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khachai44

Help line array system at a school

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My wife works at an awesome summer camp for kids every year. They write and stage their own play-slash-musical. It's quoite a spectacle, though it's consistantly plagued by being completely inaudible to anyone beyond the first row.
The kids aren't great at projecting. 
Being a composer & sound designer (aka, a guy who knows stuff about audio) I've been tasked with remedying this problem. I'm not a live sound person, so I'm looking for some guidence. I'm mostly looking for help with type of mics and their placement to best amplify the (often mumbed) speaking voices of kids ages 6-12 on a small school gymnasium stage. http://amthanhthudo.com/loa-line-array
Do I go with shotgun mics? Do I go with some other kind of mics? How many? A left-center-right configuration? Do I suspend them or floor/stage mount them? Looking to keep it in the $200 rental range. I own a Senn MKH416, so I could throw that into the mix. I'll probably just run everythink into a small Mackie with PA speakers. If you, the professional live-sound person, where tasked with making your child's school play audible, what would you do? Many thanks for any suggestions.

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It might help if you posted this in the general section or 2 channel or some other, it might get more replies ? This section is about sub's, but you will probably get some answers anyway, but maby more in other sections, no problem but I would like to see you get some answers. :emotion-21: 

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The only person I know who is actively working with mic's and live recording is @Mallette, Dave Mallette.  I bet he has some invaluable insights he could share.

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Take a look at PZM mikes.  They've been used successfully for this purpose.  Mounted on clear plex, they can be flown unobtrusively over the stage to provide an overlapping and even coverage.  Their 180 degree coverage is an asset in such applications in limiting return from the audience and off axis areas as well as minimizing feedback.  Done properly and fed to high quality (Klipsch pro would be perfect, but Heresy would likely work as well) speakers it would sound like they were just talking louder.  It's been a number of years since I purchased the four for SoundCube, but at that time they were running 150-250 on Ebay. 

 

Dave

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On 5/15/2017 at 10:13 PM, khachai44 said:

My wife works at an awesome summer camp for kids every year...it's consistently plagued by being completely inaudible to anyone beyond the first row. The kids aren't great at projecting. 


...I've been tasked with remedying this problem. I'm not a live sound person, so I'm looking for some guidance. I'm mostly looking for help with type of mics and their placement to best amplify the (often mumbled) speaking voices of kids ages 6-12 on a small school gymnasium stage.
 

Do I go with shotgun mics? Do I go with some other kind of mics? How many? A left-center-right configuration? Do I suspend them or floor/stage mount them? Looking to keep it in the $200 rental range...Many thanks for any suggestions.

So the microphone issue isn't a trivial one, in my experience.  Reinforcement is a different animal than recording, in my non-professional engineering experience and as a musician.  Usually drawing a picture of the stage in elevation and in profile to understand where the source of the major first reflection sounds are coming from is a worthwhile experience.

 

I've got a couple of books that I use.  I recommend reading up a bit because the exact geometries of the stage, mike placement, and reflections/absorption coefficients vs. frequency are usually part of finding the solution to your problem without dong a bunch of trial-and-error stuff.  I personally use John Eargle's microphone book (chapter 18) for this sort of thing, but there are much better resources out there, I'm sure.

 

EDIT: another source from Shure on the subject--https://web.archive.org/web/20110303041801/http://www.shure.com/idc/groups/public/documents/webcontent/us_pro_mics_for_music_sound_ea.pdf

 

As far as loudspeaker arrays--I've learned that line arrays are usually a lot more trouble than they're worth in terms of speech intelligibility, and that if you can avoid them it usually works in your favor.  See: http://www.danleysoundlabs.com/danley/wp-content/uploads/2012/01/line-array-paper.pdf

 

Chris

 

 

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Post a picture from audience center of the stage with a wide angle.  That will help.  These need not be complicated or expensive to achieve an improvement. 

