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Wireless Mic Questions

Discussion in 'Microphones' started by itsallkosher, Oct 9, 2009.

  1. itsallkosher

    itsallkosher Active Member

    Hey everyone. I'm running sound for a stage show (musical) and have some questions about wireless mics. If anyone could help me out some, I would greatly appreciate it!

    My first concern is feedback. When I start to get feedback, what is the first thing I should do? Cut the bass? I understand what feedback is, but what is the best way to remove feedback DURING a show performance?

    I'm a little confused with the wireless mic "sensitivity" setting and the wireless receiver "sensitivity" setting. For an example, let's say that a singer is peaking a lot. My best bet would be to turn the sensitivity from -20 to -30, correct? How exactly does that work? And there is also a sensitivity setting on the wireless receivers back in the booth. So if during a number one of the singers is peaking, is there anything I can do from the booth to make it better?

    If someone can answer some of the questions I would love it! I'm not an expert and I'm running the sound tonight for the show, so any knowledge would be wonderful! Thanks! :)
  2. Guitarfreak

    Guitarfreak Well-Known Member

    You know what feedback is and yet you don't know how to remedy it? I think this needs some clarifying. Feedback is caused by a temporary junction of input and output. The singer sings into X mic, the signal gets sent to XX gear, gets sent to XXX monitors so that the musicians and audience can hear it and if some of the signal from the monitors finds its way back into the mic it gets reprocessed and re-amplified again and again causing a cycle. This cycle is the source of feedback. So adjusting the bass is not what you'd need to do if this happens, I would lower the volume of the stage (not audience) monitors, or have the vocalist purposely stand far away from the stage monitors during the louder parts of the performance.

    Good luck with your production :D
  3. dvdhawk

    dvdhawk Well-Known Member

    [edit]Guitarfreak's advice would be appropriate for a band performance.

    I'm reading your post like this is more of a musical theater kind of stage-production using lapel mics. If I've misunderstood, I apologize. If you're trying to use lavalier mics AND run the lapel mics through loud stage monitors - your only hope is prayer - you're going to need a miracle to pull this together in the next few hours. [end edit]

    First of all you need to instruct the 'talent' to speak up as if they were not mic'ed. The more they project their voice to the back of the room (like stage-actors used to do), the less gain you will need to amplify them - virtually eliminating the possibility of feedback. Also, tell them that if they hear their mic starting to feedback - they should speak up and let you adjust the feedback out! The natural reaction would be to talk quieter, but that just makes it worse because you will be in the booth trying to turn them up so they can be heard. The first thing you should do if you hear feedback - turn the volume down, then try to find the offending frequency on the EQ and cut some of it as you ease the volume back up.

    If you get feedback you cut whatever range you think the feedback is in. It may be high, it may be low - or anywhere in between. In my experience, lows are less of an issue unless the speakers are hung overhead and your mics are picking up the bass lobe that radiates below the cabinets.

    If you're using lapel / lavalier mics, you will want to roll off most of the bass anyway. There's not much a lavalier can produce in the bass range that will be useful to you.

    If these are handheld vocal mics and you're getting feedback, you've got some speaker placement issues.

    If your receiver has a clipping indicator, you want to adjust the sensitivity on the wireless mic so that it's not overloading the mic first and foremost. Have the singer belt out a chorus or two while you watch the meter and adjust the sensitivity for maximum signal prior to peaking. If you don't have the mic onstage adjusted properly, there will be nothing you can do to un-distort it from the booth.

    The sensitivity on the back of most receivers is a different animal. It is to match the mic or line output of the receiver to your soundboard. Some also have a Squelch control, tricker stuff there. Usually the default settings are pretty good - so I wouldn't mess with the squelch unless all else fails. If you've got an actual volume control on the receiver run it about 80% as a good place to start, and make the broader adjustments with the gain on your soundboard.

    I hope that covers all your questions and makes sense to you. Good luck!
  4. itsallkosher

    itsallkosher Active Member

    Thanks for the reply. The feedback happens most when the bass player in the band or the keyboardist hits a LOW note, and I was told to lower the bass in this case. The speakers are overhead in this old theatre, so that might be the cause of some of it. The actors are using lavalier mics, and they are all very loud, so telling them to speak up won't really help.

    And what exactly is the squelch control? I've googled it, but I'm confused :/. Thanks again for the quick and helpful response!
  5. Codemonkey

    Codemonkey Well-Known Member

    Magical keyboard, eh? Appears out of nowhere. If there's an issue with all low notes, you need to cut the bass back. If it's a single note, you should be able to tune a 31-band EQ onto that note instead of using a shelving EQ on a mixer.

    Squelch, as far as I know, is to do with the receiver - turn it one way and you get more noise but greater distances before the signal drops. Turn it the other way and you get less noise but you lose the signal earlier. Most receivers will handle 100m easily unless you're in the dungeons of a stone castle.
  6. dvdhawk

    dvdhawk Well-Known Member

    Don't worry about the squelch, it's a function of the radio-technology that gates out weak signals and unless you're sure someone else has screwed it up - don't adjust it.

