Dynamic range compression will help control the amplitude modulation you're experiencing, but it will not correct for bad microphone technique, nor will it solve any feedback issues - and in this application, there is no side chaining involved.

An EQ can help with feedback by allowing you to back down the frequencies that are feeding back so you can bump up the rest of the signal before it starts feeding back.

Microphone selection and positioning also come into play. A hyper or super cardioid microphone will generally allow more gain before feedback, but requires the talent to stay on axis more than with a cardioid.

There are also "feedback destroyer" devices you can put in the signal change. These are simply automated notch filters doing the same thing the EQ can do, but automatically and with a narrower notch in the frequency band.

I second what Karl has to say. Much of what you describe comes down to good engineering practices by experienced personnel.

Dynamics processing such as limiting/compression can be added to live PA reinforced microphones only after the feedback issues have been dealt with first and proper levels carefully adjusted. This coupled with proper speaker placement with ample distance from the microphones. Not microphones whose speakers are close by and parallel with the microphones with wide dispersion horns, as in a smaller venue such as your church. That is a recipe for feedback.

It may also be worth noting that many people install 1/3rd octave graphic equalizer's into their PA systems. Most people don't even know how to use them correctly. I frequently see people have them adjusted with nice "smooth curves". That's what the program equalizers do on the audio board! That scenario might be fine if you are trying to "voice" a speaker system, that feature separate drivers and not an integrated complete speaker. That nice curve it is certainly NOT FOR FEEDBACK SUPPRESSION.

Unless you have a really excellent ear and can identify what frequency the feedback is occurring at, you would need a properly calibrated microphone with an integrated spectrum analyzer. That devise will give you an instant visual indication of what frequency you need to pull out on the 1/3 octave graphic equalizer. The automatic frequency feedback reducers automatically identify the feedback frequency/frequencies and automatically reduce those particular frequencies. Many people expect too much out of those units as they are only there to be able to deliver a little more sound before feedback not ultimate loudness without feedback. Plus many people don't understand that to use those automatic devices, one must allow the feedback to start SCREAMING, until the device properly identifies the frequency and then starts to nul it out. All too often, I'll see amateur audio guys with those automatic devices turn up the microphones until they start to feedback and then they immediately back down the level of the microphones. That defeats the purpose of the device. They don't understand the directions in the manual.

Add water and stir.
Ms. Remy Ann David

Dealing with amateur performers can be highly frustrating, no matter how talented they are. Are you using monitor speakers on stage? Many times, a singer may back off the mic as a psychological response to hearing themself. This is a result of someone who is not used to hearing their own voice playing back to them. It can throw off their timing, their sense of pitch, and may cause them to "shy away from" the mic. If you are using monitors, turn that vocalist DOWN in that mix. This will force him/her to work the mic closer to their mouth to hear themselves. I have dealt with lots of church-based performers for years and getting them to properly "work the mic" is a challenge, but definitely "do-able". And worth your time and efforts. If you need printed documentation to help school these people, try going to the ProSoundWeb (Google that as 1 word) site and select "church sound". That section has had some VERY good tips on
proper mic techniques for the stage. Remember: garbage in, garbage out,
good sound starts at the performer.

Yes i do use stage monitors. I should try lowering the volume of the vocalist and see if that helps. but i think i really have explain a few things to her. Second, i'm getting feedback issues cause there are so many reflective surfaces in the room that we use.And the speaker placement is a major issue because of the room's wierd design it has emergency exits in all the places that are not really helpful to me :cry: , and i cant block them. with regard to using a feedback destroyer. i need to get more cause when i use that on the main mix, it interferes with the electric guitar. Or how about sending all the vocals to another mixer and adding the feedback destroyer to the main outs of that one, and back into the Foh. i dont know how that would work. any feedback guys? Thanks for the help i really appreaciate it. 8-)

My experience is that good feedback destroyers can help with minor problems, but not major ones. They can't substitute for good speaker placement, good mic technique, and appropriate stage volume. Cheap ones are not worth the trouble.

Get your singer a foam windscreen and tell her that she should see her lipstick on the front of it by the end of the show. Tell her to imagine that the mic is a cardboard tube and she is trying to sing into it. While the band is playing talk to her without amplification 18 inches from her ear and one inch from her ear - on and off the axis of her ear.

Good luck.

Good advice on the windscreen trick. I have found that some women find them a bit intimidating, especially the red ones...wierd.
There are so many variables in any scenario, and we really don't have enough information to go by. I am curious, but why do you find the emergency exits a problem? What shape is the room-long or wide?
I own and use a couple of Sabine feedback exterminators...they are great, but you DO have to get the basics right first. What mixer are you using? If it has subgroups, you should be able to assign your vocals to one of those, and patch the controller into that sub's insert loop. Most all mixers with subgroups have that capacity these days. You might even try
patching the unit into a single mic channel. That's really the best way to use many of those-on a single mic. And what mic are you using? Are the speakers on poles? How are they aimed in relationship to the staging and the audience?

i'm using a allen and heath mixer. i dont have major feedback back issue's anymore i figured that one out. why do i find the emercency exits a problem? Cause the room is a wierd polygon shape with exits on all four conors and 2 doors on opposing side's of the left and right walls! I dont get why they did that. When u see how small that room is u might wonder why they did that as well. anyways my original post was out of curiousty. I was just confused how they got the sound to sound same at diferent distances from the mic. Dynamic compression makes sense( the problem was that i was just over thinking to get to the solution).I dont need much to get good sound. i was just trying to be all fancy lmao. i really apreciate the help guys! good looking out folks 8-) what would i do without all of you!