AKG SURROUND
TECHNOLOGY
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Dolby Surround Pro-Logic decoder
Movie soundtracks are usually mixed
down to four channels. Left and Right
are the same two channels used for hi-
fi stereo. The third channel is the Cen-
ter channel projected from above or be-
low the video screen. The fourth channel
is called “surround” or “rear” and is usu-
ally projected by two loudspeakers
placed behind the listeners.
These four channels are encoded by a
special circuit and recorded in “piggy-
back” fashion on the two stereo tracks.
This allows the signal to be reproduced
in mono, stereo, or (using a decoder)
through four separate channels. For sur-
round reproduction, the signal needs to
be decoded. This is the job of the Dolby
Surround decoder.
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Dolby Digital decoder
The digital multi-channel format of Dolby
Laboratories, Inc. used in advanced
commercial theater equipment is the
most widespread digital surround stan-
dard for DVDs, laser discs, and digital
TV. The distinguishing feature of Dolby
Digital is that all tracks (five audio tracks
plus one subwoofer track) are stored
separately in digital form. These discreet
channels allow an optimized spatial
sound to be generated that can be
processed in the digital domain by IVA
without any degradation of sound qual-
ity.
➝
LOGIC7 decoder
Up to now, the latest development by
the innovative engineers at LEXICON
was only used in high-quality, high-end
processors. Now, the unique advan-
tages of the LOGIC7 decoder are avail-
able for headphones for the first time.
The LOGIC7 decoder automatically
identifies the input signal as mono,
stereo, or surround encoded and
processes the signals appropriately.
The LOGIC7 decoder uses the localiza-
tion cues contained in stereo signals to
generate a 3-D sound that conveys to
the listener a sense of envelopment in
the sound rather than standing in front
of a pair of loudspeakers. Surround en-
coded signals are reproduced exactly as
defined in the mix.
Along with the standard 5.1 surround
format, LOGIC7 also provides left and
right side channels, for a total of seven
loudspeaker channels plus one sub-
woofer channel.
In addition, another surround center
channel is added in the headphone
mode. In conjunction with IVA process-
ing, LOGIC7 provides its full perform-
ance level with eight virtual loudspeak-
ers.
The result is far more natural and accu-
rate imaging.
➝
IVA processing
Patented AKG IVA processing for spa-
tial sound is the heart of each HEARO
surround headphone system. IVA pro-
vides natural (binaural) imaging through
headphones in a similar way as if you
were listening to a pair or loudspeak-
ers.
Binaural sound
A:
Sound waves from a given source
arrive at one ear earlier than they do at
the other, and they “look” different, too.
Amplitude and phase shifts allow us to
localize a sound source in space.
B:
Headphones usually eliminate
these important amplitude and phase
shifts. Sound sources are perceived as
being inside the head rather than in the
room.
C:
IVA processing developed by AKG
adds to a stereo signal the amplitude
and phase shifts that are necessary to
create a sense of natural, spatial, “out-
side the head” imaging.
In short, IVA processing provides a per-
fectly natural, spatial (binaural) sound
through headphones.
➝
Digital transmission
Digital transmission ensures pristine
surround sound with a CD-level dy-
namic range and no perceptible noise.
Digital radio links are immune to inter-
ference and “jamming” from devices emitting RF radiation such as
TV sets or computers.
➝
Eight-channel surround
Eight-channel surround is an improved version of the internationally
accepted five-channel format. The new format models eight virtual
loudspeakers distributed around the room. The result is an incredi-
bly spacious sound. Eight-channel surround requires a
➝
LOGIC7
decoder.
➝
Ear matching curves
Sound waves from a given source arrive at one ear earlier than they
do at the other, (see also “IVA processing”, para A) because the head,
trunk, and ears cause amplitude and phase shifts. All these changes
can be illustrated by so-called “head-related transfer function”. Since
these curves differ from person to person, everyone perceives sound
in a different way. Ear matching curves are electronic models of outer
ear transfer curves that match the headphone’s sound to the user’s
acoustic perception.
➝
Digital antenna diversity
Diversity reception is normally used in professional wireless micro-
phone systems to ensure perfect reception even under extremely dif-
ficult conditions. An adaptive algorithm makes sure the antenna that
delivers the better signal is always active to prevent dropouts.
➝
VMAx
VMAx provides surround sound from
a pair of stereo loudspeakers, with no
extra hardware. All you need is a
stereo amplifier and speakers. The
VMAx processor simulates the en-
velopment of surround sound.
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“Dolby”,
the
“Double-D”
and
“Pro-Logic”
are trademarks of Dolby Laboratories Licencing Corporation.
Logic7 and the Logic7 Logo are
registered trademarks of Lexicon,
Inc.,
A Harman International Company
.
VMA
x
DOLBY SURROUND
®
P R O
•
L O G I C
DOLBY
®
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