MOTU 1248 User Manual page 103

outside the critical frequency range of the
instrument being recorded, you can avoid phase
problems among the mic signals.
Tuning PA systems
The Phase Analysis window can also be used to
troubleshoot and tune PAs and sound
reinforcement systems by placing microphones in
strategic locations, comparing the two signals in
the Phase Analysis grid and looking for phase
issues at various locations.
Summing to mono
The Phase Analysis window is ideal for checking
stereo audio that needs to be summed to mono.
The Phase Analysis lets you see what frequencies
will be canceled out when summed.
In the rectangular view, any lines in the signal that
touch the +1.0 or -1.0 vertical lines in the grid will
be canceled out at the frequency where they touch,
when the signal is summed to mono.
In the polar view, any signal that falls on the
negative y axis (below zero) will be canceled out
when the signal is summed to mono.
Perfectly in phase
Polar view
Rectangular
view
Figure 9-26: Two identical audio streams in the Phase Analysis.
M O T U A U D I O T O O L S
Checking for phase issues in stereo tracks
You can use the Phase Analysis window to check
the overall polarity of a stereo mix. Figure 9-27 is
an example of a full stereo mix that has phase
issues, as indicated by the majority of the signal's
energy, which is predominantly skewed to the left
side of the rectangular view (left) and spread along
the -y axis in the polar view (right).
Figure 9-27: A stereo mix with phase issues.
One-sample delay Twenty-sample delay Inverted
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