 

Dave

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For $200 you're simply not going to accomplish your goals. Floor mic'ing is not a viable solution to this problem. I could explain why, but my experience tells me you're going to try it anyway.

 

So to get the most out of floor mic'ing, the first step is to get the right polar pattern. Don't use highly directional mics (no hyper-cardoid). Use a standard small diaphragm condenser microphone with a cardoid pickup pattern. Position the mics in such a way that the rejection null of the microphone is pointed towards the source of your feedback (the speakers). And if you have control over the speaker position, then work hard to minimize the amount of sound from the speaker that ends up on the stage.

 

Your goal here is to maximize the "gain before feedback". This is a boring physical reality that can be quite readily calculated. There are ton of articles on the subject, but it all amounts to minimizing how much sound from the speaker ends up in the microphone. The reality is you will be limited by the gain before feedback.

 

The other thing that limits the gain before feedback is the number of open channels. You can buy yourself another 2 to 4 dB by riding the faders and only having one mic turned up all the way at a time. The unused mics don't need to be attenuated by more than 10dB for this to work. There are automixers that do this for you (Shure SCM810 or SCM820), and some digital consoles have this functionality built-in. (Yamaha TF and QL series). I'm a little biased towards the SCM820 since that was one of my projects at Shure.

 

========================

 

That said, if you really want to solve this problem as dictated by the laws of physics, then you need to individually mic each kid with a lapel or headset mic. Even then you're going to be limited by the gain before feedback - especially if they're not projecting. In the professional world, this is solved by using several wireless microphones. Ya, I work for a wireless mic company, but that is not biasing my recommendation here. You might be able to rent enough wireless gear for $500 to $1000 for this musical depending on how many channels you need. Figure $50 to $100 per mic per day.

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On 5/16/2017 at 7:51 AM, Mallette said:

Their 180 degree coverage is an asset

It's more of a liability to be honest. You don't get a rejection pattern with a PZM - this reduces your GBF.

 

On 5/16/2017 at 7:51 AM, Mallette said:

Klipsch pro would be perfect, but Heresy would likely work as well

The Heresy absolutely would not work. That small cabinet with a single 12" driver has no control over the polar response....that translates to lots of bleed back onto the stage, which also reduces GBF. Most of the Klipsch pro line suffers from the same problem.

 

You need to get into the bigger horns before the pattern control starts to get controlled adequately. There is some Klipsch pro that accomplishes this.

 

Line arrays control the vertical polars extremely well - but they often don't control the horizontal very well. Whether or not that matters depends on a lot of factors. The amount of horizontal control varies quite a bit too.

 

The thing about these devices is that they are tools. Anyone getting on a philosophical pillar about which method works best doesn't understand the intricacies of the tools. Just as a carpenter may have multiple saws and hammers, so does the sound engineer. The factors for sound quality in the live sound world are totally different than any audiophile pursuits that might be discussed here.

 

If you're looking for a good pro audio resource, then check out this website:

http://www.prosoundweb.com/

 

They have forums too.

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I forgot to mention one thing....with any microphone solution, you're going to need to EQ the feedback frequencies. These frequencies are unique frequencies that wrap around the speaker or microphone due to their construction. There are often 3 to 6 of these frequencies that exist - while all the others tend to be well behaved. Be careful though because these frequencies slide around with position. EQ'ing out these frequencies is basically flattening the off-axis response of the system, which lets you turn the microphone channel up higher. There are feedback reducers that do this automatically for you, but they don't work better than an educated operator. All you need is a high Q parametric EQ.

 

Don't get crazy with this though - notch the first few frequencies and then don't try to add more. You'll hear when it's enough because the feedback will move from one tone to a series of multiple tones.

 

This is why hyper-cardoid mics are bad....they have big spikes in the off-axis response. The goal is to have smooth rejection patterns. For both the speaker and the mic.

 

The thing is, the good microphones and speakers that do this aren't cheap.

