adiabatic
Literally,
it means "not to pass through." In describing the
high-density foam used inside the HR824s, it means that internal
reflections within the cabinet are absorbed by the foam. In
physical terms, it means the mechanical energy of the sound
wave is converted into heat energy.
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AFL
An
acronym for After Fade Listen, which is another way of saying
post-fader solo function.
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assign
In
sound mixers, assign means to switch or route a signal to a
particular signal path or combination of signal paths.
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attenuate
To reduce or make quieter |
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aux
See
auxiliary.
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auxiliary
In
sound mixers, supplemental equipment or features that provide
additional capabilities to the basic system. Examples of auxiliary
equipment include: serial processors (equalizers, compressors,
limiters, gates) and parallel processors (reverberation and
delay). Most mixers have aux send buses and aux return inputs
to accommodate auxiliary equipment. Aux Send and Returns are
usually only used with parallel processors.
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balanced
In a classic balanced audio circuit, the two legs of the
circuit (+ and - ) are isolated from the circuit ground by exactly
the same impedance. Additionally, each leg may carry the signal
at exactly the same level but with opposite polarity with respect
to ground. In some balanced circuits, only one leg actually
carries the signal but both legs exhibit the same impedance
characteristics with respect to ground. Balanced input circuits
can offer excellent rejection of common-mode noise induced into
the line and also make proper (no ground loops) system grounding
easier. Usually terminated with 1/4" TRS or XLR connectors.
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bandwidth
The
band of frequencies that pass through a device with a loss of
less than 3dB, expressed in Hertz or in musical octaves. Also
see Q.
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bus
An
electrical connection common to three or more circuits. In mixer
design, a bus usually carries signals from a number of inputs
to a mixing amplifier, just like a city bus carries people from
a number of neighborhoods to their jobs.
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Cannon
A
manufacturer of electrical connectors who first popularized
the three-pin connector now used universally for balanced microphone
connections. In sound work, a Cannon connector is taken to mean
a Cannon XLR-3 mic connector or any compatible connector.
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cardioid
Means
heart-shaped. In sound work, cardioid refers to the shape of
the sensitivity pattern of some directional microphones.
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channel
A
functional path in an audio circuit: an input channel, an output
channel, a recording channel, the left channel and so on.
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channel
strip
The
physical representation of an audio channel on the front panel
of a mixer; usually a long, vertical strip of controls. |
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chorusing
An
effect available in some digital delay effects units and reverbs.
Chorusing involves a number of moving delays and pitch shifting,
usually panned across a stereo field. Depending on how used,
it can be lovely or grotesque.
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clipping
A
cause of severe audio distortion that is the result of excessive
gain requiring the peaks of the audio signal to rise above the
capabilities of the amplifier circuit. Seen on an oscilloscope,
the audio peaks appear clipped off. To avoid distortion, reduce
the system gain in or before the gain stage in which the clipping
occurs. See also headroom.
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condenser
Another term for the electronic component generally known
as a capacitor. In audio, condenser usually refers to a type
of microphone that uses a capacitor as the sound pickup element.
Condenser microphones require electrical power to run internal
amplifiers and maintain an electrical charge on the capacitor.
They are typically powered by internal batteries or "phantom
power" supplied by an external source, such as a mixing
console.
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console
A
term for a sound mixer, usually a large desk-like mixer.
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crest
factor
The ratio of the peak value to the RMS value. Musical signals
can have peaks many times higher than the RMS value. The larger
the transient peaks, the larger the crest factor.
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cueing
In
broadcast, stage and post-production work, to "cue up"
a sound source (a record, a sound effect on a CD, a song on
a tape) means to get it ready for playback by making sure you
are in the right position on the "cue," making sure
the level and EQ are all set properly. This requires a special
monitoring circuit that only the mixing engineer hears. It does
not go out on the air or to the main mixing buses. This "cueing"
circuit is the same as pre-fader (PFL) solo on a Mackie mixer,
and often the terms are interchangeable.
