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Glossary of PA Terms - F |
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The glossary pages provide definitions for over 1900 PA-related terms. If you can't find the term you are looking for, or would like any of the existing definitions to be expanded, please email me − likewise of course if you find any errors in the links etc. Use of this information is conditional upon acceptance of the Disclaimer on the PAforMusic home page.
F-hole * Fade down * Fade out * Fade up * Fader * Farad * Fault protection * FCC * Feed * Feedback * Feedback destroyer * Female * Ferrofluid * FET * FFT * Fibre-optic * Fidelity * Field * Field sync * Fifth * Fifth-order * Figure-of-8 cable * Figure-of-8 microphone * Fill * Filter * Finalise * FIR * FireWire * First generation * First-order * Fixture * Flanger * Flanges * Flat * Fletcher-Munson curves * Flight case * Float * Float switch * Floating * Floor * Floor monitor * Floor tom * Fluff * Fly * Flyware * FM * FOH * FOH engineer * FOH mixer * Foldback * Folded horn * Follow-spot * Foot drum * Forced cooling * Formant * Format * Fourier analysis * Fourth-order * Frame * Free field * Frequency * Frequency agile * Frequency modulation * Frequency response * Frequency shifter * Frequency spectrum * Fresnel * Fret buzz * Front end * Front-fill * Front-loaded * Front-of-house * Frontline * FS * Full-duplex * Full normalling * Full range * Full scale * Full space * Fully normalled * Fully parametric equaliser * Functional earth * Fundamental * Fuzz * FX
The definitions for these terms are given on the assumption of their use in the context of PA systems; many of the terms have more general meanings when used in a wider context. Where more than one definition is given for a term, the definitions are numbered (1), (2) etc.
Some of the definitions themselves use terms (such as "signal") in a specific way − most of these are links (just the first time they are used, in each definition), so just click on them to see the meanings that are intended.
F-hole
The sound hole of a
member of the violin family of instruments. Each hole
(of which there are two) is in the shape of a lower-case
letter 'f', hence the name. A similar-shaped pair of
sound holes is found on some types of
semi-acoustic guitar.
Fade down
To reduce the level of a
signal, either by using a
fader or by a remote or
automatic means that controls a
VCA.
Often, but not always, implies a gradual action
rather than a rapid one.
Fade out
To reduce the level of a
signal until it can
no longer be heard, either by using a
fader or by a remote or
automatic means that controls a
VCA.
Often, but not always, implies a gradual action
rather than a rapid one.
Fade up
To increase the level of a
signal, either by using a
fader or by a remote or
automatic means that controls a
VCA.
Often, but not always, implies a gradual action
rather than a rapid one.
Fader
A control, of a mixer
or amplifier, that
allows the level of a
channel, a
group or an overall
mix, to be adjusted.
It is usually of the
slider type.
See also
Potentiometer,
Master,
Fade up,
Fade down,
Fade out,
Travel,
Taper,
Noisy,
Dirty (2),
Unity gain,
0 dB (2) and
Motorised fader.
Farad
The unit of
capacitance, usually
abbreviated to 'F', named after the inventor Michael
Faraday. As a farad is an extremely large amount of
capacitance, more usual units are the microfarad (µF,
one millionth or 10−6 of a farad), the
nanofarad (nF, one thousand-millionth or
10−9 of a farad) and the picofarad
(pF, one million-millionth or 10−12
of a farad). Compare Henry.
Fault protection
In electrical
safety, the collective name given to measures intended
to provide protection against electric shock caused by
indirect contact,
that is, electric shock occurring as a result of
leakage (or short-circuit)
of current to
conductive parts that
are not intended to be live (at a dangerous
voltage) in normal use.
This protection is provided by the connection of accessible conductive parts to a safety earth ('earthing' or 'bonding'), or by the provision of additional insulation between such conductors and parts that are intended to be live ('double insulation'). Further protection may be provided by a suitable RCD, but this should not be the sole means of fault protection. Compare Basic protection.
