increases the
level of an electrical signal. 2) An abbreviation of Ampere (the
unit of current). 3) An abbreviation of amplitude (the height of a
waveform above or below the zero line).
Ampere - The unit of current,
(Amperes, Amps, symbol A or I) - units of measurement of electrical
current. Current is the flow of electrical charge carriers,
usually electrons, through an electronic circuit. Using the analogy
of water flowing through a pipe, current is the equivalent of the
flow of water moving through it.
- An increasing of signal strength.
- A device which
increases the amplitute (level) of an electrical signal (making it
- A making smaller:
reduction of electrical or acoustic signal strength.
- Most often referring to electrical signals resulting from the
sound pressure wave being converted into electrical energy.
Baffles - Sound absorbing panels
used to prevent sound waves from entering or leaving a certain
Balance Control - A
control on a stereo amplifier that when moved clockwise will make
the right channel
louder (and the left channel softer) and will do the reverse when
- 1) Having a pleasing
amount of low frequencies compared to mid-range frequencies and high
frequencies. 2) Having a pleasing mixture of the various instrument
levels in an audio recording. 3) Having a fairly equal level in each
of the stereo channels. 4) A method of interconnecting electronic
gear using three-conductor cables.
- When applied to parts of the frequency spectrum, bandwidth is the
range of difference between the highest and lowest frequencies
contained in a signal. Audio bandwidth is typically listed as 20 Hz
to 20 kHz, or cycles per second.
When applied to audio
equipment, bandwidth indicates the range over which it will
reproduce audio frequencies without attenuation. The bandwidth
of some commonly used media that operate in or near the audible
||5 Hz-22 kHz
||0 Hz-100 kHz
||0 Hz-96 kHz
In telecommunications, the term
bandwidth indicates capacity of a communications channel.
Analog communications bandwidth is measured in cycles per second, or
Hertz (Hz); digital communications, in kilobytes per second (kbs) of
data transfer. Analog telephone channels may have a bandwidth
of 4,000 Hz, while a digitally encoded telephone channels might
offer a bandwidth of 64 kbs.
Bass reflex speaker
- a type of vented speaker enclosure in which the mass and spring
characteristics of air in the vent (or port) help determine the low
frequency response of the driver/box system. Above a certain
frequency, determined by driver characteristics and the length of
the port, the driver and the air in the port work in phase to
produce a sound pressure level higher than that of a similarly sized
sealed enclosure. Below that frequency, the port and the
driver work against each other, out of phase, so output decreases
rapidly. The resonant characteristics of port and driver combine to
produce a different sound quality different than that of a sealed
A technique that uses two amplifiers to drive one loudspeaker. One
amplifier powers the midrange/tweeter section; the other powers the
woofer. An active crossover placed between the preamp and
power amps selects the high and low frequencies to send to their
respective amplifiers. This setup is particularly useful when
different levels are required for the woofer and
midrange/tweeter. A speaker must have two sets of connecting
terminals to use this method.
- A speaker which radiates sound primarily in opposite directions,
yet in phase, so as to diffuse the soundstage and offer a sense of
width. Bipole speakers are almost always designed with two drivers,
wired in phase, on opposite faces of a cabinet.
- A wiring technique that employs two runs of wire from amplifier
output terminals to speaker: one for the woofers; another for the
midrange/tweeter drivers. The speaker must have two separate sets of
terminals to use this wiring method. Compared to biamping,
biwiring tends to be subtle in sonic difference, requiring listening
sophistication to discern any qualitative change.
- To increase gain, especially to increase gain at specific
frequencies with an equalizer.
Frequency - The frequency of the
audio signal that is boosted or attenuated most by an equalizer with
a peak equalization curve.
A single path that an audio signal travels or can travel through a
device from an input to an output.
Classes of Amplifiers -
Amplifier classifications describe the methods by which they amplify
signals. The most common classes are Class A, Class B, and
amplifiers keep output stages on at all times, which minimizes
distortion but uses significant amounts of power.
amplifiers keep output stages off until a signal appears.
This cuts power use dramatically, but introduces distortion during
the stages turn-on phases.
amplifiers use a positive/negative device to shut off its outputs
nearly entirely, except for running a small bias current, when not
needed. It does this by almost completely turning off
positive polarity output off during negative signal cycles, and
negative output stages off when the signal is positive.
These amplifiers provide a
compromise between the sound quality of class A and the efficiency
of class B, offering lower distortion than the latter and less power
and heat loss than the former. This is the reason that the majority
of audio amplifiers are class AB.
amplifiers use the basic class AB design, but add other devices to
control power use. They do this by one of two methods. One
is to connect a single class AB output stage to two power supply
rails by a diode or transistor switch which only connects the
lower supply voltage unless large signal peaks occur, at which
point it switches to the higher rails. The other approach
uses two class AB output stages, each connected to a different
power supply voltage, with the magnitude of the input signal
determining the signal path. Either approach improves efficiency
enough to yield significantly more power for a given size and
weight, or less size and weight for a given amount of power.
