Tell you the common sense of the voice coil of the speaker

2022 09/21

The speaker diaphragm voice coil is a basic electromagnet. If you read How Electromagnets Work, you know that an electromagnet is a coil, usually wrapped around a magnetic metal body, eg: iron. Electric current flows through the coil, creating a magnetic field around the coil that magnetizes the metal body around which the PA loudspeaker coil is wrapped. This region corresponds to the magnetic field around the permanent magnet: it has two polarities, one "North Pole" and the other "South Pole", and is capable of attracting ferrous objects. Unlike permanent magnets, it can change the polarity of the electromagnetic field. Change the direction of the current, and the north and south poles of the electromagnetic field change accordingly.

That's what a stereo signal does - it's constantly changing the direction of current flow. If you've ever built a stereo system, you'll understand that each speaker has two output wires, usually one black and the other red.

In effect, the power amplifier is constantly switching the electrical signal and fluctuates between positive and negative charges on the red wire. Because electrons always flow in the same direction between the positively and negatively charged particles, the current comes out of the speaker, flows in one direction, then turns and flows out the other. This alternating electrical energy causes the polarity of the electromagnetic field to change many times a second.