It is pretty well known that you do not want your speakers wired out of phase, and that a general rule of thumb is that if you have a subwoofer in the front and one in the rear, you will have to set the rear subwoofer 180deg out of phase with the front, generally speaking.
This is to eliminate cancellation of the sound waves. If the right front speaker is moving out, and the left speaker is moving in, there is canceling of sound, positive plus negative equals nothing. Similarly, you WANT the rear subwoofer out of phase with the front, when the front subwoofer driver is moving out, you want the rear subwoofer driver moving in, that way they work together and not against each other.
Finally my question/thought/rambling:
I am looking at building a subwoofer with a driver and a passive radiator, and want to but them both on the front face of the cabinet (ok I am looking at stealing the North Creek design for the Peerless 12” XLS driver and passive radiator) . The Passive radiator is a slave to the driver, it only gets it’s movement from the drivers movement, so when the driver moves out, the PR moves in.
How does this not cause cancellation?
Many here own early Polks that use a PR design, same question.
And if you own SDA’s, man what a mess, they use a PR, I have the same question as above but add to it, the SDA drivers are out of phase with the stereo drivers, so you have stereo drivers in phase, PR out of phase with the stereo drivers, and a PR that is out of phase with the stereo drivers, but in phase with the SDA drivers, my head hurts!