Meridian Audio 861 - Manual (Page 32)

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DSP Presets DSP presets for two-channel material
The digital surround controller provides several signal
processing options for two-channel material. The Music
DSP presets are designed for use with music from
sources such as CD or radio:
Music, Trifield, Ambisonics, Super Stereo, Music
Logic, PLIIx Music, Stereo, and Direct.
The Logic DSP presets are designed for use with film
soundtracks or TV programmes:
PLIIx Movie, PLIIx THX, TV Logic, and Mono.
The Music and Logic DSP presets use the Music and
Logic speaker layout respectively; see
Speaker layouts,
page 5.
Music
The Music DSP preset extracts the mono and
surround components of the original recording. These
components provide an alternative representation of
the original sound, and this is sometimes used for
recording systems or in broadcasts such as FM radio.
The mono element is equalised using a proprietary
Meridian technique to match the tone colour of the
centre speaker, and to compensate for the fact that the
frequency response of human hearing changes with
direction.
The Music DSP preset is recommended for recordings
made with spaced omnidirectional microphones, or
using a mono-surround technique.
Trifield
As for the Music DSP preset, the Trifield preset
extracts the mono and surround components of the
original recording. It then calculates the signals for the
front, left, centre, and right speakers, using the phase
and amplitude differences between the three front
channels, to redistribute the sounds on a frequency-
dependent basis.
This gives a significant improvement over traditional
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•
stereo, which converts the differences between the
microphone signals into amplitude differences in the
speaker signals. This version of the Trifield algorithm is
virtually impossible to implement without digital signal
processing.
Trifield is recommended for well-made recordings
and stereo television broadcasts that are not Dolby
Surround encoded. An advantage over the Music DSP
preset is that the front stereo image is more focused,
and the width of the image can be adjusted.
Music and Trifield DSP preset
parameters
Parameter Options What it changes
Centre Flat, EQ1–3 The timbre of the centre
loudspeaker.
Width† 0–1.5 The width of the image.
Surr. Rear Surr. Rear,
Surr. Side,
Surr. All Switches the surround
signal between the side
and rear speakers.
R Filter Off, 1kHz,
3kHz, 7kHz The cutoff of high
frequencies from the
rear surrounds.
S Filter Off, 1kHz,
3kHz, 7kHz The cutoff of high
frequencies from the
side surrounds.
† Trifield only.
Ambisonics
The Ambisonics DSP preset can decode two-channel
UHJ format, the stereo-compatible surround encoding
found on Ambisonically-recorded discs and broadcasts.
This material is specifically encoded for surround
reproduction and can give breathtakingly realistic sound
when replayed using the digital surround controller.