Make sure that the panel jacks themselves are tightened. Check for fuses. There should not be any fuses for the woofer, but it is OK to have one for the horn or tweeters. Here are some simple steps to take. Just because an outlet has 3 holes, doesn t mean that they are all wired.
Proper grounding is important for two reasons.
If there is no earth ground , don t use that outlet. Plug all your PA electronics and amps into the same outlet. Lights draw an incredible amount of power, and dimmers create an enormous amount of electronic noise. If you hear a high-pitched buzzing like a mosquito, and if it changes as the lights are dimmed, then you are sharing a circuit with the lighting system. If you have to, run a long cord to the other end of the building just to get away from it.