Audio/Visual
An A/V system consists of components for the
reproduction of audio (sound) as processing
of audio (from CD, Tape, VCR, Laserdisc, DVD, etc.) and video signals
(from VCR, Laserdisc, DVD, etc). Normally, there will also be outputs
for speakers and TV enabling the A/V amplifier or receiver to act as the
control center of a complete Home Entertainment installation.
Adjustable
Bass Reflex
An adjustable bass reflex port that makes it possible to
tune a subwoofer according to its location in the room and the taste of
the user.
Alternating Current
Type of electricity that is available from mains outlets.
Batteries supply DC (Direct Current).
AC3 RF
Most Laserdisc players deliver Dolby Digital (AC3) RF (Radio Frequency)
modulated signals that have to be converted into digital bit stream
signals before processing in many A/V amplifiers and receivers.
Accelerometer
Electronic
instrument used to measure acceleration. Mounted on the diaphragm of a
loudspeaker, an accelerometer is able to register the acceleration
(equivalent of near-field sound pressure) and deliver a correction
signal to the amplifier via a feedback circuit, to ensure that the
waveform of the output is equal to that of the input.
Acoustic
Suspension
Also
referred to as a Closed box. Sealed loudspeaker enclosure where the
trapped air acts as a spring that controls the excursions of the woofer
diaphragm. Acoustic suspension may improve the transient response and/or
extend the low frequency range of a loudspeaker system, at the cost of
efficiency.
Active
Generic term
indicating that a passive component, such as a loudspeaker, contains
active circuitry - amplification, signal processing, etc.
Active
Speaker
Loudspeaker
system with built-in power amplifier and, in most cases, signal
processing and/or equalization to optimize the interface between the
speaker unit(s) and the electronics.
An active speaker may be driven
from almost any low-level line output available on A/V and multimedia
equipment plus personal stereo components, such as portable cassette
tape, CD and Minidisk players.
Analogue
Dialogue Normalization
This feature maintains a uniform level of Dolby
Digital software when you switch between film titles, without decreasing
the signal to noise ratio. You will always experience the full dynamic
range together with the level that you consider most appropriate.
Ambience
The
experience of "space" or "air" during the
reproduction of audio software.
Amplifier
An
electronic device that will increase the level and/or power of an input
signal. In general, an audio amplifier consists of two main sections - a
control amplifier for level control and tonal adjustments plus a power
amplifier that is able to deliver the necessary currents to drive
loudspeakers.
Analogue
Something
similar or parallel to something else. The waveforms correspond to the
original audio and/or video signals. Analogue programmed sources include
LP records, cassette tape and VCR, plus conventional radio and TV
programs. Generally speaking, "analogue" stands for "not
digital"
Anechoic Chamber
A
room where the reflected sound energy is almost negligible. Used for the
measurement of speaker and microphone characteristics.
Aperiodic
Chamber
Normally
when using large woofers in a small cabinet, the result will be an
overshoot just before the woofers start rolling off, resulting in
excessive bass reproduction at low frequencies.
By venting the cabinet
with a number of holes in the rear panel, representing approximately 20%
of the woofer diaphragm area, the loudspeaker will cancel itself
acoustically. The result is a dampening of the overshoot and
consequently an authoritative and precise dialogue reproduction. Even
though we acoustically short circuit the low frequencies, there will be
plenty of bass reproduction. Only the lowest frequencies are lost, and
they are of no importance, anyway, as the low bass information can be
routed to an LFE (Low Frequency Effect) channel on Dolby Digital
equipment or to a separate subwoofer out terminal on Dolby Pro Logic
decoders.
Anti Resonance Compound
The ARC technology allows for stylish, yet resonance dead, front baffle
designs. The technique behind this is a combination of a die-cast
plastic shell and a piece of shaped MDF or chipboard. The two parts are
glued together using a special resonance dead binding agent, and the
result is a very rigid sandwich construction.
Baffle: The front
part of a loudspeaker enclosure where the drivers are mounted.
Banana Plug
A plug
with banana shaped springs that give a low resistance transfer of e.g..
loudspeaker signals. In Europe, the banana plug is now outlawed by the
EU Low Voltage Directive as being potentially hazardous.
Band
Pass Filter
An
electronic filter that attenuates frequencies above and below the
specified band pass frequency. A typical application of a band pass filter
is the part of a crossover network that drives a midrange unit in a
three way system.
