Stereo Analyze; Signal Metering And Channel Summation Utility Algorithm - Kurzweil K2661 Musician’s Reference Manual

KDFX Reference
KDFX Algorithm Specifications

999 Stereo Analyze

Signal metering and channel summation utility algorithm

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Stereo Analyze is a utility algorithm which provides metering of stereo signals as its primary function. In
addition to metering, the gains of the two channels are separately controllable, either channel may be
inverted, and sum and differences to the two channels may be metered and monitored. If you use this
algorithm with Live Mode, you can obtain a significant amount of information not only about your own
mix, but of any recording you have in your library.
There are separate meters for the left and right output channels. Two types of meters are provided: peak
and RMS. Meter display units are decibels relative to digital full scale (dBFS). The peak meters display the
levels of the maximum signal peak that occurred during the meter update period (every 40ms). The RMS
meter displays the average power of the input signal. RMS is an abbreviation for root-mean-square, so the
signal is squared, averaged and a square root is taken. For a real-time meter, we do not take an average
over all time, but rather average past signals with a stronger weighting to signals in the recent past than
the far past. The RMS Settle parameter controls how strong the weighting is for recent signals over much
older signals. RMS Settle is expressed in units of dB/s (decibels per second), meaning how fast the RMS
meter can rise or fall with changing signal levels.
You can choose to meter and monitor normal left (L) and right (R) stereo signals, or with the Out Mode
parameters, you can select normalized sum and differences of the left and right channels. The Out Mode
parameters control the signals being passed to the outputs and to the meters: what you see on the meters
are the signals to which you are listening. The Invert parameters provide a quick polarity reversal to the
input signals. This polarity reversal occurs before sum and differences. The Invert parameters are actually
redundant since Out Mode provides signal inversions as well. The left and right Out Mode parameters
may be set to any of the following:
L
R
(L+R)/2
(L-R)/2
-L
-R
-(L+R)/2
(R-L)/2
You may well ask why you would want to meter or monitor reversals or sums or differences of your stereo
channels. One important case is to determine if your final mix is mono compatible -- very important if
your mix is ever going to be broadcast on radio or television. Set both the left and right Out Mode
parameters to (L+R)/2 to listen to the mono signal. If you find that parts of your mix disappear or start to
sound metallic (comb filtered), you may have to go back and do some work on your mix.
The difference signal (L-R)/2 provides a measure of the stereo content of your mix and can be very
indicative of mixing style. Listening to the difference signal of someone else's recordings can often
demonstrate interesting techniques (and mistakes!) in stereo production. The difference signal contains
everything that doesn't make it into the mono mix. Out of phase signals will appear only in the difference
signal. Panned signals will appear in both the sum and difference signals to varying degrees. A delay
between left and right channels will sound metallic (comb filtered or flanged) in both the sum and
difference channels. If the entire mix seems to have a relative left/right delay, you can use the L/R Delay
10-250
left channel
right channel
normalized sum of left and right
normalized difference of left minus right
polarity reversed left channel
polarity reversed right channel
polarity reversed and normalized sum of left and right
normailized difference of right minus left