Not the flying half-chicken fart move!

Actually if you unplug from the amp you would be getting no voltage/reading

Yes, you could check for the voltage at the speaker end with the wires off the speaker and a volt meter, this would give you the correct polarity, if a negative voltage shows up on the meter you know you are connecting the meter backwards.

Though your idea would still allow you to check for continuity with a multimeter....

Use all safety precautions! Unplug, discharge static, wear hearing and eye protection, don't operate heavy machinery, beware of erections lasting longer than four hours...yadda, yadda, yadda...

ain't no juice without no circuit...

I love Google Search also....

You could disconnect amp & speaker. Then connect a 9 Volt battery at one end and check the other with a DC voltmeter to identify each wire.

I think it's just a phase he's going through.

Another simple method to check for polarity is to use a AA battery. Disconnect the speaker wires from the amp, and connect the 1.5V AA battery to the 2 leads. If the woofer on the center speaker moves outward, the lead that was on the positive of the battery is the positive. If the woofer moves inward, the lead that was on the positive of the battery is the negative. Using a AA battery ensure the voltage going to the speaker is low enough to not cause any damage.