Bandwidth
The range
between the lowest and the highest frequencies that an electronic system
is able to reproduce.
Bass: Sounds in
the low audio frequency range, typically frequencies below 500 Hz.
Bass Reflex
A
vented loudspeaker enclosure in which the rear waves from the woofer(s)
emerge through an opening or bass reflex port that is tuned to the
woofer characteristics. A correctly designed bass reflex enclosure may
feature higher efficiency and/or deeper bass than e.g.. an acoustic
suspension cabinet.
Biamping
Connection
of a loudspeaker system to two amplifiers. One amplifier is dedicated to
the upper tone range (typically treble and midrange) while the other
powers the lower tone range (typically bass). Requires loudspeakers
prepared for biwiring.
Biwiring
Connection
of a loudspeaker system to one amplifier via two, often different,
speaker cables. A popular way to fine tune the sound by exploiting the
virtues of various cable designs. Requires loudspeakers with separate
low and high range terminals and crossover sections.
Breakup
When a
speaker's diaphragm movements are not pistonic, at higher frequencies,
the cone is said to "break up" in patterns that move out of
phase with each other. The larger the diaphragm, the lower is the
breakup frequency above which the frequency response becomes highly
unlinear and "rough" to the ears.
Bullet
A bullet
shaped metal or plastic "nose" typically mounted in the center
of a midrange or woofer. When using a bullet (often referred to as a
phase plug), it is not necessary to mount a dust cap over the voice
coil.
Using a bullet prevents break-ups around the mounting point of the dust
cap. If the bullet is made of metal, it will furthermore remove heat
from the magnet system enabling the unit to handle more power.
Capacitor
Frequency
dependent electronic component featuring an impedance that is inversely
proportional with frequency - the higher the frequency, the lower the
impedance. In crossover networks, capacitors are used, for instance, to
ensure that low frequencies do not reach tweeters.
Compact Disc
The digital audio disc format that was introduced in
1982/83. For audio applications, the main specifications of the 12 cm
diameter disc are: 74 minutes of playing time and a 44.1 kHz sampling
rate with 16bit quantization, that translates into a frequency range up
to 20 kHz and a dynamic range of up to 96 dB.
Compact Disc - Read Only Memory
Physically identical to the CD but
dedicated as a carrier for all kinds of computer data. With a capacity
of 650 Mb, the CDROM is ideally suited for PC applications and
multimedia software.
Center
Modes
Modes
available for optimization of the center channel reproduction in Dolby
Pro Logic amplifiers and receivers. The user is able to select between
"Normal" (for relatively small center speakers) "Wide(band)"
(for relatively large center speakers) and "Phantom" (for a
systems without a center speaker) modes.
The "Normal" mode
diverts the low frequency center channel information to the main (front)
speakers, while the "Phantom" mode divides all this
information equally between the main speakers.
Center
Speaker
A
vital part of any Home Entertainment system, dedicated to the
reproduction of the center or dialogue channel in a Home Entertainment
system. The center channel should act as an acoustical extension of the
TV or projection screen. This means that the center speaker should be
located on top of, below or behind the screen, as close as possible to
the picture.
Channel
A complete
sound path from microphone to loudspeaker. A stereo system has two
independent channels, and the latest surround formats are discrete 5.1
channel digital systems.
Chipboard
Fiber board made of compressed wood chips. Chipboard features good
price/value ratio, good acoustic properties and high mechanical
stability. These qualities make chipboard the preferred material for
budget speaker cabinets.
Class D
Highly
efficient amplifier design that can turn up to about 90 per cent of the
dissipated power into driving power for loudspeakers. At the present
state of development, Class D amplifiers are mostly used for low
frequency signals, e.g.. for subwoofers.
Clipping
Distortion
arising when an amplifier is overdriven - forced to deliver higher
output signals that its design and/or power supply permit. Viewed on an
oscilloscope screen, the top and bottom of a clipped signal look like
they have been cut off. Even if clipping occurs in the low frequency
range, the harmonic distortion products may be strong enough to
seriously damage a delicate tweeter.
Coaxial
A coaxial
cable consists of a conductor surrounded by an insulating material and
shielded from external electromagnetic influences by a metal screen.
Coaxial cables, typically fitted with cinch (RCA, phono) plugs are
extensively used for the transfer of line level electrical signals
between Home Entertainment components.
