HI there, I am fairly new to sound, Have moved and am looking at helping with sound in my new church. It seems they need someone and I have a little knowledge, just enough to be dangerous!!!!

I am at the point that i now realize how much I do not know. Been reading in the study hall, other links in discussions and other sites.
Last Sunday someone else was running sound. I have not started yet, just asked me this week. There was a "empty rain barrel" or boomy sound from the song leaders mic. Cheap headset (not sure of brand) and infront of the main speakers, female singer.
I have sweepable mids on the board. I am thinking I can use these to remove the boominess? Any ideas what frequencies to start with?
Thanks for any help, sure i will be back as I start doing it.