It doesn't really matter if it moves in or out, as long as you're consistent about it...

And that's the trick. If you get it wrong for just ONE speaker, phase cancellation will make your bass sound like utter crap. It'll be like someone removed the woofers from your speakers.

The proper way to determine the speaker polarity in a factory install is to:

- Get a proper wiring harness for your car which will have the wires already labeled for you.

- If the color coding of the wires at the actual speaker locations is different from what's at the harness, then use a multimeter to test continuity between the harness and the speaker location.