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damping
Damping
factor is a number that represents the ratio of the impedance
of the load to the output impedance of the amplifier. In practical
terms, it is a measure of how well the amplifier can control
the movement of a speaker’s cone. The greater the damping
factor, the better its ability to control the cone’s movement.
A low damping factor (high amplifier output impedance) allows
a woofer to continue to move after the signal stops, resulting
in an indistinct and mushy low frequency response. A high damping
factor (200 or above) provides excellent control over low frequency
woofers and produces a tight, clean bass.
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dB
See
decibel.
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dBA
Sound
Pressure Level (SPL) measured with an "A" weighting
filter.
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dBm
A
unit of measurement of audio signal level in an electrical circuit,
expressed in decibels referenced to 1 milliwatt. The "m"
in dBm stands for "milliwatt." In a circuit with an
impedance of 600 ohms, this reference (0dBm) corresponds to
a signal voltage of 0.775 VRMS (because 0.775 V across 600 ohms
equals 1mw).
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dBu
A
unit of measurement of audio signal level in an electrical circuit,
expressed in decibels referenced to 0.775 VRMS into any impedance.
Commonly used to describe signal levels within a modern audio
system.
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dBv
A
unit of measurement equal to the dBu but no longer in use. It
was too easy to confuse a dBv with a dBV, to which it is not
equivalent.
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dBV
A
unit of measurement of audio signal level in an electrical circuit,
expressed in decibels referenced to 1 VRMS across any impedance.
Commonly used to describe signal levels in consumer equipment.
To convert dBV to dBu, add 2.2dB.
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decibel
(dB)
The
dB is a ratio of quantities measured in similar terms using
a logarithmic scale. Many audio system parameters measure over
such a large range of values that the dB is used to simplify
the numbers. A ratio of 1000V:1V=60dB. When one of the terms
in the ratio is an agreed upon standard value such as 0.775V,
1V or 1mw, the ratio becomes an absolute value, i.e., +4dBu,
-10dBV or 0dBm.
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delay
In
sound work, delay usually refers to an electronic circuit or
effects unit whose purpose it is to delay the audio signal for
some short period of time. Delay can refer to one short repeat,
a series of repeats or the complex interactions of delay used
in chorusing or reverb. When delayed signals are mixed back
with the original sound, a great number of audio effects can
be generated, including phasing and flanging, doubling, Haas-effect
positioning, slap or slapback, echo, regenerative echo, chorusing
and hall-like reverberation. Signal time delay is central to
many audio effects units.
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detent
A
point of slight physical resistance (a click-stop) in the travel
of a knob or slide control, used in Mackie mixers to indicate
unity gain.
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diffraction
The
bending of sound waves around an obstacle (Huygens Principle).
The longer the wavelength in comparison to the obstacle, the
more the wave will diffract around it.
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dipping
The
opposite of peaking, of course. A dip is an EQ curve that looks
like a valley, or a dip. Dipping with an equalizer reduces a
band of frequencies. See guacamole.
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doubling
A
delay effect, where the original signal is mixed with a medium
(20 to 50 msec) delay. When used carefully, this effect can
simulate double-tracking (recording a voice or instrument twice).
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dry
Usually
means without reverberation, or without some other applied effect
like delay or chorusing. Dry is not wet, i.e. totally unaffected.
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duty
cycle
The
ratio of pulse width to total cycle time.
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dynamic
In
sound work, dynamic refers to the class of microphones that
generate electrical signals by the movement of a coil in a magnetic
field. Dynamic microphones are rugged, relatively inexpensive,
capable of very good performance and do not require external
power.
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dynamic
range
The
range between the maximum and minimum sound levels that a sound
system can handle. It is usually expressed in decibels as the
difference between the level at peak clipping and the level
of the noise floor.
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echo
The
reflection of sound from a surface such as a wall or a floor.
