The Screaming Mic

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jokerswild

jokerswild

Chief Bottle Washer
Feb 11, 2007
18,776
1,288
Elkhart, IN
www.totalimpactdjs.com
No I'm not talking about some beligerant Scottsman... I'm talking about feedback problems with microphones....

This topic is for folks with the knowledge to pass on proper mic setup and gain structures to use with a variety of mic systems... I'll start with mine and allow folks to chime in with their ideas for setup and feedback control

My rig consists of:

1 Behringer DEQ-2496 Ultra Curve
2 AudioTech Freeway 202 Wireless Mics
1 Custom built PC using an EMU 1820m and dock for sound and mixing via Patchmix
1 Nady XA-900 Power Amp (or boat anchor as I refer to it)
2 Yamaha BR-15 Speakers
High quality cables used throughout the system
1 Furman power conditioner

Ok so that's my rig...

Within the patchmix software I currently have my mics virtually wired to my aux bus where I do all my effects handling... I think this may be where some of my issues with gain come from... but I don't want to taint any possible solutions with what I'm thinking until I can prove what I'm thinking is right or wrong...

I usually have my mic bases gain set to about 12 o'clock or less... and have never adjusted any setting within the mics themselves as far as sensitivity is concerned these mics are at factory default settings.

Thoughts?
 
Thanks, Rob. I moved this one to the Gear forum. Hope ya ain't mad at me. :)

I am not familiar with much of the equipment you work with so I'll welcome comments those who know.

In the meantime, here is what I can add: I used to curse mic feedback and noise in the old days. I was working with an inexpensive, unbalanced mic and unbalanced equipment.

All of that is gone. Every component is now balanced line, XLR and TRS. Our mics, wireless and wired are balanced line XLR. Shure SM58 with UT receiver. The wired mic is a Carvin CM 68.

We're currently running a 2/3 octave EQ, DBX compressor/limiter and active crossover. We typically bi-amp with a pair of dually 10" 2-ways on stands for tops and single 18" cab for lows. For the HS grad parties (and the Bachelor Auction shows ;)) we'll tri-amp and add a pair of dual 15" 2-ways for mids and run both 18" subs. We can push 6,000 watts RMS from three Class A/B Toroid amps.

Get this: a speaker can hold our wireless mic and stand right in front of the stacks with no feedback whatsoever. It gets out to the house. I am not kidding. We have done it many times. Brides thanking everyone for coming, folks doing toasts, ministers doing blessings etc. Give someone a mic and they'll walk all over the place. Mic noise is nonexistent with this system.

Here's where we eliminated the feedback: a compressor/limiter in the chain. Yeah, I know you all have heard it before but it's worth repeating. A C/L in your processing chain can eliminate mic ring. True, the EQ can (and should) be used to ring out mics but they can only do so much.

A C/L that's properly set will help to eliminate mic noise in a FOH system. Teaching mic users to use a mic properly will do even more to enhance your vocal mic tone. :)

Thoughts?
 
I've had many feedback problems too over the years. From karaoke singers and clients making announcements wandering out right in front of the speakers. I try to tell them stay in a certain area, but they forget. I have help this some with a couple of feedback killers.

1 rig has a dbx AFS-224 and another one has a Peavey Feedback Ferret. I always get the sound setup first and tell the people setting up that I am ringing out the feedback. Both of these unit work pretty good, but feedback can still sneak in if people do crazy stuff, including me. The killers react fast but you will still hear it before it gets filtered. Both units have a narrow filter but if you get too many filters locked in the quality will be degraded.

I also had a C/L unit in at one time but it died and I never replaced it.

Best advise, try to train the mic user to stay back (doesn't work with drunk karaoke singers) and keep speakers as high as possible off the ground.
 
Funny thing is with my last gig I was stationed off to the side but still very close to my left speaker and it was only slightly angled in towards the dance floor. But, from that point I had absolutely no feedback problems.... it was when I would venture out into the room that I had problems even when out to the center of the room more than 14' from either speaker.

I've since modified how I virtually wired.

Basically it works just like a hardware version of a standard mixer except it's all done on the PC

Using standard XLR inputs my mics are pluged into the Dock for the EMU-1820m sound card... the idividual gain controls are set to zero and on the mics reciever they are set to around 12 o'clock..

Within patchmix I have channel inserts for each and each insert is routed via Aux Bus 1... where I have a 4 Band EQ, Lite Reverb and Mono Delay effects placed... here is what I think is getting me in trouble... I can go from -142.0 to +12 on the input to the aux bus and from -142 to 0.0 or unity on the output back to the main mix.... I have been in the habit of running the input at +12

What I will try to do the next time I'm out live is to nix the aux bus and place the EQ and effects directly on the inserts and avoid the aux bus altogether... this may be the answer but until I can get this into a large live room I wont know for sure.

The DEQ-2496 does have a built in shark but I've never really sat down to figure out how it works and how to set it... the manual is very confusing... and it's as if I"M suppose to know what frequnces to center around in order to setup auto-feedback surpression...

What I need there is an expert in the use of it... and it's settings. Primarially all I use it for right now is the AEQ feature to get a flat eq response... works great btw.... I love it.
 
there was a previous post about this and Playback from the UK gave some awesome tips. You might search mic gain or mic blah blah blah
 
Jon Tuck said:
there was a previous post about this and Playback from the UK gave some awesome tips. You might search mic gain or mic blah blah blah
Click to expand...


Search turns up nadda.... says Mic is to short or to general to search with...


Stranger still is the gig before last required 4 mics so I had standard wired mics pluged into the Dock via XLR and my wireless in a line insert using TRS to TRS 1/4" again being fairly close to one speaker... only no feedback....

In both cases my speakers were from floor to bottom 5'6" off the floor... how do I know this? I raise them until I can stand under them and only feel my hair barely brush the bottoms....

The difference between the gigs other than hardware was the size of the room and the height not to mention building materials....

Environment is a major contributing factor... and it is impossible for me to compare the two... accurately... all I can speak for is the results.

In the first gig it was a huge pole barn with metal siding and little by way of insulation and a roof that was probably more than 16' high.

The second where the feedback was an issue was your standard garden variety banquet room with divider wall...
 
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