Polarity identification of speakers

The pin polarity of speakers is relative, as long as the polarity of speakers used in the same room is consistent.
When more than one speaker is used, the polarity of the pins of each speaker needs to be distinguished for the following reasons: when two speakers are not connected in series or in parallel with the same polarity, the current flowing through the two speakers has different directions, one flows from the head of the voice coil and the other flows from the tail of the voice coil. In this way, when the cone of one speaker vibrates forward, the cone of the other speaker vibrates backward. The vibration phases of the cones of the two speakers are opposite, and part of the energy of the air vibration is offset. Therefore, when more than one speaker is used in the same room, the same polarity should be connected in series or in parallel so that the direction of vibration of the cones of each speaker is consistent.
The positive and negative polarities of the two leads are marked with "+" and "-" symbols on the wiring bracket on the back of some speakers, which can be directly identified.
The pin polarity of the speaker can be distinguished by audio-visual method. The two pins of the two speakers are connected in parallel arbitrarily and connected to the output end of the power amplifier. The electrical signal is fed to the two speakers, and the two speakers make sound at the same time.
Put the two speakers mouth to mouth and close to each other. If the sound gets smaller and smaller, it means that the two speakers are connected in parallel with reverse polarity, that is, the positive pole of one speaker is connected in parallel with the negative pole of the other speaker.
The principle of the above identification method is: when the two speakers are connected in parallel with reverse polarity, the paper cone of one speaker moves inward and the paper cone of the other speaker moves outward. At this time, the sound pressure between the two speakers decreases, so the sound is low. When the two speakers are close to each other, the sound pressure between the two speakers is smaller, so the sound is smaller.
The method of using the DC current range of the multimeter to identify the polarity of the speaker pin is: the multimeter is set to the minimum DC current range (microampere range), the two test rods are connected to the two pins of the speaker at will, and the paper cone is pushed inward gently and quickly with your fingers. At this time, the needle has a left or right deflection. When the needle deflects to the right (if it deflects to the left, reverse the red and black test rods once), the pin connected to the red test rod is the positive pole, and the pin connected to the black test rod is the negative pole. The same method and polarity regulations are used to detect other speakers, so that the pin polarity of each speaker is consistent.
The principle of this method to identify the polarity of the speaker pin is: when the paper cone is pressed, the voice coil moves, and the voice coil cuts the magnetic field generated by the permanent magnet, generating an induced electromotive force at both ends of the voice coil. Although this electromotive force is very small, the multimeter is in a very small current range, and the current generated by the electromotive force flows through the multimeter, causing the needle to deflect. Since the direction of needle deflection is related to whether the red and black test rods are connected to the head or tail of the voice coil, the polarity of the speaker pin can be determined.
The following two points should be noted when identifying the pin polarity of the speaker:
(1) When directly observing the lead frame on the back of the speaker, for speakers produced by the same manufacturer, its positive and negative pin polarity regulations are consistent; for speakers produced by different manufacturers, consistency cannot be guaranteed, and it is best to use other methods to identify them.
(2) When using a multimeter to identify the pin polarity of a tweeter, due to the number of turns of the tweeter's voice coil,