Coloration
Subjective
term describing the listening experience when the sound is not true to
the original. Examples of coloration include warmness and harshness.
Compatibility
The
degree to which hardware or software may be used in whole or partly with
other systems. Most Home Entertainment components are
"backwards" compatible. A DVD player, for instance, can
reproduce CD software, and a Dolby Digital amplifier will also be able
to decode Dolby Pro Logic material.
Component: An
electronic or mechanical part, or an independent unit such as a player,
amplifier or speaker in a Home Entertainment system.
Cone: Another
word for the (conical) diaphragm of a speaker unit.
Control amplifier
A
separate component or the part of an integrated amplifier that performs
level control and tonal adjustments.
Crossover
Frequency
The
frequency at which equal power is delivered to each of the adjacent
units in a multiway speaker system. In a typical two-way system, the
crossover frequency between the woofer and the tweeter will be set
around 2.500 Hz.
Crossover Network
An
electronic filter in a multiway speaker system that separates the signal
from the amplifier into two or more frequency bands for the woofer,
tweeter and possibly midrange unit.
Current
feedback
A
feedback technology that reduces acoustic distortion in active
loudspeakers by measuring the current flow through the speaker units and
comparing the current waveform with the input signal. A distortion
reduction around 10 dB can be realized with current feedback.
Cut-off frequency
The
upper or lower frequency limit of a piece of electronic equipment. The
cutoff frequency of e.g.. a subwoofer will typically lie in the 100 - 200
Hz range, indicating that the subwoofer has been designed to reproduce
tones from the lower limit of audibility up to that frequency.
dB
Decibel. A method of describing one level of
e.g.. sound pressure level
(volume) to another. In this connection, 6 dB corresponds to a doubling or
a halving of the sound pressure.
dB/octave
Indication
of the attenuation (steepness or slope) of an electronic filter. Typical
filters may have a slope of 6 dB/octave (1st order filter, 12 dB/octave
(2nd order filter), and so on.
DC
Direct
Current, the type of electricity that is available from batteries and
power supplies for Home Entertainment equipment.
Decoder
An
electronic device that converts one type of signal into another. A Dolby
Digital decoder converts a digital bit stream into 5.1 channels of analogue
information.
Diaphragm
The part
of a speaker unit that converts the oscillations of the voice coil into
air pressure variations = audible sound. Traditionally, the speaker
diaphragm is cone shaped. High frequency units (tweeter) are often dome
shaped.
Diffraction
The
reflection and diversion of sound waves around sharp edges such as those
on speaker cabinets or fabric frames. The high frequency range is
particularly sensitive to diffraction which is experienced as (slight)
distortion/coloration of the audio image.
Digital
General
term indicating that some kind of information is represented by numerical
values - zeros and ones.
Digital
inputs/outputs
Sockets
for digital audio signals in optical or electronic forms. Optical cables
mostly use so called To slink plugs, while electronic cables have coaxial
phono or BNC connectors.
Digital to analogue
conversion: The conversion of digital data into analogue audio and/or
video signals.
Digital
TV
Transmission
and reception of digitized video and audio information. Digital TV holds
the potential for higher quality and better economy, because many more
channels can be accommodated within the existing terrestrial and cable
networks.
Dipolar
In Home
Entertainment, a dual surround speaker design consisting of two systems
operating out of phase. Combined with an acoustic cancellation, this
creates a diffuse sound field (ambient and spacious). Dipolar surround
speakers are required by the Home THX specification.
Directivity:
An
indication of the way that sound waves from a speaker are radiated into
the room. The Home THX requirements state that the front speakers should
have a wide horizontal directivity (spread), and a tightly controlled
vertical spread.
Discrete
In this
context synonymous with separate. An amplifier may be built from discrete
electronic components (contrary to integrated circuits), and Dolby Digital
produces 5.1 discrete (perfectly separated) sound channels. Not to be
confused with "discreet" (unobtrusive).
Dispersion
Distribution
of sound from a speaker into the listening room over a given angle.
Dolby 3
Stereo
Seldom
used Dolby Pro Logic mode that works without surround speakers.
