the polarity marking (i'm surprised nobody else mentioned this) means that if the + terminal is positive (i.e. on the positive half of the waveform), the cone moves out. this is most important with woofers or multi driver cabinets, since the cancellation effect you would get using two stereo speakers out of phase would be most noticeable for bass, or in the case of a speaker cabinet with two woofers, two mids, and two or more tweeters. also with woofers (and especially subwoofers), when you are playing music that has a pronounced kick-drum, the effect of having the woofers moving IN when the kick drum is hit, makes the music sound like it's missing something. you hear the kick drum, but it doesn't sound right. there are people who take the whole "absolute phase" thing and blow it completely out of proportion, but it isn't really that important except at low frequencies.