FCC
An abbreviation for 'Federal Communications
Commission', the U.S. government agency responsible
for the control of electronic communications and
communications equipment in the U.S.A., including the
placing of requirements upon other types of equipment
to avoid problematical levels
of radio-frequency interference
(RFI). See also EMC.
Feed
A supply of a signal
to or from a particular point, or the
cable (or radio
channel, etc.)
carrying that signal.
May also be used to refer to a supply of
mains electrical power.
See also Line and
Drive (1).
Feedback
The situation where the
output
of a PA system, or some part of it,
is deliberately or accidentally supplied back into its
input.
Usually refers to either:
- The undesirable continuous sound (often at a single frequency) which results from too high an overall gain around a complete loop through the system, from microphone, through mixer and amplifier, to speaker and back (through the air) to the microphone again. For more details see Potential acoustic gain. For practical guidance on avoiding this kind of feedback, see the FAQ.
- The intentional continuous sound generated by an electric guitar when held close to its backline speaker or combo, when the controls of the guitar and of the backline amplifier or combo are appropriately adjusted. This is caused by the vibration of the guitar body and strings being reinforced by the sound coming from the speaker.
The above cases are examples of acoustic feedback, where sound waves through the air are involved at some point in the feedback loop. The American term for this kind of feedback is 'howl-round' (occasionally 'howl-back'), written with or without the hyphen, or as two separate words. Other kinds of feedback are:
- Electrical − where the output signal of an amplifier is fed back into the input purely through electrical connections. Although some types of effect unit use this as the basis of their internal operation, the feedback must be very carefully controlled. Do not attempt such a connection yourself, or equipment may be severely damaged.
- Magnetic − where a magnetic field is involved at some point in the feedback loop. An example of this would be the undesirable pick-up of the field from an induction loop by a guitar pickup.
Therefore, feedback may be suppressed by any means which reduces the overall loop gain. In the case of acoustic feedback, such means could include one or more of the following:
- Reducing the amount of amplification that the PA system gives to signals picked-up by microphones. In order to avoid a corresponding reduction in the sound level experienced by the audience, it may be possible to reduce the distance between the microphone(s) and their respective sound sources. (Alternatively, or additionally, it may sometimes be possible to reduce the distance between the speaker(s) and the audience.)
- Reducing the number of microphones that are open at any one time (see NOM). In any case, it is good practice to ensure that any microphones not in use are muted.
- Changing the position or orientation of the microphone(s) or speakers, in order to reduce the sound level from the speaker(s) that is picked up by the microphones. In this regard the polar response pattern of each microphone and the directivity of the speakers will be need to be taken into account.
- Introducing attenuation into the signal chain at the feedback frequencies (by use of equalisation facilities, typically a graphic equaliser) − see Feedback destroyer and Ringing out.
- Modification of the room acoustics, for example by the introduction of additional absorption at the feedback frequencies.
Feedback destroyer
An item of equipment whose purpose is to assist in
the elimination of acoustic
feedback by the introduction of
attenuation
into the signal chain at
the feedback frequencies.
It is usually connected between the
mixer and the
power amplifiers.
These devices vary in sophistication and in effectiveness.
See also Ringing out.
Female
Describes a
connector that makes
all or most of its connections by means of receptacles.
Such a connector is loosely known as a
'socket'
− especially when it is of the type that is fixed to
equipment. See also Gender
and Mate.
Compare Male.
Ferrofluid or
Ferro-fluid
A liquid used to assist in the cooling of
high-power driver
voice coils,
by conducting heat from the coil to the surrounding
permanent magnet assembly.
It consists of specially-coated magnetic
nano-particles suspended in a carrier liquid,
and is held in place by the permanent magnetic field.
Usage is generally limited to
tweeters /
horns and
mid-range drivers,
because in low-frequency drivers
(woofers) the coil excursion
is too large for the fluid to be held reliably in place.