Reverberation and echo are terms that can be used interchangeably,
but in audio parlance a distinction is usually made: echo is
considered to be a distinct, recognizable repetition (or series
of repetitions) of a word, note, phrase or sound, whereas reverberation
is a diffuse, continuously smooth decay of sound. Echo and reverberation
can be added in sound mixing by sending the original sound to
an electronic (or electronic/acoustic) system that mimics natural
echoes, and then some. The added echo is returned to the blend
through additional mixer inputs. Highly echoic rooms are called
live; rooms with very little echo are called dead. A sound source
without added echo is dry; one with reverb or echo added is
wet.
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effects
devices
External
signal processors used to add reverb, delay, spatial or psychoacoustic
effects to an audio signal. An effects processor may be used
as an insert processor (serial) on a particular input or subgroup,
or it may be used via the aux send/return system(parallel).
See also echo, reverb.
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EIN
Equivalent
Input Noise. Specification that helps measure the "quietness"
of a gain stage by deriving the equivalent input noise voltage
necessary to obtain a given preamp's output noise. Typically
ranges from -125 to -129.5 dBm.
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EMI
Electro
Magnetic Interference. This refers to current induced into the
signal path as a result of an external magnetic field. In audio
systems, this is usually manifested as a 60Hz or 120Hz hum or
buzz (50Hz or 100Hz in 50Hz systems). The source of this noise
can be from a ground loop or from the signal wire coming too
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EQ
See
equalization.
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EQ
curve
A
graph of the response of an equalizer, with frequency on the
x (horizontal) axis and amplitude (level) on the y (vertical)
axis. Equalizer types and effects are often named after the
shape of the graphed response curve, such as peak, dip, shelf,
notch, knee and so on.
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equalization
Equalization
(EQ) refers to purposefully changing the frequency response
of a circuit, sometimes to correct for previous unequal response
(hence the term, equalization), and more often to add or subtract
level at certain frequencies for sound enhancement, to remove
extraneous sounds, or to create completely new and different
sounds.
Bass and treble controls on your stereo are EQ; so are the units
called parametrics and graphics and notch filters.
A lot of how we refer to equalization has to do with what a
graph of the frequency response would look like. A flat response
(no EQ) is a straight line; a peak looks like a hill, a dip
is a valley, a notch is a really skinny valley, and a shelf
looks like a plateau (or a shelf). The slope is the grade of
the hill on the graph.
Graphic equalizers have enough frequency slider controls to
form a graph of the EQ right on the front panel. Parametric
EQs let you vary several EQ parameters at once. A filter is
simply a form of equalizer that allows certain frequencies through
unmolested while reducing or eliminating other frequencies.
Aside from the level controls, EQs are probably the second most
powerful controls on any mixer (no, the power switch doesn’t
count!).
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fader
Another
name for an audio level control. Today, the term refers to a
straight-line slide control rather than a rotary control.
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family
of curves
A
composite graph showing on one chart several examples of possible
EQ curves for a given equalizer or equalizer section.
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filter
A
simple equalizer designed to remove certain ranges of frequencies.
A low-cut filter (also called a high-pass filter) reduces or
eliminates frequencies below its cutoff frequency. There are
also high-cut (low-pass) filters, bandpass filters, which cut
both high and low frequencies but leave a band of frequencies
in the middle untouched, and notch filters, which remove a narrow
band but leave the high and low frequencies alone.
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flanging
A
term for phasing. Before digital delay effects units, phasing
could be accomplished by playing two tape machines in synchronization,
then delaying one slightly by rubbing a finger on the reel flange.
Get it?
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FOH
An
acronym for Front Of House. See house
and main house speakers.
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frequency
The
number of times an event repeats itself in a given period. Sound
waves and the electrical signals that represent sound waves
in an audio circuit have repetitive patterns that range from
a frequency of about 20 repetitions per second to about 20,000
repetitions per second. Sound is the vibration or combination
of vibrations in this range of 20 to 20,000 repetitions per
second, which gives us the sensation of pitch, harmonics, tone
and overtones. Frequency is measured in units called Hertz (Hz).
One Hertz is one repetition or cycle per second.
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gain
The
measure of how much a circuit amplifies a signal. Gain may be
stated as a ratio of input to output values, such as a voltage
gain of 4, or a power gain of 1.5, or it can be expressed in
decibels, such as a line amplifier with a gain of 10dB.
