Microphone feedback

Any information on the following annoyannce would be appreciated.

I am having trouble with microphone feedback

It is an SM58 going through a beringer mixer. I have tried position of mic and speakers, gain, getting the singer to only stay in the half inch zone, shark feedback destroyer, but nothing seems to fix the problem. I am not overloading the mixer, we are always under 0db on main. The AKG radio mic doesn't have any probs.

Any sound gurus out there with practical knowledge, ideas or suggestions?

the mic is broken in my opinion, if you have REALLY tried everything that seems the most likely theory...you can try other mics and see how they behave, but I'm almost sure that the 58 has a problem.

(hey thank you for making me feel a "sound guru"....which indeed i'm not )

No, the feedback creeps in, usually when the singer moves back from the mic. It is a backing singer mic, so not in use all the time. I have tried placing the speakers behind, adjacent to and in front. The feedback destroyer picks up the feedback and kills it, but it can only allocate 10 frequency levels and the feedback seems to occur on more than these freqs. This means once it has allocated the 10 it goes back and steals the ones it has already allocated, leaving the original frequency open for feedback again. This of course controls the whole level of the system. I cannot get it to the levels I would like to be playing at. These levels are not excessive (small club, pub level). Maybe it is just an unresolveable problem that occurs with the combination of the sm58, behringer mixer and peavey PA & JBL speakers. The whole system only has an output of 300W, so i am not dealing with massive power output.

Edited by cobb