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Help with feedback

Discussion in 'Live Sound [BG]' started by pglaser01, Mar 25, 2014.


  1. pglaser01

    pglaser01

    Joined:
    Mar 19, 2013
    Location:
    St. Louis, MO
    Disclosures:
    If only I were that good....
    There was a topic I just saw on floor monitors that made me remember I was going to ask this. At our gig Saturday we brought the PA mains and mixer, our friends band played before us and he decided to bring powered wedges (Carvins, but not sure how old as they've been in his uncles studio for years) Anyway, levels for the mains sound alright, but as soon as the monitors go on...BAM! feedback city...I tried my best but couldn't get rid of the feedback even at very low levels, so we played without them. Their guitarist claims that at his practice space he uses them pointed right at him with no problems. Also I noticed he was using a Sennheiser e835, same as our vocalist. At our practice space her mic constantly has feedback when standing in front of the monitors.

    I'm no pro sound guy, but I'm the only one who has bothered to try and learn it. So how can I get rid of the problem. Is it a gain problem? Are these mics just really hot? Or are their frequencies I need to know about and try to adjust?

    Thanks guys!! I really want to learn this stuff!
     
  2. mrmills

    mrmills

    Joined:
    Jun 22, 2009
    Location:
    Kent, UK
    You need to identify which mic or mics are causing the feedback and which frequency or frequencies are the problem.

    Start by isolating the problem mic with the level sliders, once you know which mic is the problem, you can then start to look at what is the problem with it. Is the mic pointing at a loud sound source? are the sound reflections coming off walls at the mic? Make sure that loud sources are off axis to the mic, in zones that the microphone is less sensitive due to its pickup pattern.

    The pitch of the feedback will help you identify the problem frequency, a notch in the main EQ around that frequency can help. This really does depend on the stage, the room, the sound sources and the mics.

    Too much gain will cause feedback, always go for a bit more on the level and a bit less on the gain if the mic is not loud enough but you are starting to get the beginnings of feedback.

    Avoid lots of EQ on the PA/monitors as this adds gain and will make the setup sensitive to feedback in the frequency ranges with lots of boost. Try to get the EQ to level out at about the same volume going out as coming in, to minimise additional gain and keep the adjustments to small changes. Big cuts for a freqency might be needed if you are in a situation where the room/stage is very resonant.
     
  3. Zooberwerx

    Zooberwerx Gold Supporting Member

    Joined:
    Dec 21, 2002
    Location:
    Virginia Beach, VA
    I can't improve upon what mrmills has already pointed out. Do re-establish your gain structure...are you using your aux channels to feed the monitors? As a matter of practice, I routinely attenuate the 400-600 and 4K-6k sliders as this is historically where feedback arises.

    Riis
     
  4. pglaser01

    pglaser01

    Joined:
    Mar 19, 2013
    Location:
    St. Louis, MO
    Disclosures:
    If only I were that good....
    I do use the aux channels yes...good tip about the 400-600 and 4k sliders though...I will look at those
     
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  6. Frankjohnson

    Frankjohnson

    Joined:
    Dec 22, 2006
    Location:
    Dover Delaware
    maybe look also at mic/monitor orientation and placement. They can also just make a dicey situation worse.
     
  7. tbirdsp

    tbirdsp Supporting Member

    Joined:
    Sep 18, 2012
    Location:
    Omaha, NE
    Yeah - that high pitched scream you get is usually around 4 k...
     
  8. seamonkey

    seamonkey

    Joined:
    Aug 6, 2004
    You can get RTA apps that run on smart phones
    They will record to capture a time window also.
    It shows the peak of the feedback.

    You'd be better off spending your time getting IEM system going. No chance of feedback from monitoring.
     
  9. Zooberwerx

    Zooberwerx Gold Supporting Member

    Joined:
    Dec 21, 2002
    Location:
    Virginia Beach, VA
    No, that high-pitched scream is my wife when she finds out I used the good towels to dry the dog.

    Riis
     
  10. tbirdsp

    tbirdsp Supporting Member

    Joined:
    Sep 18, 2012
    Location:
    Omaha, NE
    :D

    What makes mine scream is when she finds out how much I spent on PA gear:eek:

    She's the one using the good towels for the dog...
     
  11. tedious1

    tedious1

    Joined:
    Feb 14, 2014
    And bottom line, even if it's the wife, she might still be at 4K...
    ...but she definitely won't have the slider!
     
  12. iceonaboy

    iceonaboy

    Joined:
    Jan 8, 2013
    :D
    :D
     

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