5.1 Surround Sound - The digital audio
multichannel format developed by the Moving Picture Experts. IT refers
to the five discrete, full bandwidth (20-20kHz) channels - left, right,
& center fronts, plus left & right surrounds - and the ".1" usually
refers to the limited bandwidth (20-120Hz) subwoofer channel.
AC-3 (audio coding 3)- Dolby's digital audio
data compression algorithm adopted for HDTV transmission and used in
DVDs, laserdiscs and CDs for multichannel home theater use. Also see:
Acoustics- The science or study of sound.
Ambient Noise- The sound that exists in a room that does not come from a
loudspeaker, musical instrument or some other intentional sound source.
A person speaking to an audience is not ambient noise, etc.
Amplifier- A device which increases signal level. Many types of
amplifiers are used in audio systems. Amplifiers typically increase
voltage, current or both.
Aspect Ratio- Ratio of a picture's width to its height. Typical
television aspect ratio is 4:3, while wide screen formats provide
greater width of the viewing area.
Audio frequency- The acoustic spectrum of human hearing, generally
regarded to be between 20 Hz and 20 kHz.
Bandwidth- The range of frequencies
reproduced by an amplifier or transducer.
Bipolar- Type of loudspeaker with drivers mounted on opposite sides of
the cabinet, or speaker enclosure. Drivers move in and out together so
they remain "in-phase." Used as rear-surround speakers; better when
placed closer to the listener. (Also see dipolar)
Coax- Short for Coaxial cable - a type of 75
ohm cable most commonly used for Cable TV connections and with some
antenna systems for FM radio and Television. Also used to connect CD or
DVD transports to DACs. May also be found as the basis for many video
interconnect cables including composite, s-video, component, and RGB.
Component video- A video signal transfer method utilizing three cables
which separate the three parts of a video signal: Luminance (Y) is the
black & white, pR and PB are the separate portions of the Chrominance,
or color signal. Component Video, properly implemented, should provide
the best possible image quality on TV monitors that support it.
DAC- A Digital to Audio Converter. Converts
a digital bitstream to an analog signal. Can be a separate "box" that
connects between a CD Transport or CD Player and a pre-amplifier.
Damping- The reduction of movement of a speaker cone, due either to the
electromechanical characteristics of the speaker driver and suspension,
the effects of frictional losses inside a speaker enclosure, and/or by
Decibel- Essential acoustics measurement; a unit of sound used to
measure the relative differences between sounds. Equal to one-tenth of a
bel, the amount of energy in the form of sound that is transmitted to
one square centimeter of the ear. One dB is considered to be the
smallest change in sound that is perceptible to the human ear.
Distortion- Audio distortion: a measure of unwanted signals; the name
given to anything that alters a pure input signal in any way other than
changing its size. The most common forms of distortion are unwanted
components or artifacts added to the original signal, including random
and hum-related noise.
Dolby Digital- A five-channel system consisting of discrete left,
center, right and left rear, right rear channels. The AC3 standard also
has a separate subwoofer channel for the lowest frequencies.
DTS- Digital Theater Systems (www.dtstech.com/). DTS is an
international, digital technology company specializing in multichannel
audio for entertainment. DTS Digital Surround is an encode/decode system
that delivers six channels (5.1) of master-quality, 20-bit audio
DTV- Digital TV. A new system of digital television broadcasts.
DVD- Originally coined as Digital Video Disc or then changed to Digital
Versatile Disc, upon adoption by the computer industry. DVD has the same
physical dimensions of a CD, however it can hold much more information.
Efficiency- The loudspeaker parameter that
gives the level of sound output when measured at a prescribed distance
with a standard level of electrical energy fed into the speaker. Often
expressed as decibels/watt/meter (dB/w/m).
EQ (Equalizer)- Electronic device that acts as active filters used to
boost or attenuate certain frequencies.
HDTV- The highest rung in the ladder of
various DTV formats. Three determining factors delineate HDTV: 1080
active scan lines, 16:9 widescreen ratio, and Dolby Digital sound.
Home Theater In A Box (HTiB)- Any of several kinds of packaged
audio-for-video systems designed to create an "instant" home theater;
usually inexpensive and compact. Typically includes a multi-speaker
complement plus a receiver or multichannel amplifier to drive the
speakers. May function as a stand-alone 5.1-channel system or may be
designed to add channels to an existing stereo or other audio system.
Imaging- the speaker's ability to localize
different instruments playing simultaneously.
In-Wall Speakers- Speakers designed to mount flush within a wall.
Magnetically Shielded- A type of loudspeaker
in which the electromagnetic field created by the driver magnets - which
can discolor a TV picture and potentially ruin a tube - is contained.
Midrange- The mid band of an audible signal, typically anywhere between
350 Hz and 3 kHz. Also refers to those specific frequencies as well.
NTSC- National Television System Committee.
The NTSC standard has a fixed vertical resolution of 525 horizontal
lines. There are 60 fields displayed per second. A field is a set of
even lines, or odd lines. The odd and even fields are displayed
sequentially, thus interlacing the full frame. One full frame,
therefore, is made of two interlaced fields, and is displayed about
every 1/30 of a second. See also interlaced.
RCA Connector- Standard pin plug or jack
used to connect audio and video components, developed by RCA
Laboratories. Also known as a phono plug or jack, even when applied to
Soundstage- Listening term. Perceived width,
depth, and height of music (or sound) especially for stereo
reproduction. A set of speakers with good soundstaging means you can
localize a separate position for each instrument and voice, emulating a
Stereo- Derived from the Greek word meaning solid. Two channel audio
format. However, the purpose of stereo is not to give you separate right
and left channels, but to provide the illusion of a three-dimensional,
holographic image between the speakers.
Subwoofer- A speaker designed exclusively for low-frequency
reproduction. A true subwoofer should be able to at least reach into the
bottom octave (20-40Hz). They are usually contained in their own
enclosure and can be placed anywhere in a listening room due to the fact
that low frequencies cannot be localized or pinpointed.
S-VHS- Super VHS. A recording and playback format requiring an SVHS VCR.
As the name implies, it's better than standard VHS, producing about 480
lines of resolution. (Standard VHS displays about 240 lines.)
THX- Tomlinson Holman Experiment. THX is a
set of technical standards and performance criteria developed by
Lucasfilm to ensure that moviegoers see and hear a film at optimum
performance levels, "as the director intended". This comprehensive set
of standards includes rigorous specifications designed to optimize
equipment, room acoustics, background noise levels, and projection and
Tweeter- Transducer responsible for reproducing the higher frequencies
of an audible signal, typically active above 3 or 4 kHz.
Watt- A unit of electrical power. A watt of
electrical power is the use of one joule of energy per second. Watts of
electrical power equals volts times amperes.
Widescreen- In home theater, a viewing aspect ratio wider than 4:3
(which is the typical television ratio). There are various widescreen
formats, one of which is 16:9.
Y-adapter- Any type of connection that
splits a signal into two parts. An example would be a connector with one
female RCA jack on one end, and two male RCA jacks on the other end.