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Live Elementary School Play Feedback Issue...


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I have been recruited by my kids' elementary school theatre director to help with their feedback problem...

To start with, I have suggested they only use two of their four speakers, since volume is not an issue.  Four speakers sending sound bouncing around the room seemed an obvious problem.  This is a relatively small are, and is a multi-purpose room with linoleum floors.  When it's full of people, the problem is less, of course, but they are having trouble rehearsing.  I have angled the speaker so they are not pointed directly at the back wall.

Their biggest problem is with their lavs.  I installed a delay box between the mixer output and the amp, but it doesn't seem to help all that much.  I am no expert in EQ to fix feedback, but since the mics are swapped around between kids with different voice, etc., I don't know that this will help.

Any suggestions.  Please ask for more info if you need it.

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Easiest way to eliminate the feedback problem is to move the speakers up in front of where the kids are by about 5 feet. If the microphones are behind the speakers then you cannot get feedback. Using only two speakers will also help.

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We did a test today, and with the teacher on a carpeted stage with curtains behind her.  The curtains in my picture are closed, blocking a small stage behind them.  We still had feedback on one lav turned up to a level that would allow us to hear a child.  Perhaps it was simply sound being bounced around the room.  All mics are behind the two speakers arranged like Alan's diagram.

Robert

The orchestra pictures are just so that you can see the room.  The 3rd grade play will be on the stage.  The orchestra uses no mics.

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I assume you are using lav mics rigged as you would for a job, on the kids chests.  With their small voices, the distance from their mouths to the mic, the hard room and the PA, you may be in a no-win situation esp with the mics being handed off between kids. You might want to rent a Sabine feedback controller, but it will be tough to set it up with different voices working all the time.  I have to ask--why is it that they feel they need a PA system?  All the plays my kids were in (last now finishing high school--both kids were serious "theatre kids" so lots of shows) didn't bother because they didn't have the resources to make it work.  You know how complex a Broadway type wireless set up is and that seems to be what is necessary to make it all work--no half measures.  If you decide you HAVE to do this w/ mics I'd go as much farther upscale as you can--enough mics that kids don't have to swap, hair mounts to get the mics closer to their mouths or rental E6 type earset mics, feedback controller and or enough EQ on hand to wring the room out.  In this case I firmly believe doing nothing is a LOT better than doing something inadequate.  If the instruments are drowning out the voices.....then they need to be conducted to play at a lower volume.  People's expectations for the technical aspects of shows like this are so high anymore, they are used to such high quality in movie and pro live sound that they will get upset at the first feedback burst or mic pop and will focus their full parental hate-rays on you.  I have been in this position more than once, and intend to never allow it to happen again.

 

Philip Perkins

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I talked to the theatre director today about not micing the kids, but I think they thought it would be better, and now they are invested in the concept.  I was in theatre as a kid too, and we never had mics.  We just had to learn to project as part of the "lesson" of theatre.

I think I am under qualified to use or explain the EQ of live mics to avoid feedback.  Not sure I can do anything.  I'll keep trying.

Thanks,

Robert

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There you go, I believe Philip mentioned it.  I also work with kids at my church and there's a HIGH chance of feeding back due to soft voices that the kids project.  Instead, I had to "ring" out the high frequencies because their voices were mainly chipmunk-type sounding and each kid had their own mics.  I remember that we didn't have enough mics for everyone so we had to switch mics back and forth between 2 or 3 kids, thus introducing EQ nightmares for myself and the audience.

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Along with the other suggestions here, if you have access to any kind of sweepable E.Q. (parametric, etc.), here is what I'd try:

Bring the gain of the overall volume up to where you are just below getting feedback.  Then, set the equalizer's Q for a narrow bandwidth.  Boost that freq's level up a few dB.  Slowly sweep the frequency until you start to feed back.  Be ready to bring the overall gain down quickly since we don't want to blow any drivers. 

