I have the 9.1 alpine.
I replace my 3 dash with JBL. I tested each stock speaker with the app "polarity checker" (android) and found the right and left to be positive phase and the center to alter between in and 180 out depending on what frequency the app was checking. I checked the rear overhead speakers and they matched the primary phase of the fronts.
The front speakers themselves I checked with a battery to verify the positive terminal (since there is no indication or spade size difference). They were wired correctly as the commonly circulated wiring diagram here shows which verified my previous polarity findings (excluding the center that seemed to change phases, which it cant!).
The issue with these speakers being out of phase (only the 3.5s) could be there is no way to tell the speaker terminal polarity visually during assembly. So everyone seems to have different assemblies across all trims.
Also the stock speaker cones are a very fibrous paper. See demo:
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