Rockford Fosgate AF/4HD, Руководство по установке

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SUMMING CHANNEL
The Summing Channel can be defined as summed or non summed by moving the jumper
switchers to the summed or non summed positions. (See diagram below)
PHASE SHIFT AND CANCELLATION
The filter sections used in crossovers (both active and passive) change the phase of the input
signal as well as the amplitude. In effect, phase shift moves the output forward or backward
compared to the input. Phase shifting is measured in degrees. One full cycle is 360°, so
if the
output signal moves back 1/4 cycle, the phase shift is 1/4 of 360°, or -90°.
Cancellation is what happens when one speaker is pushing while the other is pulling. Instead
of putting out sound into the environment, the speakers just swap air back and forth. (This is what
happens when stereo speakers are hooked up out of phase).
The phase shift of crossover filters can cause cancellation. The drawing of the 90° leading and
lagging waveforms above shows that the leading wave is negative when the lagging wave is
positive. If each output went to a speaker, the speakers would be out of phase and cancellation
would occur.
The Phase shift at Cutoff table shows that 12dB/Octave filters have +90° and -90° phase shifts
at cutoff, and therefore they will produce cancellation unless something is done.
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