(1) The speaker has two terminals (two leads). When a single speaker is used, the two pins are not polarized. When multiple speakers are used at the same time, the two pins are polarized.
(2) The speaker has a paper cone, which is usually black and white.
(3) There are several types of speakers, including round, square and oval.
(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. There is no such feeling in the internal magnetic speaker, but there is a magnet inside the casing.
(5) The speaker is installed on the panel of the machine or in the speaker.