Humming sound in speakers of a professional audio sys?

[Omar shuja]

Hi, TIM here!
I am having a slight technical problem with my sound sys... The set up is that i use FM wireless Microphone with And a normal table micropone(with cord) both together.. My speakers are placed about 30 feet away from the Microphones(Bothsides Left and right distance.Mic in middle) But i get a Humming sound in my speakers due 2 MIc catching the speaker's sound... so i cannot use full volume, rather to keep the noise low i ave to run the system at low volume.. which makes the sound too low for audience to hear? What should be the distance between spaekers & Mic??
Thanks

[Tomi Engdahl]

What type of microphones do you use and how they are placed related to speakers?

The best tools to fight against feedback from speakers to microphone is to use a goo directional microphone (cardoid or hyper-cardoid) and place the microphone/speakers so that the speakers are at microphone pickup pattern minimum.