Dolby
Digital
Dolby
Digital is the new digital surround format from the inventors of Dolby
Stereo. Dolby Digital produces not only five discrete (perfectly
separated) sound channels and a dedicated LFE (Low Frequency Effects)
subwoofer channel, but also offers the benefits of an all digital system
in terms of crystal clear sound without distortion and noise. Compared to
Dolby Pro Logic, the sonic improvement almost corresponds to stepping up
from cassette tape to CD.
Dolby Pro
Logic
The
most widely used Home Entertainment process. Produces a surrounding sound
field with Dolby Surround or Dolby Stereo encoded software. This includes
practically all major films from the late seventies and onwards available
on VHS videotape, Laserdisc, DVD or from stereo TV.
Dolby
Stereo: Four-channel
surround sound format for film soundtracks.
Dolby
Surround: Four-channel
surround sound format for TV and video soundtracks.
Dome
Tweeter
High
frequency loudspeaker unit with a dome shaped diaphragm. Features better
linearity and wider dispersion than a conventional unit with a cone shaped
diaphragm.
DPL: Dolby
Pro Logic.
Driver: In this
context, synonymous with speaker unit.
DSP:
Digital Signal Processing
When dedicated microprocessors manipulate audio
signals in the digital domain, they are able to simulate acoustic sound
fields like those found in concert halls, churches, jazz clubs, etc. DSP
technology is also employed for the decoding of the various surround sound
formats.
DTS
Digital Theater System. DTS works with the same channel configuration as
Dolby Digital. The main difference being a higher bit rate in DTS, which
gives this system potential for an even higher sound quality.
DVD
Digital Versatile Disc. Optical disc with the size and the looks of a CD,
but featuring a much higher data storage capacity. While a CD is able to
store 650 megabytes of information, one DVD information layer has a
capacity of 4.7 gigabytes. Since the DVD specification offers the options
of dual layer and/or double sided discs as well, the maximum capacity
amounts to 17 gigabytes.
DVD
Audio
Proposed
standard for an audio only DVD disc, featuring a high sampling rate of 96
kHz and 24bit quantization - equivalent to the best studio recording
equipment available.
DVD
Video
The DVD
Video format makes the dreams of film enthusiasts come true. For the first
time in history, it is possible to enjoy broadcast quality motion pictures
with more than twice the resolution and detail of VHS video tape, plus six
channels of ultra realistic digital surround sound. A single layer single sided DVD Video disc has a playing time of up to 133 minutes, more
than enough for a typical feature film. Other advantages of the DVD Video
format include soundtracks with dialogue in up to eight languages and
subtitles in up to 32 languages.
DVHS
The latest
development of the VHS video format, featuring digital picture and sound
quality plus extended playing time.
Dynamic
Loudspeaker
A
conventional loudspeaker consisting of a permanent magnet, a voice coil
and a diaphragm.
Dynamic
range
The
difference between the loudest and the softest signal that can be
processed by Home Entertainment equipment. A typical dynamic range for a
digital audio component is 96 dB, corresponding to 16bit quantization. Dynamic range
compression: A standard feature in most Dolby Digital processors that
makes it possible to raise low-level signals in volume and limit the
maximum level of loud signals. When the dynamic range of audio signals is
compressed, intelligibility, e.g.. of speech, is improved at relatively low
volume levels.
Electronic
Crossover Network
An active electronic filter in a multiway speaker system that
separates the signal from the control amplifier into two or more frequency
bands for the woofer, tweeter and possibly midrange unit. This type of
crossover network requires separate power amplifiers for each frequency
band. An electronic crossover network eliminates power loss and may easily
be tailored to the characteristics of the individual speaker units.
Equalize: Frequency
manipulation or compensation to obtain a desired frequency response.
Equalizer: Typically
a multiband tone control circuit.
Excursion
The
(maximum) distance that a speaker (typically a woofer) unit may travel
without suffering mechanical damage. So called long throw woofers may
feature peak excursions exceeding 25 mm (1").
Feedback
Error
correction technique of feeding a fraction of the output from a circuit
back to its input. By comparing the two signals, any deviations may be
corrected and cancelled.
Ferrofluid
Magnetic
oil which is used in the voice coil gap of typically a tweeter. Increases
the power handling capacity, because the oil transfers heat to the magnet,
and damps unwanted resonance.
Frequency
The rate
of repetition of both musical pitch and electrical signals. Low
frequencies correspond to bass notes, high frequencies to treble tones.
Frequency
Range
The
range from the lowest to the highest frequency a system is capable of
reproducing. The audible frequency range is generally defined as 20 -
20,000 Hz.