Its viscosity contributes to the forces that restrain
motion of the voice coil and as such is part of the
driver's dynamic (as well as thermal) design, therefore
it cannot be added to a 'dry' driver retrospectively.
See also
Power compression.
FET
An abbreviation for 'field-effect transistor',
a semiconductor
amplification
device characterised by a very high
input impedance
and a low
output impedance.
Typically used in the
input stage of
pre-amplifiers
requiring a very high input impedance, such as the
internal pre-amplifiers of
condenser
microphones.
See also MOSFET.
FFT
An abbreviation for 'fast Fourier transform', a
computationally efficient technique for conversion of a
signal from the
time domain to the
frequency domain,
suitable for real-time applications such as
frequency-domain
digital
filters.
Based on the principles of
Fourier
analysis.
Fibre-optic
See Optical
interface.
Fidelity
The degree to which a reproduced
sound (or visual image) remains
faithful to the original
acoustic (or visual) source.
That is, the degree to which the original source
programme is accurately
reproduced by equipment for recording, playback,
amplification or
signal processing,
or by a speaker.
See also Hi-Fi.
Field (1)
An abbreviation for
'jack field'.
Field (2)
In a video display system, the set of
raster lines
that are scanned consecutively in one sweep from the
top of the picture to its bottom. In a
progressively
scanned system a single field encompasses all
the lines of the raster
frame. In an
interlaced
system, however, a field consists of alternate
raster lines and so two interleaved fields (an
odd field and an even field) are required to complete
the frame. Therefore, in the UK 625-line
standard-definition broadcast video system having a
frame rate of 25 Hz,
the field frequency
is 50 Hz. See also the next definition.
Field sync
In an analogue video
signal, the
synchronisation
pulses that indicate the start of each
field of the picture.
In the UK 625-line standard-definition broadcast video
system, the pulses occur at
a frequency of 50 Hz,
an interval of 20 ms.
The field sync pulses are arranged as a group
and are preceded and followed by a group of
'equalisation pulses' (no connection with audio
equalisation).
Both field and line sync
pulses occupy the negative-most
0.3 volts of a
standard 1 volt peak-to-peak video
waveform.
See also Composite
video and
Frame (2).
Fifth
An interval of musical pitch that
corresponds to a frequency
ratio very close to 1.5
(in practice the value is closer to 1.4983).
So, two frequencies are said to be a fifth apart when one
frequency is 1.5 times (or, of course, 2/3 of) the other.
For the musically minded, a fifth is so-named because a fifth interval is reached at the 5th note of a tonic musical scale. Between the lowest and highest of these 5 notes are 4 intervals, made up of 3 tones and 1 semi-tone. Since a tone is a ratio of the sixth root of 2, and a semi-tone is a ratio of the twelfth root of 2, we can see that multiplying out these 4 intervals (i.e. 21/6 x 21/6 x 21/6 x 21/12) gives a resulting ratio very close to a value of 1.5, i.e. a fifth. See also Octave.
Fifth-order
See Order.
Figure-of-8 cable
An un-screened
two-conductor
cable which does not have a
sheath. The two
insulated conductors
are laid side-by-side (without a twist) and the touching
edges of the insulation are bonded together along the
length of the cable, giving the cross-section of the
cable the appearance of a number 8. The bonding can easily
be torn apart at the ends of the cable, to separate the
conductors for stripping and
terminating.
As the insulation of the two conductors is usually the same
colour (generally white or grey), the surface of one
conductor's insulation is usually marked with a stripe or
a raised rib, for identification purposes.
The lack of a sheath means that this type of cable has
inadequate mechanical protection for rough stage use, so it
is generally used only for permanently installed
interconnections. Also called 'zip cable'.
Figure-of-8 microphone
See
Bidirectional
microphone.
Fill
Supplementary sound,
provided specifically to cover areas that are not adequately
covered by the main
front-of-house
or monitor system(s).
