The more drive units the harder it will be for the designer to make it sound good. So be wary of inexpensive designs with multiple drivers. Speakers sold on specifications tend to be aimed at the less experienced buyers. Hifi Corner have superb demonstration facilities and there is no substitute for listening yourself. Terminals at the back of the speaker are marked 'plus' or 'positive' and 'minus' or 'negative' .
Amplifiers also have at the back 'positive' and 'negative' terminals.
They may be colour coded. If one of the terminals is misconnected then the speaker is said to be out of phase. Basically when one of the drive units is moving out on one speaker, it will move in on another. The net effect is that bass is lost as the speakers are working against each other. Stereo becomes diffuse and it is difficult if not impossible to localize sounds in the middle of the speakers.