(1) The speaker has two binding posts (two leads). When a single speaker is used, the two pins are not positive or negative. When multiple speakers are used at the same time, the two pins have polarity.
(2) The speaker has a paper cone, which is usually black in color and white.
(3) The shape of the speaker is round, square and elliptical.
(4) The back of the speaker cone is a magnet. When the external magnetic speaker uses a metal screwdriver to touch the magnet, it will feel the presence of magnetism; the internal magnetic speaker does not have this feeling, but there is a magnet inside the casing.
(5) The speaker is mounted on the machine panel or in the speaker.