Frequency
Response
Like
frequency range, but with specified tolerances. The frequency response of
a high quality loudspeaker system may be given as 30 - 20,000 Hz, ±3 dB.
Front
Speaker: Main
speaker in a Home Entertainment system.
Fullrange
Speaker Unit
A
single loudspeaker unit which can reproduce the greater part of the
audible range.
Gain: Synonymous
with amplification factor in electronic equipment.
Glass Fiber
Thin fibers of glass that can be woven and used for
e.g.. speaker diaphragms.
Hardware
In this
context, the physical parts of a Home Entertainment system. A DVD disc, Laserdisc or video tape are hardware, but the recorded information is
labeled software.
Harmonic
Distortion
Unwanted
signal components related to fundamental tones. The second, third, fourth
and so on harmonics of 1 kHz are 2 kHz, 3 kHz 4 kHz, etc. Harmonic
distortion is typically expressed in per cent, and should be as low as
possible.
HDTV
High
Definition TeleVision. Possibly the TV system of the future with twice as
many horizontal picture lines and twice the resolution (sharpness) of
conventional TV pictures.
High
Range Matching
Circuit
for the matching of the level of a tweeter to that of other speaker units
in a system. (Jamo feature)
Home THX
Home THX
is not yet another Home Entertainment sound format. Home THX is a quality
standard for Home Entertainment hardware and software.
Whenever a Home Entertainment product bears the "Home THX" logo,
it has been subjected to a stringent series of laboratory and listening
tests conducted by experts at Lucasfilm Ltd. The original THX standard was developed to ensure that cinema audiences
would experience the sound and effects in precisely the same way as the
film's director and producer did during the editing of the soundtrack in
the studio's dubbing room. In other words, the THX standard has been
created to preserve the artistic expressions in films. The Home THX standard extends the THX principles to domestic cinemas and
Home Entertainment installations, still with the intent of reproducing
films just like the directors and producers wanted the sound to be. The Home THX standard makes up the most detailed and demanding set of
performance specifications that has ever been established for home audio
equipment. The guiding principles behind the Home THX standard are as follows:
First of all, a Home THX certified system should be able to
reproduce film soundtracks at very loud, realistic levels, without audible
distortion, compression or noise. This part of the specification set calls
for powerful amplifiers and loudspeakers with extended bandwidth plus the
ability to deliver high sustained volume levels without causing listening
fatigue.
Secondly, the sound stage should be experienced just like in the dubbing
room, with an intelligible, clearly focused dialogue and the background
music and all the effects in the right places. To meet this requirement,
you need a Home THX certified processor - as a standalone unit or built
into an amplifier or an receiver - with proprietary Lucasfilm circuitry
for timbre matching of the speakers plus overall optimization of the
sound.
A special part of the Home THX standard deals with the characteristics of
the speakers. To ensure a coherent sound stage upfront, the left, center
and right main speakers should be identical, sound wise. In addition, the
dispersion or directivity of these speakers should be tightly controlled.
In the vertical plane, the speakers should have a relatively narrow spread
to reduce ceiling and floor reflections that otherwise may compromise
intelligibility and make the tonal balance unpredictable. At the same
time, the speakers should have a wide horizontal spread to give several
persons the same experience of the soundtracks.
The Home THX standard finally states that the surround speakers should
have a dipole dispersion pattern that will produce a diffuse sound field
and enhance the feeling of atmosphere in film
Horn
Acoustical
coupler between a speaker unit and the air. Just like a trumpet, a horn
amplifies sound. In addition, a horn makes it easy to control the
directivity of a speaker.
Hertz:
Unit of measurement for oscillations per second (frequency).
Imaging
Psychoacoustics
term indicating to which degree a Home Entertainment system is able to
reproduce width, depth and possible height in recordings of music.
Impedance
Alternating
current resistance, measured in ohms. Indicates the degree to which the
loudspeaker draws current from the amplifier. The nominal impedance of a
loudspeaker system normally lies between 4 and 8 ohms.
Inductor
Frequency
dependent electronic component featuring an impedance that is proportional
with frequency - the higher the frequency, the higher the impedance. In
crossover networks, inductors are used, for instance, to ensure that high
frequencies do not reach woofers.
Integrated
Amplifier
An
all-in-one amplifier combining a control amplifier and a power amplifier.