(in amplifiers) - A distortion of the audio signal that occurs when
an amplifier reaches the limit of its power output and attempts to
increase the output level further by roughly clipping off the tops
and bottoms of waveforms. The sound of clipped waveforms is
hard and edgy, and have a much higher percentage of high frequency
energy than unclipped signals. This energy, being significantly high
frequency, gets routed straight to the tweeters, which have very
small voice coils that can't handle as much power as a larger woofer
voice coil, and can thus be easily burned out by clipped
signals. Since lack of sufficient amplifier power to drive
signals causes clipping, you are more likely to damage a tweeter
with a lower power amplifier than a higher power amplifier.
- Two-conductor cable consisting of one conductor surrounded by a
a method of treating information in such a way as to reduce its
total output. In analog audio, compression means squashing
down the peaks in audio output signals. In digital audio,
compression means encoding digital information to reduce the total
size of the data stream by eliminating information considered to be
redundant, unnecessary or at least not critical.
Corner Frequency - Same
as Cut-Off Frequency (the highest or lowest frequency in the pass
band of a filter
Critical Distance -
The point a distance away from the sound source where the direct
sound and the reverberant sound are equal in volume.
(Crossover Network) - A set of filters that
"split" the audio signal into two or more bands (two or
more signals, each of which have only some of the frequencies
- The frequency that is the outer limit of one of the bands of
Crosstalk - Leakage of an
audio signal into a channel that it's not intended to be in, from an
adjacent or nearby channel.
Current - The amount of electron
charge passing a point in a conductor per unit of time.
(Turnover Frequency) - 1) The highest or lowest frequency in
the pass band of a filter. 2) The highest or lowest frequency passed
by an audio device (the cut-off frequency is usually considered to
be the first frequency to be 3 dB lower than a reference frequency
in the middle of the bandwidth of the device)
Cycle - An alternation of a
waveform which begins at a point, passes through the zero line, and
ends at a point with the same value and moving in the same direction
as the starting point.
Cycles Per Second - A
unit used in the measure of frequency, equivalent to Hertz. Cycles
Per Second is an outdated term replaced by Hertz in 1948.
Chain -A hook
up of several devices where the audio signal has to pass through one
device to reach the second device and through the second device to
reach the third device.
DAT - An abbreviation of Digital
Audio Tape and a standard format for recording digital audio on
specially designed small cassette tapes.
dB - An abbreviation of the term Decibel, a
unit used in comparing signal strengths.
dBm - 1) Decibels of audio power
present compared to one milliwatt of power in a 600 ohm load. 2)
Very incorrectly and too commonly used to designate the reference
voltage of .775 volts of audio signal strength regardless of
dBu (dBv) -
The audio voltage present compared in dB to the level of .775 volts
of audio voltage in any impedance.
dBx - A
Manufacturer (brand) of noise reduction systems, dynamic processing
equipment and other audio gear.
Abbreviation of the term Direct Current (electric current flowing in
one direction only). Dead - 1) Referring to an
acoustically absorbent area or space. 2) A slang term for broken.
- 1) The rate of reduction of the audio signal generated in
synthesizers from the peak level to sustain level (see the term
ADSR). 2) The fade out of the reverberation of a sound
- The unit by which amplitude is measured. Decibel
measurements occur along a logarithmic scale in which each 10 dB
increase represents a tenfold increase in signal amplitude, while
each 10 dB reduction represents a tenfold reduction. The original
unit of measurement was the Bel, a ten times larger measurement (ie,
one Bel = ten dB). As electronic equipment improved, however, its
one-tenth-size relative, the decibel, came to be the standard unit.
The dB scale is useful in measuring changes in systems which our
nervous systems perceive in logarithmic ways, such as sound. The
most common use of the decibel is in measuring sound pressure level.
- The quality of a sound that allows it to be
distinguished from other sounds.
Degauss - A term with the same
meaning as Demagnetize (to remove the magnetism from).
Literally "Of Numbers"
Digital Delay - A delay
line or delay effects unit that converts the audio signal into a
digital audio signal, delays it, and converts it back to an analog
audio signal before sending it out of the unit.
Digital Interface Format (DIF)
- A specification of the number of bits, what the individual
bits mean, the voltage, and type of connector for digital audio
Digital Signal Processing
- Any signal processing done after an analog audio signal has been
converted into digital audio.
