Stereo Image; Stereo Enhancement With Stereo Channel Correlation Metering; Block Diagram Of Stereo Image Algorithm - Kurzweil K2600 Musician’s Reference

966 Stereo Image

Stereo enhancement with stereo channel correlation metering

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Stereo Image is a stereo enhancement algorithm with metering for stereo channel correlation. The stereo
enhancement performs simple manipulations of the sum and difference of the left and right input
channels to allow widening of the stereo Þeld and increased sound Þeld envelopment. After manipulating
sum and difference signals, the signals are recombined (a sum and difference of the sum and difference) to
produce Þnal left and right output.
L Input
R Input
Figure 10-94

Block diagram of Stereo Image algorithm

The sum of left and right channels represents the mono or center mix of your stereo signal. The difference
of left and right channels contains the part of the signal that contains stereo spatial information. The Stereo
Image algorithm has controls to change the relative amounts of sum (or center) versus difference signals.
By increasing the difference signal, you can broaden the stereo image. Be warned, though, that too much
difference signal will make your stereo image sound ÒphaseyÓ. With phasey stereo, acoustic images
become difÞcult to localize and can sound like they are coming from all around or from within your head.
A bass shelf Þlter on the difference signal is also provided. By boosting only the low frequencies of the
difference signal, you can greatly improve your sense of stereo envelopment without destroying your
stereo sound Þeld. Envelopment is the feeling of being surrounded by your acoustic environment.
Localized stereo images still come from between your stereo loudspeakers, but there is an increased sense
of being wrapped in the sound Þeld.
The Stereo Image algorithm contains a stereo correlation meter. The stereo correlation meter tells you how
alike or how different your output stereo channels are from each other. When the meter is at 100%
correlation, then your signal is essentially mono. At 0% correlation, your left and right channels are the
same, but polarity inverted (there is only difference signal). The correlation meter can give you an
indication of how well a recording will mix to mono. The meter follows RMS signal levels (root-mean-
square) and the RMS Settle parameter controls how responsive the meter is to changing signals. The ÔMÕ
part of RMS is ÒmeanÓ or average of the squared signal. Since a mean over all time is neither practical or
useful, we must calculate the mean over shorter periods of time. If the time is too short we are simply
following the signal wave form, which is not helpful either, since the meter would constantly bounce
around. The RMS Settle parameter provides a range of useful time scales.
See also the Stereo Analyze algorithm which allows you to experiment directly with sum and difference
signals.
Center Gain * 1/2
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Diff Gain * 1/2
KDFX Reference
KDFX Algorithm Specifications
L Output
R Output
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