Infra Red
Modulated infra red light waves are extensively used as carriers for
remote control signals for all kinds of electronic equipment.
Kapton:
Kevlar
Very strong,
light and nonresonant, woven synthetic fabric. Because of its high price, Kevlar is mainly used for advanced applications like bulletproof vests,
racing cars and diaphragms for cost-no-object speaker units.
Laserdisc
The first
optical disc medium for consumer use, developed in the early seventies by
Philips. This 30 cm (12") disc carries analogue video and digital
audio information. The high picture quality with a horizontal resolution
of more than 400 lines has made Laserdisc the preferred film format among
Home Entertainment enthusiasts.
LCR: Left, Center, Right (front speakers) in a Home Entertainment installation.
LFE
Low
Frequency Effects. Dedicated subwoofer (the "1" channel of a 5.1
channel system) signal containing the heavy bass information that is used
extensively in many films.
Line
Input/Output
Inputs
and outputs carrying line level audio signals.
Line
Level
The
analogue signal output level available from source components like CD, DVD
and Laserdisc players. Can range from 1.0 and 2.0 V RMS.
Low Pass
Filter
Electronic
network that passes low frequencies only. Prevents woofers and subwoofers
from reproducing midrange and high frequencies
Magnet
Gap
Narrow
groove in the loudspeaker unit's magnet in which the voice coil moves.
Magnetic
Shielding
Necessary
for all speakers that are designed for use in the vicinity of CRT TV sets.
(CRT is short for Cathode Ray Tube - the type of picture tube used in all
conventional TV sets and some video projectors). Without magnetic
shielding, a loudspeaker can create severe distortions of the picture
geometry and colors.
MDF
Medium Density Fiberboard. Similar to conventional chipboard, but much
finer and rolled under high pressure. A heavy and resonance dampening
panel very suitable for the manufacturing of loudspeaker cabinets.
MIR
Magnetic
Interference Reduction.
This technique is used in front loudspeakers for surround sound to prevent
any discoloration of the TV screen when the speakers are placed close to
the TV. MIR is used in the production process where front loudspeakers are tested
for magnetic radiation.
The magnetic strayfield is controlled by mounting
small magnets on the back of the drive units, thus canceling the magnetic interference
and allowing the speakers to be placed close to a TV screen without any
problems.
Motional
Feedback
A
highly advanced servo circuit controlled by feedback from a miniature
accelerometer mounted on the woofer dust cap, compares the driver's motion
to the input signal and compensates for any deviation from the original
waveform. Motional feedback makes it possible to design a compact
subwoofer with a linear, low distortion reproduction of the lowest audible
frequencies.
MPD
Midrange Phase
Diffusion.
A new technology used in the high-end surround speakers is MPD which
ensures a superb reproduction of the surround channel.
The technique is closely related to a dipole loudspeaker and its diffuse
and spacious sound reproduction which gives you the impression of really
being in the
middle of the action.
The disadvantage of most dipole speakers is poor deep bass reproduction
due to cancellations between the two closely placed woofers.
Using the MPD technology, a 2-way system will reproduce the full frequency
area while the full range driver "shoots" in the other direction
to create the diffuse sound
picture.
The diffuse sound occurs by filtering a single full range driver, so that
it only plays in the midrange area where the human ear is best at locating
the direction of sound.
In this area, the full range driver operates in opposite phase with the
2-way system and simply destroys the ability of the human ear to locate
the speakers giving
"diffuse surround sound" without loosing any bass information.
The MPD technique thus eliminates the "Surround Sound in a Box"
effect. You simply cannot localize the surround speakers, just like in a
real cinema.
MPEG2
Audio
Motion
Pictures Expert Group proposed standard for a 5.1 channel sound system for
European DVDs.
MPEG2
Video
Motion
Pictures Expert Group standard for DVD video compression. This technique
makes it possible to store a feature film on one side of a 12 cm optical
disc.
Multimedia
General
term for equipment that is able to work with more than one medium.
Typically used in connection with PCs equipped with CD drives and sound
card.
Natural
Resonance
Structural
resonance in a material. At one or more frequencies, almost any material
will resonate when struck or subjected to other mechanical influences.
This frequency depends on the shape, weight and rigidity of the material.
In loudspeakers, there are intentional and/or unavoidable system resonance such as the natural resonance of the loudspeaker diaphragm.