Digital To Analog
Converter - A device to change digital data numbers that
make up the digital audio into discrete voltage levels that
approximate the original analog audio waveform.
- To reduce the level of signals in a specific band of audio
- A speaker which radiates sound primarily in opposite directions,
180 degrees out of phase, This creates a null, or area with no
sound, to the sides of the speaker. Such designs are engineered by
using drivers wired out of phase, or by using both sides of a flat
Dipole speakers are most
commonly used as surround channel speakers IN older multi-channel
systems. They create a spacious sound field that makes it difficult
to tell the exact location of sound sources, which is useful in
creating the effect of being in a larger space.
- Separate, with no predetermined interaction between elements. In
electronics, the term refers to a design that uses individual parts
rather than an integrated circuit. In audio equipment, it means a
system made up of separate, single-function components rather than
combination equipment. And In multi-channel audio
systems, it indicates a system in which the signals on
individual channels are uniquely different from each other.
- The name of a manufacturer (and a trademark) of noise
reduction systems and other audio systems, to improve performance
and fidelity of audio recording, playback, and transmission.
- A small, protruding hemi-spherical driver which reproduces high
frequencies. Speakers using dome tweeters offer wider high-end
dispersion and smooth frequency response.
Effect - A change in frequency of a delayed signal
caused by the delay time changing while the cycle is being formed.
(Subwoofer, Woofer, Midrange, Tweeter) - The individual component of
a loudspeaker system that converts electrical energy into sound
energy. Tweeters, midranges, woofers, and subwoofers are all
examples of drivers, and all are technically known as transducers;
ie, devices which transform one type of energy into another.
All are made up of a linear magnetic motor and a piston; the piston,
in this case, being the part that drives air -- in most cases, a
cone or dome.
named for the low tones that it reproduces, is used for low
frequency reproduction. It's usually the largest driver on a
speaker, has the widest surround mounting, and creates long bass
wavelengths by displacing large volumes of air. At the
lowest frequencies, its movement is often dramatically
visible. Subwoofers are woofers placed in separate cabinets
for the sake of driver size (when all other factors are equal,
larger equals extended lower range) and placement flexibility.
The Midrange driver, used for
mid frequency reproduction in three-way speakers, tends to be
smaller than the woofer, and a bit thinner in material so that it
has the flexibility to reproduce higher frequencies.
which handles the high frequency reproduction, is the smallest of
a speakers drivers, and is made of the thinnest and most delicate
material so that it can respond the most quickly. It is
usually a small cone or dome; in rare cases, it takes the form of
- 1) Having no
reverberation or ambience. 2) More loosely used to describe an audio
signal without any signal processing.
- An abbreviation for Digital Signal Processing (Any signal
processing done after an analog audio signal has been convened into
- A DVD formatted disc that contains between two and six high
quality channels of audio material. DVD-A, as it's known,
doesn't use data compression (unlike like Dolby Digital and DTS,
both of which do) that could result in loss of signal detail. To
play back most DVD Audio discs, a player capable of playing this
format; ie, displaying the DVD Audio logo, is required. Some
DVD-A discs, though, also contain DTS or Dolby Digital tracks, and
can be played on any DVD player. The DVD-A format, however,
offers a 24 bit wordlength and 96 Kb clock rate, which makes its
resolution the highest of any common digital audio format.
Processing (Dynamic Signal
Processing) - An automatic change in level (or gain) to
change the level relationship of the loudest audio to the softest
The amount of fluctuation in level of an audio signal
-The difference between the loudest and the softest sounds either
contained in a piece of musical or other audio material. In
reproducing audio material, it means the range that can be
reproduced by a piece of audio equipment or audio format without
distortion. This ratio is expressed in dB.
Typical dynamic range for
Cassette 65 dB
CD 96 dB
SACD 120 dB
DVD Audio 144 dB
- The British version of the term Ground (In electronics, a place
that has zero volts).
Efficiency - the ratio of electrical energy delivered
into a device to the electrical energy it outputs. With respect to
audio amplifiers, it is the ratio of the power going into the unit
to the power being delivered out to the speakers. The higher
the number, which is expressed as a percentage, the more efficient
the device is, and the lower the amount of energy loss, mostly in
the form of heat. A perfectly efficient audio device would
have a hypothetical efficiency rating of 100%.
Electric Current -
A more formal term meaning the same as the term Current (the amount
of electron charge passing a point in a conductor per unit of time).
- Electrical current (the amount of electron charge passing a point
in a conductor per unit of time) or voltage (the force pushing
electrons to obtain electrical current).
