How do I check polarity on loudspeaker?
The reason for keeping the polarity of speakers the same in an audio system is so that you don't end up with a phase difference between channels if different channels are connected reversed. If you have a single speaker the signal is AC so it doesn't really matter which way around it is connected. Assuming you do have multiple speakers so the polarity matters:


Often the negative is a smaller pin but regardless if the speakers are identical the polarity won't matter as long as all are connected consistently.
Otherwise you can check the polarity by attaching a battery but especially for a small speaker like that (probably only 0.25W) I'd recommend a 1.5 V battery and even then don't it leave it connected for very long because speakers don't like DC applied for long. Probably even safer for a speaker that small would be to put a 100 ohm or so resistor in series which should still give you enough deflection to see.


As already mentioned the convention for polarity is that a positive voltage on the positive speaker pin will cause the cone to move outwards.