Other resonance, e.g.. in the loudspeaker cabinet or the diaphragm material
are unintentional and should be reduced as much as possible.
NCC: Non
Coloration Compound. Patented, Jamo proprietary material based on a
mixture of quartz sand and a resonance dampening binder, cast between two
synthetic shells. An NCC baffle is more resonance "dead" than a
concrete tile. Yet, it may be cast into any desired shape, and its density
is 2-3 times that of wood.
Neodymium
Magnetic
alloy with about ten times the strength of conventional ferrite. Neodymium
makes it possible to design very efficient and compact magnet systems,
especially for tweeter units.
NICAM
Near Instantaneously Companded Audio Multiplexing. Digital stereo sound
system for TV transmission that is used in most European countries.
Capable of almost CD sound quality.
NTSC
National Television Standards Committee. The name of the color TV system
used in the USA and Japan.
Ohm: Unit of
measurement for electrical resistance.
Operating
Power
The
amount of amplifier power necessary to achieve a sound pressure level of
96 dB from a loudspeaker, at a distance of one meter. The lower the
operating power, the louder the speaker will play with the same amplifier.
See also Sensitivity.
OSD
On0Screen Display. Messages and/or menus on the TV screen. An increasing
number of Home Entertainment components are operated by means of a visual
OSD interface.
PAL
Phase
Alternation by Line. The name of the color TV system used in most of
Europe and several other countries.
Passive
Radiator
An
auxiliary woofer diaphragm without magnet or voice coil. Works as an extension of the primary, active woofer to improve the low frequency
reproduction.
Phase
Delay
Time
delay of some frequencies in relation to others. Normally undesirable.
Phase
Linearity: Reproduction
without phase delay.
Phase
Plug
A bullet
shaped metal or plastic "nose" mounted in the center of a
compression driver. A phase plug is able to lineralize the frequency
response and improve the dispersion of higher frequencies. Please also see
bullet.
Phono
Plug (and socket)
A basically cheap, coaxial plug that is extensively used on cables
carrying audio and composite video signals to/from Home Entertainment
equipment.
Pistonic
Ideal
state for a speaker unit. The entire diaphragm oscillates like a piston,
as one body without any tendency to breakup. Pistonic movements only occur
in the lower part of a speaker unit's frequency range.
Polymer: Chemical
compound.
Polypropylene
Strong,
relatively light and mechanically stable synthetic material. Much used for
diaphragms of better woofer and midrange speaker units.
Power
Electrical
energy, such as the output from an amplifier used to drive a speaker.
Measured in watts.
Power
Amplifier
An
amplifier which accepts a low level signal and raises its amplitude as well
as its current to a level sufficient to drive a loudspeaker.
Power
Handling Capacity
The amount of electrical power that a speaker is able to withstand
without damage. Often two power handling capacity specifications are given
- short term and long term.
PushPull Coupled
Cavity
According to this principle, two woofer units are mounted in antiphase
between two chambers, a closed chamber and one with a bass reflex port.
This allows the units to work as though they were mounted in a much larger
cabinet. The PushPull Coupled Cavity principle therefore provides three
great advantages: It produces a deeper bass, efficiency is increased, and
the reproduction becomes more precise than in conventional constructions.
PushPull
Coupling
Two
woofer units are mounted with their diaphragms facing each other. This
allows the two units to act as one heavier, more rigid unit providing
higher efficiency and cleaner bas
RCA
Originally
short for Radio Corporation of America. Common name for a coaxial phono
plug. See Phono Plug
Rear
Speakers
In a
Home Entertainment system, the speakers that reproduce off screen film
effects and ambience from the soundtrack.
Receiver: Amplifier
with built-in radio tuner.
Reflex
Loading
Venting
a loudspeaker enclosure by means of a tube or port. Reflex loading is
often used to extend the low frequency response and increase the
efficiency of a speaker system.
Resistor
Component
that reduces current in an electronic circuit. Resistance is
measured in ohms.
RF: Radio
Frequency - any frequency above 30 kHz.
RMS
Root
Mean Square - the true, effective power generated by an electrical
circuit. The RMS output power of an amplifier is typically defined as its
continuous power capacity measured at 1 kHz with less than 1% THD.
