Help Sound System Gurus

[psychofunk]

Just like the title says, I need help from you sound system gurus. My church sound system is getting a rediculous amount of feedback from the cordless mics. I can barely turn the volume up on the mic mixer and mic input on the sound board. Can you guys please help me. I guess firstoff I need some background help. WTH does feedback come from? Is the source the board? The mics? The mixer? Can it be anyone and all of them? Sorry for what may be stupid question but I know nothing about sound systems and thanks in advance for your patience and help.

 

[psychofunk]

Holy crap this thing ended up in the abyss of Anandtech, it was so far back I had to do a search to find it. Anyways bump, can anyone help me please?

 

[yhelothar]

Try not to have the speakers directed at the mic :disgust:

 

[glen]

YGPM

 

[cucumber]

Like the first reply sais, pointing a mic at the fronts of speakers will cause this. The ideal place for using a mic is behind the speakers. This way it's impossible to point the mic and the speaker drivers. This of course isn't always possible or convinient. If cordless mics are used try walking all around the church to see where the feedback occurs. You'll likely find that it will happen in some areas and not in others.

If moving either the speakers or the person using the mic is not easy or possible, you could use the EQ on the mixer to tame it somewhat (lowering the higher frequencies can help, but it usually won't get rid of all feedback though.)

You might also look into getting something like this:

http://www.musiciansfriend.com...etail/base_pid/182463/

This will detect what frequencies are causing the feedback and it will EQ them to get rid of feedback.

The best fix is to not point the mic at the speakers, but if that isn't possible (speakers may by installed and not easily moved...etc...) then getting something like what's shown above should help.

 

[psychofunk]

Glen....right back at cha

cucumber....What exactly do you mean by don't point the mic at the speakers? Is that a literal statement? Does the mics transmitter pick up on some freq that causes the problem? Or is it a matter of the sound emiting from the speaks entering the mic itself and being spit back out of the system?

Sorry for the newb questions and thanks to you all for any and all replys, I really appreciate you taking the time.

Jerry

 

[KingNothing]

Originally posted by: psychofunk
Glen....right back at cha

cucumber....What exactly do you mean by don't point the mic at the speakers? Is that a literal statement? Does the mics transmitter pick up on some freq that causes the problem? Or is it a matter of the sound emiting from the speaks entering the mic itself and being spit back out of the system?

Sorry for the newb questions and thanks to you all for any and all replys, I really appreciate you taking the time.

Jerry

Yes, it's literal. If the mic pics up the sound from the speakers that it's transmitting through the system, the slight delay will cause feedback. For instance, at my church we have two speakers above the stage in the center, and two stacks on the left and right of the stage. I never put the wireless mics in the side speakers because it causes feedback if the guy wearing the mic gets close to them. At the same time, if I turn the sensitivity up too high and he gets right underneath and in front of the center speakers, feedback again.

By the way, when you say wireless mics, do you mean the handheld or the clip-on kind? The clip-ons will always be sensitive to feedback. The solution is to try to keep the guy wearing the mic behind the speakers, and to EQ out the frequency of the feedback. Typically feedback will only occur at one frequency so you just have to be patient and find it. In our system the frequency is around 1200Hz, I think? It's about a third of the way up on the high-mid dial.

 

[CombatChuk]

Is the GAIN on the mic set too high up?

 

[cucumber]

Yeah, it was a literal statement. Also, you don't realy have to be directly pointing the mic right at the speakers either. If the mic is pointed in the general direction of a speakers drivers (the moving parts [cones or horns...etc..] that put out the sound) it could cause feedback.

The mic picks up noise from the speakers. This is the cause of feedback. When the mic pics up any noise coming from the speakers it gets amplified and sent right back through the speakers. So it creates a loop of sound that being picked up by the mic, amplified, and sent out the speakers over and over again. This is why it gets louder the longer it lasts.

What kind of mics and speakers are being used? If your mics are more directional (they pick up noise only from what's directly in front of them) it could help reduce feedback. If the mics are more omni directional (they pick up noise from all directions) it would be worse for feedback.

Are the mics handheld or small clip on types? The handhelds tend to be more directional and the clipons tend to be more omni directional.

Any ways, despite what you're using, a feedback destroyer should do the trick for you.

 

[psychofunk]

KingofNothing (great name btw)....I was actually speaking with one of your kind fellow members and he was able to determine that part of my problem is also the fact that we have big plaster walls that are baren so the sound is bouning around everywhere. I will see about making some changes there to reduce some of that resson...reson...resnonanannce....yeah that stuff (I know I'm a dork but I have fun with it).

Another big thing your guys are bringing up is that speaker placement is a problem so I will try and make some adjustments there. We have some other speakers that I may be able to use that may help in widing my placement options.

As for the types of mics we have both. The pastor like to have the lapel/clip on type (of which there is an extra for visiting pastors), singers/praise team/music get corded mics (so of course no problems there) and announcements/welcome address/etc. use a cordless handheld which is less of a problem than the lapel/clip on. I will do some tinkering and see what I can find out.

Combat....the gains are set at 3 of 10 as any higher and we get a loud sharp feedback that gives you that seashell hearing for a minute or two.

cucumber....I will check into the mics but I do believe that they are omni directional because they have that little fluffy thing on em. Maybe I will pic up a uni directional from frys (the one for computers) and see if I can modify it for out needs (I was hoping for another reason to break out the dremel).

And that shark thing, I assume that is the feedback destroyer you are referring to? We have a sound store guy who is really cool with us but i don't know if he carries that brand, are there some other options that I could check out. I mention this only because I know he will allow us to use it and see if it works and if is does not then he will allow us to bring it back. Or is the shark guaranteed, I know you cannot guarantee but is it guaranteed to work??

Thanks again fellas, you kick ass (hey, relax, I'm christian, not perfect). I was already writing this thread off. I honestly cannot believe how much posting goes on here, it is simply amazing. Anand has to be the biggest forum on the net, I mean like a hundred pages worth of posts before lunch. If what they say about reading helping lessen chances of alzheimers then you certainly won't get it here.

Jerry

 

[cucumber]

Well, as for the shark, there are other brands and models out there that do similar things. I just put this one because it's one of the cheapest (still very effective though). You could order it from musiciansfriend.com (owned by guitar center). They have a 45 day return policy. If you don't like it, send it back. You'd have to pay shipping though. The sound store guy would likely help you out too. See what he offers. He may also have some advice for the audio setup to solve your problems.