    If the feedback is really in the lower range, you will have to cut out some lows somewhere. In a lot of theaters the speakers are hung in a cluster just above the apron and angled down toward the seats. The horns (high-frequencies) are very directional and pointed out into the house. The bass frequencies fortunately / unfortunately are nearly omni-directional. So the result is a lobe of low-frequency energy the radiates down to the apron from above. Lavalier mics are often omni and if the actor stands in that lobe of bass for more than a second it has a change to regenerate. Sometimes this is a matter of change the blocking of the scene to avoid certain areas. Again, trimming the lows out of the lavs is a good thing to do just as a matter of practice. Dial in just enough to make the voice sound natural.

    Is the band on-stage playing toward the audience or in the pit? They will have to behave themselves volume-wise

    Does the bass start getting out of control just on certain notes? Re-positioning their amplifiers can make a world of difference. Your main EQ on the front-of-house system will help here.

    Does the bass start getting out of control just on any note below a certain key? Your main EQ on the front-of-house system and/or cutting bass off the signals at the mixer is the only thing that will help here.

    Waaaay off Broadway?
    Community Theater?
    College Production?
    High-School Musical? unlikely because you said they are very strong vocals
    Grade-School Musical? virtually impossible because you said they are very strong vocals

    I guess I really don't know what kind of stage-show this is, so I can only ask questions.

    Is tonight a tech-rehearsal or opening night?
  7. bent

    bent No Bad Vibes! Well-Known Member

    Decrease the distance from the source to the mic and increase (if applicable (or possible)) the distance from the mic to the monitor.
    This assumes of course that you are talking about a situation where you are performing your initial soundcheck prior to the talent arriving and you are pushing the mics as hot as possible to find out where the mic's begin to feedback and adjusting accordingly - if you're talking 'in show', and have decided for some reason to skip the initial soundcheck sans talent, then see the quote below concerning DURING show...

    It's an adjustable pad, i.e. it limits the voltage that the HH or BP TX amp receives from the capsule.

    And yes, lowering the sensitivity is correct, on the BP or HH - this step should have been done prior to the showtime cue being called.

    Any post above that mentions EQ'ing out the problematic freq's or riding the faders is correct. Mixing monitors keeps you on your toes. Use your ears (to identify the problem freq's), eyes (to see the cues that the talent is giving you), and hands (because that's what your fingers are attached to. Yes, that finger, the one hovering over the mid-sweep knob...).

    Me too - what make / model of RF are we talking about here?

    Solo the channel, make sure that you're not overloading your pre's or anything downstream - you're hard pressed to adjust the sensitivity of the HH or BP while the talent is out there doing their thing, should have compensated earlier during your initial soundcheck.

    The BEST way to avoid overloading your RF, whether Lav or HH, is to really get on the mic when you soundcheck. YOU as the engineer need to know how to project the piss out of your own voice as you check the mics that you will be in command of during the performance.

    Make sure you read my sig - Bob's quote is great, but so is the one about Gain Structure - learn it, know it, apply it...
    Make it your mantra...

    Last edited by bent on Sat Oct 10, 2009 1:30 am; edited some near infinte number of times in total (Mmm Hmmmm)

    The edited ticker below is a damn liar! 4 times my behind...
  8. bent

    bent No Bad Vibes! Well-Known Member

    As far as lavs are concerned, you MUST pick the appropriate lav for the situation.

    It's totally possible to run a show, with vocals louder than god, in which you have lavs in front of speakers that are blasting right onto the stage.

    Think about it.
    Polar Pattern.

    It comes right back to mic selection, mic placement, and gain structure...

    Don't believe for one second that it's the TYPE of mic that's giving you grief. More than likely it's the mic SELECTION that's doing it.

    (Should have put a headworn cardioid on the one with the squeaky, soft voice, eh?)

    (WTF do you mean "the producer doesn't want any mics visible to the guests?" ...the performer's wearing a fake beard, ungodly huge sorcerer's hat, and standing dead center of the R2's!!! Oh, he will wear the LAV on his forehead (nicely tucked up and out of sight, kinda pointing at the big, fake, bushy eyebrows - kinda pointing at the guests)? Are you f$%king kidding me?)
  9. itsallkosher

    itsallkosher Active Member

    Wow thanks for all the great tips everyone. I had almost no problems with the show except for a tiny bit of interference for only about 6 seconds! Thanks.
  10. JoeH

    JoeH Well-Known Member

    One other note: whenever you may get the chance (budget permitting, of course), move to headset/mini-boom mics. Everyone is making flesh-tone (bone, white, brown, etc.) plastic hardware now, and manufacturers like AT, Samson, DPA and Shure have wonderful over the ear headset mics that are all but invisible beyond 10-15 feet.

    The beauty here is that the mics stay right near the sound source (the mouths of the talent), and when their heads move, the mic moves with them. Gain stays consistent and overall MUCH higher before feedback. It's amazing no one hadn't thought of this years ago, but I guess the technology wasn't really there yet anyway, not with the quality of mics available now on the mini-booms they're offering.

    Some shows put them in the actors wigs or hats, while others pin them to their own hair/scalp, and use a little bit of surgical tape to keep the wires in place, down the back of their necks, etc. You can also use florist wire to keep the wires rigid and in place, esp if it's a fluid/mobile cast member.

    Good luck, whatever you do.
  11. bent

    bent No Bad Vibes! Well-Known Member


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