The idea here is to locate the center of the bandwidth of the primary offensive room node.  Once you have located the center frequency, bring that frequency's gain down instead of up.  If you have more than one channel on the E.Q. you can do the same thing for the secondary offensive frequency.  The goal is to notch out the offensive feedback frequencies without adjusting so drastically that it damages the overall sound very much.  Of course, a bit of coloring if still preferable to feedback.

In many situations, more speakers (properly positioned) can work better than fewer since each speaker can be run at a lower volume and the reinforcement more evenly spread around the room.  This depends, of course, upon how the speakers are positioned.  With more speakers they can sometimes be located closer to the audience and you can benefit from the inverse square law.  With fewer speakers, they usually need to be positioned further from the audience so that the level is more even at all seating locations.

Next, tell the theater director that the sound reinforcement cannot totally compensate for lack of projection and counsel him to have the performers project more.  The lav's volume can then be set a bit lower and that will help also.

Like many things, the best solution is usually accomplished by applying a combination of several measures.  If each one helps a little, the combination of all of them can help a lot.

Good luck and let us know how it works out.

John B.

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If part of the problem is multiple mics open all the time then you might want to consider an auto mic mixer like a Shure FP410 or 810 that would allow only the mic in use to be open. It's a big help in reducing feedback.

Eric

OR, someone will have to actually "mix" the sound during the production.  The problem sounds like it could be too many mics open unnecessarily in a lively room.  Keep the mics behind the loudspeakers and close any mics that aren't being used and you will reduce opportunities for feedback.  You can ride a single mic right up to the edge of feedback and be OK, but open a second mic and things go haywire.  If you don't have enough mics for everyone, get a program (or script) and mark it with your cues ... and rehearse where each mic needs to go when a performer is done with it so you (the mixer?) will know when a mic can be cut.

As an example, if a kid does a performance behind the speakers, then walks to the front of the stage (downstage) for a bow, cut the mic.

(Former, and still occasional live sound mixer here.)

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A kid did the mix on the 5th grade play, and did a very good job I think.  A teacher is doing the 3rd grade play.  The problem occurs, however, with even one mic open.  I'll try the frequency sweep on the board and see if that helps.  Thanks for the explanation, John B.

Robert

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OK--no more unhelpful suggestions.  If you HAVE to do this w/ a PA, do you HAVE to use chest-mounted lavs?  Will any other micing scenario work?  (Handheld, headworn etc?)  This is kind of an "in for a nickel, in for a dollar" situation, and you should get some help  and the right tools to do the job.  Maybe some other parents are sound people, musicians etc and could assist you and kick in some gear.  I would also make it very clear to the teachers etc how complex an undertaking this is, and that it is outside your usual bailiwick and professional zone.

Philip Perkins

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They know this is not my realm of expertise, and I am only being solicited for some advice.  I am not running the sound or providing any gear, except lending them a delay box, which has proven pretty useless.  I will contribute on a couple of rehearsals next week.  Perhaps I can do some good then.  It's just frustrating not no be able to get even a "good enough" scenario.

Thanks again for your tips,

Robert

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They know this is not my realm of expertise, and I am only being solicited for some advice.  I am not running the sound or providing any gear, except lending them a delay box, which has proven pretty useless.  I will contribute on a couple of rehearsals next week.  Perhaps I can do some good then.  It's just frustrating not no be able to get even a "good enough" scenario.

Thanks again for your tips,

Robert

I hear that.  At every school event we ever went to that had a PA with a problem (most of them), my wife would nudge me and want to know why I didn't go help them.  I would answer, truthfully, that I didn't know how.  Asking a location sound recordist like me to step in for a complex PA job is a little like asking an amateur Piper Cub pilot who maybe just soloed to pilot an F18 on a particularly gnarly mission over Kandahar--same thing in general, but the devil is in the details.

Philip Perkins

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I have been doing PA since, well since the last millennium! ---actually all the way back to Jr. HS, which was a long time ago!

the technology has changed, the problems have not.

