We label our terminals so that when a positive DC voltage is applied to the speaker's positive terminal, the cone will push out away from the magnet. Generally speaking, the positive terminal is usually on the left when the speaker is facing up. On our neodymium models, this is opposite. The positive terminal is marked in red on the right when the speaker is facing up.
It is also easy to identify the polarity of a speaker with a 1.5V battery by connecting the negative lead of the battery to one of the speaker terminals and the positive lead of the battery to the other speaker terminal and observing which way the speaker cone travels. If it moves out, then the positive speaker terminal is the one connected to the positive battery lead. If the cone moves in, the positive battery lead is connected to the speaker's negative terminal.