Precautions & Check - Yamaha Nexo NXAMP4X4 User Manual

APPLICATION NOTE: DRIVING THE SUB FROM THE AUX SEND
Consider the simple example of the AUX signal passing through a digital device (without
processing) that is adding a delay of 2ms due to its conversion time. The AUX is then sent
to a CD12 sub while the MAIN is send to the S850 rig. The first graph display the phase
around the crossover point (85Hz in this case)
The two overlapping phases are those of the CD12 and S805 as they should be. The bellow
curve is the same as the above one with a 2ms delay.
On the magnitude graph display the difference between the well aligned system and the
one with the CD12 2ms delayed. The difference is 2dB at 100Hz. This example is displaying
the consequences of a slightly incorrect alignment. If we add to this the delay introduced
by a slightly different electric path plus the "small" delay introduced by some processing,
plus an EQ filter done by the user near the cut off frequency...The graph above could shows
differences in excess of 6dB. (Up to the point where the system might work better if you
reverse the polarity of the sub!)
Precautions & check
Before using the AUX send of your desk ensure that the outputs are in phase (you can feed
a 100Hz signal at the input and monitor the MAIN and AUX on a dual trace scope)
Always apply EQ or processing to all signals feeding the NXAMP. So the phase relation is
not affected.
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