Anyway, I'm still doing some school plays (HS, Middle, and elementary!

"grade school" is the worst for a number of reasons, especially the little voices on the little actors, their short attention span, their only partially developed memorization and performing skills, their lack of projection....

it is not their fault that it is their fault!! (that is an attempt at wry humor!)

Usually the audience is on your side, as they are parents who all want to hear their little stars, but that raises the expectations, doesn't it??

absolutely correct: this is completely different from production sound!

OK, the delay is useless. that has nothing to do with almost anything involved here...any reduction in feedback would come at a price of increased reverb, and loss of ineligibility.

"If the microphones are behind the speakers then you cannot get feedback "

BUZZ,  wrong! but having the mic's behind the speakers helps a lot to reduce susceptibility to feedback...

"I assume all the lavs/mics are at least cardioid?

BUZZ  wrong; cardioid lavs won't help, will be much harder to work with, and will end up with poorer results

"and the same model?"

BUZZ  not much of a factor at all, actually; not important!

best weapon is a good feedback killer, my favorite this year (and last!) is the dbx AFS 220, but the better Sabine's (not the low end ones) are also very good.

Size does matter: in this sort of situation, more smaller speakers are better than less bigger ones, and the volume gets kept low,  you don't get "PA system" sound, but the speakers help the audience hear...

and better wireless mic's work better, as they have better or (even better!) no companding.

anything, and everything you can do to deaden the room will be important, as there will be less reverb, and that will result in less feedback.of the irchestra is between the actors and the audience, all the better,  put the speakers in front of the orchestra, and further in front of the actors.  Can the speakers (I like JBL control series for this) be flown across the front of the audience (and yes, I am referring to the relatively confined dimensions of these multi-purpose rooms. 

Here is something tricky: with the little kids, the teachers need to keep harping on speaking louder, clearer, slower, as well as facing the audience --we call it "cheating" but the little folks find it unnatural to not face the other person(s) on stage when they are talking to them.  ---and worst is when they face upstage and deliver their lines. the mixer person should work the rehearsals with speakers off and listening to headphones, that way the kids do not learn to depend on the SR, but the mixer will learn the cues.  during the last (dress) rehearsal, bring the speakers on.

also, if there are a lot of kids, and too few wireless mic's, then some carefully, well placed, area mic's can help, but they can also tend to be tricky... as stated, this is way different from production sound. the closest we may come to this is the traditional, multi-cam, live audience sitcom.

back to the feedback killers: there are fixed filters, and live filters, and a procedure for "ringing out" aroom or space.  the manual EQ is the same thing, only it requires skill, experience, patience, and is nowhere near a fast as the feedback killers can work, especially during the show. best to place these in the mixers insert point, so the exterminator can work with good levels, and then keep the amps turned down so that the PA is just there helping: that's sound reinforcement, and less is more!

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"I assume all the lavs/mics are at least cardioid?

BUZZ  wrong; cardioid lavs won't help, will be much harder to work with, and will end up with poorer results

What do you mean by "poorer"?

I have used Shure 183 (Omni) 184 (Supercardioid) and 185 (Cardioid) lavs, and I have always been able to get more volume before feedback using the 184 or 185.  The omni was all feedback!  I can see where the omni would work wonderfully with the right gear and experience (EQ, feedback killer, speaker placement) but in this case I would think the directional lav would make the most difference.

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while cardioid lav's are made with the idea of less feedback in PA situations, the cardioid lav's have a number of disadvantages: they suffer from proximity effect, and increased physical contact noise. unless placed in the hair, or on a boom (like the E6) they are going to really emphasize any "head turns".  (Even Countryman recommends the omni version over their cardioid version for most users!)  Broadcasters originally thought they would prefer them for their uses, but after they were developed (Countryman was among the first with their ISOmax series), and tried, they were quickly abandoned.  and of course they are more expensive and typically not as readily available to rent.

