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Damping
- Of or pertaining to the control of vibration by
electrical or mechanical means.
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Damping
Material - Any material that absorbs sound
waves and eliminates acoustic energy by converting it
into a different form. Fibrous material, for example,
turns acoustic energy into heat via friction.
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D'Appolito - Vertically symmetrical driver
array. Typically consists of a tweeter mounted between
two woofers. Creates a more-vertically directional
sound with evenly spaced lobes in the off-axis response
when compared with asymmetrical driver arrays.
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DBS
- Abbreviation for Direct Broadcast Satellite. Term
that replaced DSS to describe small-dish, digital
satellite systems such as DirecTV and Dish Network.
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Decibel
(dB) - A logarithmic measurement unit that
describes a sound's relative loudness, though it can
also be used to describe the relative difference between
two power levels. A decibel is one tenth of a Bel. In
sound, decibels generally measure a scale from 0 (the
threshold of hearing) to 120-140 dB (the threshold of
pain). A 3dB difference equates to a doubling of power.
A 10dB difference is required to double the subjective
volume. A 1dB difference over a broad frequency range
is noticeable to most people, while a 0.2dB difference
can affect the subjective impression of a sound.
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Delay
- The time difference between a sonic event and its
perception at the listening position (sound traveling
through space is delayed according to the distance it
travels). People perceive spaciousness by the delay
between the arrival of direct and reflected sound
(larger spaces cause longer delays).
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Diaphragm - The part of a dynamic loudspeaker
attached to the voice coil that produces sound. It
usually has the shape of a cone or dome.
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Diffusion - In audio, the scattering of sound
waves, reducing the sense of localization. In video,
the scattering of light waves, reducing hot spotting, as
in a diffusion screen.
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Diffusor
- Acoustical treatment device that preserves sound
energy by reflecting it evenly in multiple directions,
as opposed to a flat surface, which reflects a majority
of the sound energy in one direction.
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Digital
Audio Server - Essentially a hard drive, a
digital audio server stores compressed audio files (like
MP3 or WMA). Most include the processing to make the
files, and all have the ability to play them back.
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Digital
Coaxial Connection - A digital coaxial
connection refers to a wired connection that is used for
transferring digital audio signals (such as PCM, Dolby
Digital, and DTS) from a source device, such as CD or
DVD player and an AV receiver or Surround Sound
Preamp/Processor. Digital Coaxial Connections use
RCA-style connection plugs.
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Digital
Optical Connection - A digital optical
connection refers to a fiber-optic connection that is
used for transferring digital audio signals (such as
PCM, Dolby Digital, and DTS) from a source device, such
as CD or DVD player and an AV receiver or Surround Sound
Preamp/Processor.
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Digital
Theater Systems - See DTS.
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D-ILA
- Abbreviation for Direct Drive Image Light Amplifier.
This Hughes/JVC technology uses a reflective LCD to
create an image. A light source is then reflected off
the reflective LCD and is directed through a lens to a
screen.
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Dipole
- Speakers with drivers on opposite faces that are wired
electrically out of phase, creating an area of
cancellation to the sides. Recommended by THX for use
as surround speakers, with null directed at the listener
to create a more ambient and non-localizable effect.
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Direct-Stream Digital - A format for encoding
high-resolution audio signals. It uses a 1-bit encoder
with a sampling rate of 2,822,400 samples per second
(verses 44,100 for CD), and used to encode six
high-resolution channels on SACD.
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Direct-View Television - Display whose image
is created on the surface from which it is viewed.
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Dispersion - The spread of sound over a wide
area.
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Distortion - Any undesired change in an audio
signal between input and the output.
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DLP
- Abbreviation for Digital Light Processing. A Texas
Instruments process of projecting video images using a
light source reflecting off of an array of tens of
thousands of microscopic mirrors. Each mirror
represents a pixel and reflects light toward the lens
for white and away from it for black, modulating in
between for various shades of gray. Three-chip versions
use separate arrays for the red, green, and blue colors.
Single-chip arrays use a color-filter wheel that
alternates each filter color in front of the mirror
array at appropriate intervals.
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DMD
- Abbreviation for Digital Micromirror Device. Texas
Instruments engine that powers DLP projectors. Uses an
array with tens of thousands of microscopic mirrors that
reflect a light source toward or away from the lens,
creating an image. Each mirror represents a pixel. See
DLP.