Field - Magnetic energy put out because of
current traveling through a conductor.
or Pick Up - The generation of electrical signal in a
conductor moving in a magnetic field or being close to a changing
Theory - A statement of the principles
behind electromagnetic induction: When a conductor cuts magnetic
lines of force, current is induced in that conductor.
- 1) How a sound or audio signal varies in intensity over a time
span. 2) How a control voltage varies in level over time controlling
a parameter of something.
- Any time the amplitude of audio signals at specific set of
frequencies are increased or decreased more than the signals at
other audio frequencies.
Equipment Rack - A
cabinet with rails (or free standing rails) that have holes to
accept screws at standard spaces and used to house outboard gear.
1) A gradual reduction of the level of the audio signal. 2) A
gradual change of level from one pre-set level to another.
A control to control the gain of a channel on the console, thereby
determining the level of the signal in that channel.
Far Field -
The area from 3 feet away from the sound source up to the critical
Having more than a normal amount of signal strength at low
frequencies or having more sound than normal (by use of compression
To send an audio or control signal to.
1) A device that removes signals with frequencies above or below a
certain point called the cut-off frequency. 2) An equalizer section,
used in this sense because filters are used with other components to
give an equalizer its frequency response characteristics. 3) The
action of removing signals of some frequencies and leaving the rest.
4) A mechanical device to smooth out speed variations in tape
machines called a Scrape Flutter Filter- more usually called a
Scrape Flutter Idler.
- 1) An alternate tam meaning Range (a limit on the amount the
signal is reduced when the input signal is low by an expander or
gate). 2) A shortening of the term Noise Floor (the level of the
(Hz) - Rate of recurrence of oscillation, measured in cycles per
second (cps), and expressed in units known as Hertz (Hz). A 1
Hz frequency is a signal that completes one entire cycle of
oscillation in one second; a 100 Hz frequency completes a
hundred. With cycles exceeding 1000 a second, we instead use
the unit kilohertz, or kHz; a 15,000 cycle-per-second tone is
referred to as 15 kHz. Human sense of pitch is related to frequency;
usually we hear frequencies with few cycles per second as low, and
those more as higher. We also hear frequencies in simple
arithmetical relation to each other as pleasant. For instance,
all known human musical scales begin to repeat at the point of the
octave, whose upper and lower tones differ in Hz by exactly 2:1.
In pure engineering terms,
separate from where engineers and designers might set the crossover
points in speaker systems, we divide the frequency range into three
categories: low, mid and high.
is usually defined as the range from 20 to 100 Hz. Because
they cycle slowly, relative to mid and high frequencies, they have
longer wavelengths in air. These long length waveforms easily
diffract around smaller objects, making their way around any
barriers of less size. We tend to perceive low frequencies
as omni directional.
is usually held to occupy the range from 100 to 2,000 Hz.
This is the range in which most basic instrumental and vocal tones
occur and in which human hearing is the most sensitive. Mid
frequency sounds and tones, with shorter wavelengths, are more
easily absorbed by medium sized obstacles, and less likely to be
clearly discernible around corners or through barriers.
is usually considered to be in the range from 2,000 to 20,000
Hz. These frequencies, which often arise from smaller
sources -- a constricted throat, a small finger cymbal, the tiny
contact point between a fingernail and a chalkboard -- are also
best reproduced by small speakers. Their rapid cycle time
gives them very short wavelengths which are easily absorbed by
objects -- such as carpet or furniture -- whose thickness is
greater than their own cycle lengths. For this reason, they
usually cannot make their ways around obstacles or corners unless
strongly reflected by hard surfaces. They are, ultimately,
the most fragile of the frequencies -- easy to lose in recording
and mixing, and requiring quality components and placement care to
Human hearing, which perceives
all three of these ranges, is commonly held to range from 20 Hz to
20,000 Hz, although a few of us can hear higher or lower, and most
of us have less than that full range by adulthood.
- The cycles-per-second span over which any object can naturally
emit a sound is also known as the objects frequency range. Some
examples of fundamental frequency range for common voices and
Voice: ~300 Hz-1000 Hz
Tenor Voice: ~150 Hz-500 Hz
Bass Voice: ~90 Hz-300 Hz
Piano: ~30 Hz-4 kHz
Pipe Organ: ~17 Hz-8 kHz
Guitar: ~75 Hz-700 Hz
Trumpet: ~180 Hz-900 Hz
- The frequency above or below which audio equipment ceases to
function with full efficiency, either due to inherent limitation or
deliberate design. Typically, cutoff frequency specifications are
assigned to the point at which response drops by 3 dB relative to
full output, and continues to fall the further one measures in that
Response - How sensitive an electronic device (mic,
amplifier, speaker, etc.) is to various frequencies; often
communicated with a graph.
A quality of the sound of having all frequencies present, especially
the low frequencies.
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