Or, the speakers that provide
such supplementary sound, or other associated equipment.
Terms used to identify specific types of fill include
front-fill,
side-fill and
downfill.
Filter (1)
A device which applies a different amount of
attenuation to different
frequencies contained in
a signal, usually in order to
remove (or to very substantially reduce in
level) some unwanted part
of the signal, or to select a specific part of the frequency
range. Filters may be passive
or active.
See also Equaliser,
Crossover,
Low pass,
High pass,
Bandpass,
Bandstop,
Cut-off frequency,
Centre frequency,
Passband,
Stopband,
Order,
Brick wall filter,
Chebyshev,
Butterworth,
Bessel,
Linkwitz-Riley,
FIR and
IIR.
Filter (2)
A device, used within a lantern,
which allows only certain wavelengths of
light to pass and therefore
gives the emitted light a specific colour.
Also called a 'gel' (short for gelatine, a material from
which filters may be made).
Finalise
The process of creating the table of contents (TOC)
on a recordable audio compact disc
(CD-R) or on a re-writable
audio compact disc (CD-RW).
This process is necessary in order
to make the disc playable on an ordinary CD player, though
CD recorders can usually play discs without a TOC.
Compare Unfinalise.
See also PMA.
FIR
An abbreviation for 'finite impulse response'.
Describes a time-domain digital
filter which incorporates
only feed-forward paths. This avoids the stability and
rounding error problems that can sometimes be encountered
with IIR types and enables designs
with a linear phase response
to be implemented, giving constant delay across the
frequency response.
The name arises because the filter's response to an impulse
input is time-limited.
First generation
Describes an original recording − one that is
not a copy. See also
Generation.
First-order
See Order.
Flanger
An effect unit which
provides a sweeping kind of effect, often fairly extreme
and harsh-sounding. Used mostly by guitarists.
Flanges
See 19
inch rack system.
Flat (1)
Describes a
frequency response
(e.g. of an amplifier)
that gives an essentially constant output
level regardless of
frequency, given that input
signal remains at the same level.
For example, if some
equalisation controls were set
so as to have no effect on the
signal,
they would be described as being 'set flat'.
(This is most evident in the case of a
graphic equaliser,
where the position of the slider controls would physically
form a flat line.)
Flat (2)
A movable vertical surface on which stage scenery is
painted. See also
Scene (1),
Set (2) and
Cyclorama.
Flat (3)
Describes a musical note whose
pitch is lower (usually,
just a little lower) than it should be.
See also Bum note.
Compare Sharp.
Fletcher-Munson
curves
See A-weighting.
Flight case
A strong box, usually having handles, metal edging strips
and a padded interior, for protecting equipment in transit.
It often also has castors (wheels).
Compare SKB.
Float
In digital audio,
an abbreviation for 'floating point format'.
A standardised word format in
which the available bits are
split into two groups − a group (called the mantissa)
which specifies a value within a normalised range (typically
between 0 and 1) and a group (called the exponent) which
specifies the number of 0's to be appended to the mantissa
to give the required overall value. This format is normally
only used in interfaces
between the software modules of digital audio packages
(see DAW); it is not used over
physical interconnections.
The float format allows very much larger values to be conveyed by a given number of bits, so hugely increasing the available dynamic range and thus avoiding overflow errors during digital signal processing. However, this advantage is at the expense of a less accurate representation of the sample values than would be obtained had all the bits been used in a linear manner, so the float format is not usually used with word lengths of less than 24 bits.
Float switch
See Earth lift.
Floating
Describes an interconnection, or an
input or
output, whose
conductors have no
low-impedance path to
signal earth.
For example, the output connection of a
dynamic
microphone, a MIDI
input connection or an earth-free
transformer-balanced
input or output. See also
Balanced,
Earth lift and
Quasi-floating.
Floor
The lowest level
reached by a signal
(compare Peak).
Or, short for
'noise floor'.