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guacamole
Just
kidding, dip.
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gain
stage
An
amplification point in a signal path, either within a system
or a single device. Overall system gain is distributed between
the various gain stages.
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graphic
EQ
A
graphic equalizer uses slide pots for its boost/cut controls,
with its frequencies evenly spaced through the audio spectrum.
In a perfect world, a line drawn through the centers of the
control shafts would form a graph of the frequency response
curve. Get it? Or, the positions of the slide pots give a graphic
representation of boost or cut levels across the frequency spectrum.
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ground
Also
called earth. Ground is defined as the point of zero voltage
in a circuit or system, the reference point from which all other
voltages are measured. In electrical systems, ground connections
are used for safety purposes, to keep equipment chassis and
controls at zero voltage and to provide a safe path for errant
currents. This is called a safety ground.
Maintaining a good safety ground is always essential to prevent
electrical shock. Follow manufacturer’s suggestions and
good electrical practices to ensure a safely grounded system.
Never remove or disable the grounding pin on the power cord.
In computer and audio equipment, tiny currents and voltages
can cause noise in the circuits and hamper operation. In addition
to providing safety, ground provisions in these situations serve
to minimize the pickup, detection and distribution of these
tiny noise signals. This type of ground is often called technical
ground.
Quality audio equipment is designed to maintain a good technical
ground and also operate safely with a good safety ground. If
you have noise in your system due to technical grounding problems,
check your manual for wiring tips or call technical support.
Never disable the safety ground to reduce noise problems.
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ground
loop
A
ground loop occurs when the technical ground within an audio
system is connected to the safety ground at more than one place.
Two or more connections will allow tiny currents to flow in
the loops created, possibly inducing noise (hum) in the audio
system. If you have noise in your system due to ground loops,
check your manual for wiring tips or call technical support.
Never disable the safety ground to reduce noise problems.
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Haas
effect
A
psychoacoustic effect in which the time of arrival of a sound
to the left and right ears affects our perception of direction.
If a signal is presented to both ears at the same time at the
same volume, it appears to be directly in front of us. But if
the signal to one ear, still at the same volume, is delayed
slightly (0 to 5 msec), the sound appears to be coming from
the earlier (non-delayed) side.
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headroom
The
difference between nominal operating level and peak clipping
in an audio system. For example, a mixer operating with a nominal
line level of +4dBu and a maximum output level of +22dBu has
18dB of headroom. Plenty of room for surprise peaks.
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Hertz
The
unit of measure for frequency of oscillation, equal to 1 cycle
per second. Abbreviated Hz. KHz is pronounced "kay-Hertz"
and is an abbreviation for kilohertz, or 1000 Hertz.
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house
In
Sound Reinforcement parlance, "house" refers to the
systems (and even persons) responsible for the primary sound
reinforcement in a given hall, building, arena or "house."
Hence we have the house mixer or house engineer, the house mix,
the house mix amps, the main house speakers and so on.
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Hz
See
Hertz.
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impedance
The
A.C. resistance/capacitance/inductance in an electrical circuit,
measured in ohms. In audio circuits (and other AC circuits)
the impedance in ohms can often be much different from the circuit
resistance as measured by a DC ohmmeter.
Maintaining proper circuit impedance relationships is important
to avoid distortion and minimize added noise. Mackie input and
output impedances are set to work well with the vast majority
of audio equipment.
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input
module
A
holdover from the days when the only way that real consoles
were built was in modular fashion, one channel per module. See
channel strip.
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knee
A
knee is a sharp bend in an EQ response curve not unlike the
sharp bend in your leg. Also used in describing dynamics processors. |
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level
Another
word for signal voltage, power, strength or volume. Audio signals
are sometimes classified according to their level. Commonly
used levels are: microphone level (-40dBu or lower), instrument
level (-20 to -10dBu), and line level (-10 to +30dBu).
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line
level
A
signal whose level falls between -10dBu and +30dBu. |
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