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DNR
- Abbreviation for Dynamic Noise Reduction. A
signal-processing circuit that attempts to reduce the
level of high-frequency noise. Unlike Dolby NR, DNR
doesn't require preprocessing during recording.
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Dolby B
- A noise-reduction system that increases the level of
high frequencies during recording and decreases them
during playback.
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Dolby C
- An improvement on Dolby B that provides about twice as
much noise reduction.
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Dolby
Digital - An encoding system that digitally
compresses up to 5.1 discrete channels of audio (left
front, center, right front, left surround, right
surround, and LFE) into a single bitstream, which can be
recorded onto a DVD, HDTV broadcast, or other form of
digital media. When RF-modulated, it was included on
some laser discs, which requires an RF-demodulator
before the signal can be decoded. Five channels are
full-range; the .1 channel is a band-limited LFE track.
A Dolby Digital processor (found in most new receivers,
preamps, and some DVD players) can decode this signal
back into the 5.1 separate channels. Most films since
1992's Batman Returns have been recorded in a 5.1
digital format, though a number of films before that had
6-channel analog tracks that have been remastered into
5.1.
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Dolby EX
- An enhancement to Dolby Digital that adds a surround
back channel to 5.1 soundtracks. The sixth channel is
matrixed from the left and right surround channels.
Often referred to as 6.1. Sometimes referred to as 7.1
if the system uses two surround back speakers, even
though both speakers reproduce the same signal.
Software is backwards-compatible with 5.1 systems, but
requires an EX or 6.1 processor to obtain additional
benefit.
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Dolby
Pro Logic - An enhancement of the Dolby
Surround decoding process. Pro Logic decoders derive
left, center, right, and a mono surround channel from
two-channel Dolby Surround–encoded material via matrix
techniques.
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Dolby
Pro Logic II - An enhanced version of Pro
Logic. Adds improved decoding for two-channel,
non-encoded soundtracks and music.
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Dolby
TrueHD - Dolby TrueHD is a high definition
digital-based surround sound format that supports up to
8-channels of surround decoding and is bit-for-bit
identical to a studio master recording. Dolby TrueHD is
one of the several audio formats designed and employed
by Blu-ray Disc and HD-DVD technologies. Dolby TrueHD
is compatible with the audio portion of the
HDMI interface. For more technical details, go to
the
official Dolby TrueHD page.
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Dome
- A type of speaker-driver shape; usually used for
tweeters (convex). Concave domes are usually referred
to as "inverted domes."
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Dope
- A tacky substance added to paper cones to damp
spurious vibrations that can cause breakup and rough
response. Also, see Editor.
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Dot
Crawl - An artifact of composite video
signals that appears as a moving, zipper-like, vertical
border between colors.
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Driver
- A speaker without an enclosure; also refers
to the active element of a speaker system that creates
compressions and rarefactions in the air.
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DSD
- Abbreviation for Direct Stream Digital.
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DSP
- Abbreviation for Digital Signal Processing.
Manipulating an audio signal digitally to create
various possible effects at the output. Often refers to
artificially generated surround effects derived from and
applied to two-channel sources.
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DTS
- Abbreviation for Digital Theater Systems. A digital
sound recording format that was originally developed for
theatrical film soundtracks, starting with Jurassic
Park. Records 5.1 discrete channels of audio onto a
handful of laser discs, CDs, and DVDs. Requires a
player with DTS output connected to a DTS processor.
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DTS ES
- An enhanced version of the 5.1 DTS system. Like
Dolby's Surround EX, a sixth channel is added. In some
cases (DTS ES Discrete), the sixth channel is discrete.
Software is backwards-compatible with 5.1 systems, but
requires an ES or 6.1 processor to obtain additional
benefit. Neo:6 is a subset of DTS ES that creates 6.1
from material with fewer original channels.
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DTV
- Abbreviation for Digital Television.
Umbrella term used for the ATSC system that will
eventually replace our NTSC system in 2006. HDTV is a
subset of the DTV system. While the FCC does not
recognize specific scan rates in the adopted DTV system,
typically accepted rates include 480i, 480p, 720p, and
1080i.
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Dual
Disc - Dual Disc is a controversial new
format that is a disc with a DVD layer on one side and a
CD-type layer on the other. Since the disc has a
slightly different thickness than either a standard DVD
or standard CD, it may not have complete playback
compatibility on some DVD and CD players.