Floor monitor
A monitor
speaker that is designed
to rest on the floor. Usually wedge-shaped, so often
referred to as a 'wedge' (or sometimes as a 'slant').
Floor tom
Part of a drum kit; a large
low-pitched
drum with short legs that stand on the ground.
See also Kick.
Compare Rack tom.
Fluff
To make a mistake during a performance, especially
in a vocal or spoken line or in an instrumental solo.
See also Bum note.
Fly
The act of suspending something (usually
speakers)
overhead. Requires careful attention to
safety.
See also SWL and the next
definition.
Flyware
The hardware used for the
flying of equipment, especially
speakers.
See also SWL and
Rigging.
FM
An abbreviation for 'frequency modulation'.
See Modulation.
FOH
An abbreviation for
'Front-of-house'.
FOH mixer
See
House mixer.
FOH engineer
A sound engineer
who is responsible for the
front-of-house
sound. Compare
Monitor engineer.
Foldback
The sound mix that is
supplied to monitor
speakers.
Note: Non-technical personnel are liable to confuse
the term 'foldback' with 'feedback'.
Folded horn
A speaker in which
the driver faces back into
the enclosure,
which contains a horn
made up of surfaces that are angled or curved so as to direct
the sound to the aperture at the front of the enclosure.
An arrangement most usually found in
bass bins and lower-mid-range
speakers, where folding the horn is a useful way of
accommodating its large size.
Follow-spot
A high-power spotlight that is readily moveable during
a performance, to enable the movements of an on-stage
performer to be tracked. Usually has its own operator, who
physically points the spotlight as instructed via
a communications link.
Foot drum
An alternative name for a
kick drum.
Forced cooling
The use of one or more fans to assist in the
cooling of equipment by increasing the air-flow through it.
Usually mounted internal to the equipment, and used in
conjunction with a heatsink.
The flow of air must not be obstructed, or
the equipment may overheat and be seriously damaged.
Formant
A region in a natural
sound's
frequency spectrum
containing particularly high energy
levels, caused by
acoustic
resonance of the
space(s) in which the sound is created or through
which it passes. The formants of the spoken word
(or song) vary during vocalisation, and are
particularly important in the
identification of different vowel sounds. In the
case of acoustic instruments, the formants are an
important contributor to the
timbre of the
instrument. Significantly, the formant frequencies
are essentially independent of the
pitch being sounded
by a particular person's voice or by a particular
instrument.
Format
Literally, "layout" − the agreed scheme or rules
according to which information is arranged, coded or
represented for conveying between points as a
signal, or for storage,
or according to which information is presented.
Fourier
analysis
The determination of the individual
frequency
components of a complex
waveform. Named after the
mathematician Fourier, who established that any
continuous repetitive waveform may be
considered to consist of a number (often large) of
individual sine waves,
in specific proportions, each of which is an exact
multiple (from 1 upwards) of the repetition rate or
'fundamental frequency' of the waveform. The
multiples from 2 upwards are called
harmonics.
This process is used in
digital
signal processing
to enable the manipulation of waveforms in the
frequency domain − see
FFT.
Likewise, it is possible to synthesise (i.e. construct) any waveform by the addition of harmonics, in the appropriate proportions, to the fundamental. This approach to sound generation is used in some electronic keyboard instruments. See also Principle of superposition.
Fourth-order
See Order.
Frame (1)
In a digital
bit-stream or
recording, a
sequential collection of bits
having a means to identify its start and having a
defined internal format. Frames follow on one after
the other ad-infinitum.
In digital audio tape-recording (DAT), frames of data are recorded at the rate of 100 frames every 3 seconds. Each of these frames consists of 1440 16-bit samples of the Left channel and 1440 16-bit samples of the Right channel, plus subcode data. (So, the maximum supported sample-rate is 48 kHz.) The frames are uniquely identified by absolute time code (ATC) stored in the subcode data.
