AKG Acoustics surround headphones manual AKG Surround Technology, Dolby Digital decoder

AKG SURROUND TECHNOLOGY

A Harman International Company.

➝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.

➝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

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➝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	A
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. B

In short, IVA processing provides a per- fectly natural, spatial (binaural) sound through headphones.

➝Digital transmission

Digital transmission ensures pristine

Inc.,

processed in the digital domain by IVA without any degradation of sound qual-

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surround sound with a CD-level dy-C namic range and no perceptible noise.

are trademarks of Dolby Laboratories Licencing Corporation. Logic7 and the Logic7 Logo are registered trademarks of Lexicon,

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-

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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 aVMA

“Dolby”, the “Double-D” and “Pro-Logic”

ing, LOGIC7 provides its full perform- ance level with eight virtual loudspeak- ers.

The result is far more natural and accu- rate imaging.

stereo amplifier and speakers. The VMAx processor simulates the en- velopment of surround sound.

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