Use an AA dry battery and connect the two ends of the speaker to see if the speaker cone pops out or comes in.

To measure and judge the speaker phase, you can use the Ω×1 scale of a mechanical multimeter and touch the two test leads of the speaker. If the speaker cone is pushed forward, then the black test lead Because the positive connection of the mechanical multimeter battery is the black test lead), which is the positive terminal of the speaker, and the red test lead is the negative terminal.

Extended information:

In addition to using a phase detector, another simple method is to play a popular song and touch the cone of the speaker's woofer unit with your hands.

If the unit protrudes every time the bass drum sounds, it is in phase. If the unit corresponding to each bass drum sound is retracted, it is inverted. As for why pop music is used, it is because when the system is in phase, it is easiest to identify music with a lot of DC components.

Most bass drum recordings in pop music use the microphone placed on the outside of the drum. Every time the bass drum is struck, the drum head will protrude in the direction facing the listener and impact the microphone diaphragm, resulting in a signal with a positive DC component. Therefore, when it is finally restored, the speaker cone should vibrate in the same direction as the drum head. Protrude towards the audience.