In AES3 and S/PDIF bit-streams, a frame of data consists of two sub-frames, one for the Left channel and one for the Right channel. Each sub-frame contains 32 bits of data, of which between 16 and 24 (usually 16) constitute a single audio sample; the remainder contain subcode data and other control and synchronising information. The frame rate is the same as the sampling rate in use (32, 44.1 or 48 kHz). 192 of these frames make up a 'block', which constitutes a complete structure of the subcode information. (Note, however, that the subcode structure varies between AES3 and S/PDIF.)
Frame (2)
In a video display system, one complete scan
of the picture, encompassing all the lines of the
raster. In an
interlaced
system, a frame consists of two interleaved
fields of lines.
Therefore, in the UK 625-line standard-definition
broadcast video system having a
field frequency of
50 Hz,
the frame rate is 25 Hz. See also
Field sync.
Free field
Describes a location at which
direct sound
energy from a particular sound source predominates over the
indirect sound energy
from that source. Within the free field, the
inverse square law
applies.
Compare Diffuse field
and Near field.
See also Radius
of reverberation and
Critical distance.
Frequency
A measure of how rapidly something is repeating.
In relation to an audible
sound or
signal, frequency is a measure
of how rapidly each
cycle of it is repeated
− this determines its musical pitch. The unit of
measurement is the hertz (usually abbreviated to 'Hz'),
which is a rate of repetition of one cycle per second.
The human ear can detect sounds
in the approximate frequency range of 20 Hz to
20 kHz, though this
varies from person to person and depends on the
level of the sound.
Middle C on a piano ('C4') has a
fundamental frequency
of approximately 262 Hz, and the 'A' above middle
C ('A4') has a standardised frequency (at 'concert pitch')
of exactly 440 Hz.
See also Octave,
Wavelength,
Bass (1),
Treble,
Mid-range,
Equaliser,
Graphic equaliser,
Crossover,
Filter and
Fourier analysis.
Compare Rate.
Frequency
agile
Describes a radio system (such as is used within
radio microphone
and in-ear monitoring
equipment) that is user-configurable to operate on any
of a number of different
radio frequencies,
or 'channels'.
Frequency
modulation
See Modulation.
Frequency response
An indication of the way in which the
output
level of an
item of equipment is dependent upon the
frequency of the
input
signal, given that the
input level remains constant as its frequency is varied
through the entire range of interest.
Most often, the term is used as an indication of the
range of frequencies which are adequately handled by the
equipment, and in this case it is usually quoted as the
upper and lower frequencies at which the output level of
the equipment has reduced by 3 dB,
relative to its output level at some mid-band reference frequency
(often 1 kHz,
for audio
equipment). These are referred to as
the '−3 dB' frequencies, and are the frequencies
at which the output would give half the
power
(not half the voltage)
of that obtained at the reference frequency, given
the same level of input.
(See the Decibels page
for more information on decibels.)
Because such a substantial drop in output would usually be unacceptable even at the limits of the audio range, and because the drops occurring in several items of equipment will accumulate when they are connected together in the signal chain, it is usual to find frequency response figures quoted that are outside the actual frequency range of interest. For example, an amplifier with a quoted −3 dB frequency response of 10 Hz to 50 kHz is likely to have a response between, say, 20 Hz and 20 kHz that dips only marginally below the output obtained at 1 kHz. See also Cut-off frequency, Flat and Slew rate.
Frequency
shifter
A device used to increase the amount of
amplification
possible before the onset of
acoustic feedback.
It achieves this by causing the
sound from the speakers
to be offset in
frequency relative
to the sound source −
typically by around 5 Hz.
Good for speech (e.g. presentations and theatre),
but of very limited use for music because the
all-important
harmonic relationship
between the frequencies is disturbed. For example, after
frequency shifting a note at 400 Hz upwards by 5 Hz,
it is no longer an octave
above a note at 200 Hz that has been shifted by the same
amount, because although 400 is exactly 2 x 200,
405 is only approximately 2 x 205.