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D-VHS
- Abbreviation for Digital VHS. Digital
signals recorded onto magnetic tape. Greater capacity
than typical VHS; can record compressed HDTV signals.
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DVD
- Officially known as the Digital Video Disc, though
marketers unofficially refer to it as the Digital
Versatile Disc. DVD uses a 5-inch disc with anywhere
from 4.5 Gb (single layer, single-sided) to 17 Gb
storage capacity (double-layer, double sided). It uses
MPEG2 compression to encode 720:480p resolution,
full-motion video and Dolby Digital to encode 5.1
channels of discrete audio. The disc can also contain
PCM, DTS, and MPEG audio soundtracks and numerous other
features. An audio-only version, DVD-A uses MLP to
encode six channels of 24-bit/96-kHz audio.
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DVD-A
- Abbreviation for Digital Versatile Disc-Audio.
Enhanced audio format with up to six channels of
high-resolution, 24-bit/96-kHz audio encoded onto a DVD,
usually using MLP lossless encoding. Requires a DVD-A
player and a controller with 6-channel inputs (or a
proprietary digital link) for full compatibility.
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DVD-R
- A recordable DVD format similar to CD-R in that it is
a write-once medium. Backed by Pioneer, Panasonic,
Toshiba, and others.
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DVD-R DL
- DVD-R DL is a record-once format that is identical to
DVD-R, except that it has two layers on the same side of
the DVD. This allows twice the recording time capacity
on a single side. This format is being incorporated
slowly on some newer DVD Recorders.
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DVD-RW
- A recordable DVD format similar to CD-RW in that it is
re-recordable medium. Backed by Pioneer, Panasonic,
Toshiba, and others.
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DVD+R
- A recordable DVD format similar to CD-R in that it is
a write-once medium. Backed by Sony, Philips, Yamaha,
HP, and others.
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DVD+RW
- A recordable DVD format similar to CD-RW in that it is
re-recordable medium. Backed by Sony, Philips, Yamaha,
HP, and others.
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DVD-RAM
- A recordable DVD format similar to DVD-RW in that it
is a re-writeable format. Unlike DVD-RW it is capable
of being written to and erased over 100,000 times.
Backed by Hitachi, Panasonic, Toshiba, and others.
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DVI
- Abbreviation for Digital Visual Interface. Connection
standard developed by Intel for connecting computers to
digital monitors such as flat panels and DLP projectors.
A consumer electronics version, not necessarily
compatible with the PC version, is used as a connection
standard for HDTV tuners and displays. Transmits an
uncompressed digital signal to the display. The latter
version uses HDCP copy protection to prevent
unauthorized copying.
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DVR
- Abbreviation for Digital Video Recorder. A DVR is
a video recording device that records on a hard disk
drive, rather than on video tape or disc. DVRs can be
incorporated into cable and satellite boxes, as well as
an addition to a standalone DVD recorder. DVR use may,
or may not, be paired with a paid subscription
requirement. A DVR is also sometimes referred to as a
PVR (Personal Video Recorder).
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Dynamic
Compression - Dynamic Compression is a term
applied to a feature on many Home Theater Receivers, DVD
players, and some televisions that enables the consumer
to change the relationship between the loudest parts of
the soundtrack and the quieter parts of the soundtrack
when you are playing a DVD or TV program. In other
words, if you find that the explosions or other loud
parts are too loud and things such as dialog is too
soft, by changing the dynamic compression setting, you
can make it so the sounds of the explosions are not
quite as loud and the dialog will sound louder. This
makes the overall sound more even. This is especially
useful when playing a DVD at low volume.
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Dynamic
Headroom - Dynamic Headroom refers to the
ability of a receiver or amplifier to output power at a
significantly higher level than normal for short periods
to accommodate musical peaks or extreme sound effects in
films. This specification is important in home theater,
where extreme changes in volume occur during the course
of a film. Dynamic Headroom is measured in Decibels.
If a receiver/amplifier has the ability to double is
power output for a brief period to accommodate the
conditions described above, it would have a Dynamic
Headroom of 3db
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Dynamic
Range -
The difference between the lowest and the highest
levels; in audio, it's often expressed in decibels. In
video, it's listed as the contrast ratio.
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