(1) the speaker has two terminal (two) lead, when single speaker use only two pins both positive and negative polarity, more than a speaker at the same time when using two pins have polarity.
(2) the speakers have a paper bowl, its color is usually black and white.
(3) the speaker shapes such as round, square and oval a few broad categories.
(4) is the magnet on the back of loudspeaker paper cone, outer magnetic loudspeaker with a metal with a screwdriver to touch the magnet when they feel the existence of the magnetic; Magnetic loudspeaker inside there is no this kind of feeling, but there is magnet inside the shell.
(5) the speakers on the machine panel or speakers.