Frequency
spectrum
See Spectrum.
Fresnel
A type of lantern
that uses a specific kind of lens, having a 'stepped'
surface. This lantern gives a diffuse beam of light
with soft edges. Named after its inventor, and pronounced
'fren-ell'. See also
Wash light.
Fret buzz
An undesirable sound caused by a vibrating guitar
string contacting one or more frets that it
should be clear of, or improperly contacting a fret
that it should be in hard contact with. Sometimes this
sound can be confused with unwanted
distortion of the
guitar signal.
Front end
The input stage
of a radio receiver, handling the
radio-frequency
signal direct from the
reception antenna or
antenna
distribution unit.
Front-fill
Supplementary, lower-power
front-of-house
speakers
required to improve the coverage
at the very front of the audience. May be
flown or placed on the front
edge of the stage apron.
See also Downfill
and Side-fill.
Front-loaded
Describes a speaker
enclosure that has its
driver(s) mounted into it
from the front. This is the most common method of
mounting drivers in modern enclosures.
Front-of-house
The area forward of the stage − i.e.
the area occupied by the audience.
In PA work, the term is most
often used in reference to the
speakers
directed at that area − or sometimes to refer to
the specific location of the front-of-house mixing position.
However, the term may also be used in non-PA contexts, such
as to refer to the lighting serving the audience area.
Commonly abbreviated to FOH.
See also the next definition and
Auditorium,
House (and following terms
such as House mixer),
Monitor mixer and
Backline.
Frontline
The speakers directed
at the audience, more frequently described as
'front-of-house'
(FOH).
Compare Backline.
FS
An abbreviation for
'full scale'; see, for
example, dB FS on the
Decibels page. See also
Over.
Full-duplex
See Duplex.
Full
normalling
See Normalling.
Full range
Describes something which adequately covers the
majority of the audible
frequency
spectrum of
20 Hz to
20 kHz, and is
therefore suitable for use without the need to provide
additional equipment covering specific parts of
the spectrum. Usually used as a description of
speakers.
In practice, equipment such as speakers rarely covers the whole of this frequency range − see Frequency response. However, a speaker with an effective frequency response of, say, 50 Hz to 18 kHz would still be described as 'full range' because, in appropriate circumstances, it could be used without additional speakers to cover the missing parts of the spectrum at the extreme top and bottom ends.
As a single type of driver is unable to satisfactorily reproduce the full audio frequency spectrum, a full-range speaker usually contains at least two (sometimes three) different types of driver. The bass drivers are called woofers and the treble drivers are called horns or tweeters. (Mid-range drivers have no particular name.) It is essential that each type of driver is supplied only with the relevant band of frequencies. This is achieved either by use of a passive crossover to split the output of a single amplifier, or by use of separate amplifiers for each frequency band, in which case the amplifiers are fed from an active crossover − see Bi-amping.
Full scale
The highest possible
value of some quantity, or the highest value that may be
registered, often abbreviated to 'FS'. For example, see
dB FS on the
Decibels page. See also
Over.
Full space
A measurement environment in which the whole of the space
around the item under test is considered.
Most often used in
anechoic measurements
of speakers, where it
simulates the speaker being used away from any reflective wall
and so gives lower sensitivity
figures at bass
frequencies.
Also referred to as 4-pi space.
Compare Half space.
Fully
normalled
See Normalling.
Fully
parametric equaliser
See Parametric
equaliser.
Functional
earth
See Technical
earth.
Fundamental
See Harmonic.
Fuzz
A now little-used term for intentional
distortion introduced
as an effect, usually
for an electric guitar. The unit to produced this effect
is called a 'fuzz box' (now more usually called a
'distortion pedal').
FX
In PA work, an abbreviation
for 'effects'.
However, other technical staff may use this abbreviation
to refer to
special effects.
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There are no more definitions on this page. (The space below is to ease linking to the last few terms above.)
0-9 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
This page last updated 11-Jun-2009.