Satellite
Loudspeakers
Loudspeakers
which are used as side loudspeakers in a subwoofer system. Satellite
loudspeakers reproduce only treble and midrange tones, which means that
their size can be significantly reduced in comparison with complete
speaker systems.
SCART
Syndicate des Constructer d'Appareils Radio Récepteurs et
Téleviseurs.
Common name for Euroconnector. A European 21pin plug and socket system
used to connect TV sets with all kinds of source equipment like VCRs,
satellite receivers, DVD and Laserdisc players.
SECAM
Séquentiale
Couleur à Mémoire. The name of the color TV system used in France and a
few other countries.
Sensitivity
The
sound pressure level, expressed in dB, which is measured at a distance of
one meter right in front of the loudspeaker when it receives 1 watt from
the power amplifier. See also Operating power.
Soft
Dome
A dome
loudspeaker diaphragm made from a soft material such as woven or processed
synthetic fabric.
Software
A general
term covering all kinds of data and audio/visual information. See also
Hardware.
Sound
Field
The
perceived acoustics (width, depth and reverberation) experienced during
audio reproduction.
Soundtrack
The part
of a film that contains all the audio information - dialogue, background
music and sound effects.
Spike
Spiked
loudspeaker foot made from steel or other hard metals. Spikes are used
extensively under HiFi speakers to act as an interface between the cabinet
and the floor. On carpeted floors, spikes are able to penetrate a soft
carpet and couple the cabinet mechanically to the wooden or concrete
understructure. Often quoted benefits from using spikes include improved
imaging and a "firmer" sound.
SPL
Sound
Pressure Level. In audio, the level of loudness produced by the speakers,
and measured in dB. An SPL of 95 dB is considered loud by most people,
while 115 dB and higher may cause listening fatigue and hearing damage.
Stereo:
Two channel
audio recording and reproduction.
Stereo
Imaging
Three
dimensional information in a stereo reproduction with two loudspeakers.
Good loudspeakers can, besides the perspective provided as a result of the
sound source's location, also reproduce depth, height and width in the
audio image. The ideal is that the loudspeakers "disappear" in
the audio image.
Subwoofer
Dedicated
low frequency bass loudspeaker, often mounted in a separate cabinet that
may also contain a power amplifier with signal processing circuitry
(active subwoofer). The typical subwoofer frequency range lies below 200
Hz or less where the human ear is almost non- directional. This makes it
possible to position a subwoofer almost anywhere in the room, and still
enjoy deep notes and powerful, rumbling film effects.
Super
VHS
Improved high band version of the basic VHS video format offering higher horizontal
resolution (about 400 lines) and better colors. Super VHS tapes are very seldom used as carriers for prerecorded video software.
Terminal
In this
context, the connectors on amplifiers and loudspeaker cabinets for speaker
cable.
Test
Signal
Most
surround equipment can produce a noise signal as an aid to adjust the
level of each channel. Unless the processor features auto calibration, the
adjustment has to be performed by listening or the use of a sound pressure
level meter.
THD: Total
Harmonic Distortion. The sum of all harmonic distortion products.
THX
Named after
Lucas' first feature film, THX 1138. A set of technical specifications,
developed by Lucasfilm, for high quality dubbing studios and cinema
acoustics. See Home THX.
Transformer
An
electrical device that changes the voltage and current of a signal without
altering its power. Used for power supplies and impedance matching.
Transient:
In this
context, a burst of energy.
Treble
The upper
portion of the audible frequency range.
Tweeter: Dedicated
high frequency loudspeaker unit.
Volt: The unit of measurement for electrical tension.
VHS
Video
Home System. The universally adapted video format for home use. VHS was
introduced in 1977 and is beginning to show its age. With a horizontal
resolution of only about 240 lines, the picture quality is just adequate
for nondemanding applications.
VHS HiFi
The basic
VHS video format with the addition of stereo sound in near CD quality.
Voice
Coil
Coil of
very thin wire wound around a former mounted on the back of the
loudspeaker diaphragm. The voice coil is located in a gap in the
loudspeaker unit's magnet and when a current is passed through it, a
magnetic field is created which, depending on the direction of the current
through the coil, is attracted or repelled by the fixed magnet. This is
the reason why the diaphragm moves backwards and forwards. The voice coil
is the "heart" of the loudspeaker unit's "motor".
Watt: The unit of measurement for electronic power.
Woofer: Dedicated
low frequency loudspeaker
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