I was trying to figure out what happens to the left/right channels when you bridge a 2-channel amp to drive a subwoofer. It turns out that it combines them internally.
Here's what the manual for one amplifier says:
The California amplifiers are capable of being bridged in a mono configuration. This feature
allows you the flexibility of using the amplifier to drive a ** subwoofer or a center channel. In
this configuration the amplifier sums the right and left channel to deliver one channel (mono)
output.
Please note: in order for the amplifier to sum right and left signal information, both right and
left RCA connections must be made.
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That leads me to believe that you must use a Y-cable to feed the audio into both the left and right channels of the bridged amplifier.