I think in the situation presented for this discussion they would not be any advantage, and I base this on experience.  I still have some old ISOmax's and Senn MKE-104 cardioid lav's buried in my office somewhere; they ended up being a PITA!!

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The biggest potential problem with the automatic feedback killers is accidently reseting them during a show. I was working as assistant on a high school musical a few years ago, the mixer reached over to pull down one particular freq and accidntly hit the reset button. The PA took off and the feedback killer took about 5 mins to finish ringing though. I leant from that one and only ever use a manual graphic eq on live shows now. Takes a bit more time, and on the plus side also trains your ears a bit with the frequency identification.

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to each their own....

I didn't say there is anything wrong with manually ringing out a system (but not during the show??  Also, the "training" referred to is certainly good experience, I know there are a lot of folks that resist technical assistance, like mixers who don't use limiters to protect their inputs or tracks from unexpected peaks, and yes, there are still a number of folks working that way!

but once again, lets consider the situation being discussed, OK??

"accidentally resetting" anything is a user error, and sure,those will happen, as will accidentally powering something off, not hitting record, or power kick-outs. Yeah, we all hate it when that happens.

the dbx AFS that I prefer is pretty automatic, and needs no adjustments during a show.  It comes back from power loss just as it was.  Resetting the filters requires rather deliberate steps, including holding one button for over 2 full seconds to reset the "live filters" and 5 seconds to reset the "fixed filters", which are normally set during the pre-show ring-out.

I have watched the AFS's lights show filters being set live before I heard any ringing, and I prefer it to my AMEX card for what I won't leave home without to do a PA gig!!

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Thanks for asking.  Remember, cheap lavs and 4 vocal mics and no fancy equipment were our only option.

On the first rehearsal day, where I was able to coach the 4 wired kids to speak up, it all went quite well.  The teacher operating the board was given a VERY basic tutorial about gain knob and fader, and limiting the number of open mics.  I sort of watched over his shoulder and reminded him to lower the other lavs when only one kid had a chunk of dialog.  We went with 4 speakers at a lower volume.  The drama coach INSISTED that the planted mics on the sides of the stage were left open to better hear the chorus, but it was totally unnecessary.  The group of kids were loud enough, and these were vocal mics not shotguns.  It only contributed to very poor sound (although not feedback) having these extra mics WIDE open.

The "dress" rehearsal for the other grades didn't go as well.  I parked myself in the audience, since I wouldn't make the actual performance day, and watched as a parent.  The wired kids were too quiet.  The teacher on the board kept turning up the gain, riding the level until feedback occurred.  They were still hard to hear and their voices were VERY thin from having too many mics open.  He also had the music too loud, even though he was sitting by a speaker, and I told him if he couldn't hear the kids over the music, neither could the parents.  The mics center stage were fine for the kids who were delivering into them.  The "outside" mics designed to fill the chorus were useless, but left up none the less, thinning out the lavs.  All in all, you more or less knew what was happening in the play, but if one of my kids had worked hard to remember a solo and had braved the stage to deliver it, I'd be pretty pissed to have it completely lost in the unnecessary over use of the PA system.

Not sure how the final performance went.  My son said it went well, but his group of 8 was more about the dance choreography supported by groups of singers, with the entire grade singing the chorus.  What upset me is that after the dress rehearsal I reminded the drama coach that the problem could only be solved by the lead kids (the ones on the 4 lavs) speaking up.  The drama coach said she was "tired of reminding the kids to speak up" and would no longer do it.  It surprises me that after all her hard work, that she would be content for the kids to not be heard, and for feedback to tarnish an otherwise wonderful elementary school play.

Robert

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" The drama coach said she was "tired of reminding the kids to speak up" and would no longer do it "

they are kids, they have short attention spans, and mostly:

that is her job!!

of course it is interesting that most of the time the teachers are constantly repeating: "please stop talking",  and when they are supposed to talk they have to keep repeating "speak up"...

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