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31 minutes ago, DrWho said:

It's more of a liability to be honest. You don't get a rejection pattern with a PZM - this reduces your GBF.

I have no idea what a GBF is, and, much as I love you, have found it pointless to disagree as you are an engineer and I am just a schmuck who has spent half a century chasing great sound.  Use of the PZM in these applications isn't something I invented.  And the 180 degree pattern has been proven to my satisfaction in my SoundCube surround experiments and I've used it on podiums as well where its pickup and pattern allowed much greater amplification before feedback than any other type.  Hoping to move to serious testing of that system with real engineers soon. 

Not sure what your issue is in stating that "Heresy just wouldn't work."  The one PWK placed in my home church here in Texarkana is still in use and still, to quote the original ad, "...most people thought the minister was just talking louder." 

Dave

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GBF = Gain Before Feedback.

 

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5 hours ago, Mallette said:

I have no idea what a GBF is, and, much as I love you, have found it pointless to disagree as you are an engineer and I am just a schmuck who has spent half a century chasing great sound.  Use of the PZM in these applications isn't something I invented.  And the 180 degree pattern has been proven to my satisfaction in my SoundCube surround experiments and I've used it on podiums as well where its pickup and pattern allowed much greater amplification before feedback than any other type.  Hoping to move to serious testing of that system with real engineers soon. 

Not sure what your issue is in stating that "Heresy just wouldn't work."  The one PWK placed in my home church here in Texarkana is still in use and still, to quote the original ad, "...most people thought the minister was just talking louder." 

Dave

Heresys set up properly. will do just fine...they were used for stage monitors for years...and the HIP models have been used on or off stands for years in reinforcement/PA applications.  It isn't like you need lots of low bass response for reinforcing the voices of children, anyway!  Therefor the tweeter and the midrange horns of Heresys with the upper bass from the woofers would probably do the trick!

 

Here is another thought....since it is a summer camp environment, if the stage itself was set-up in a natural bowl-type location, OR was backed by high ground immediately behind it (preferably in a semi-circle)...or BOTH, the environment would readily enhance the acoustics of what was being said/sung on that stage...if it worked for the Ancient Greeks and Romans, it will still work today.  Ever heard of UDINE, in Northeastern Italy??...not very far from Trieste??  Huge Roman stadium there in the mountains...back in the day (1973-1976) three-day-weekend concerts were the norm in the summer months, even though there was no train going to the town...artists and bands choppered-in and concert-goers took buses in from the closest train station...not enough housing/hotels for all the people but plenty of camping space!  I went there every summer when I wasn't elsewhere being an infantry paratrooper and got to really love that place!  Pretty much everybody who was anybody played there back in those days...Pink Floyd, Alice Cooper, Ten Years After, Blue Oyster Cult...the list goes on and on!

 

Let nature show you how to project, if at all possible!

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2 hours ago, DrWho said:

GBF = Gain Before Feedback.

Copy that...but don't get why you think a 180 degree pickup isn't virtually ideal.  As I said, my experiments with PZM's which were based on others work indicate they deliver the best GBF of any other mike at a given distance.  That wasn't specifically why I chose them for SoundCube, as feedback was irrelevant.  But the fact they have a very flat pickup within their natural pattern of 180 degrees was.  Four on one meter plex provides a nearly perfect 360 degree pickup with distinct and clean separation. 

 

Dave

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While not a professional I have done live sound for 30+ years and learned mostly the hard way. Currently I am mixing sound for my church that has children sing and perform plays and skits, mostly around holidays. We have the same issue hearing the children especially the younger ones. The only solution I have found that works is to mic each of them. I do not work for Shure but I do use their wireless SLX mic's for this purpose - cheap mics are feedback producers. Also some eq'ing is needed but since I am using identical mics the parametrics are almost the same for each. *** One must remind the parents to have children dress in clothing that the wireless mic can be attached too, including the transmitter pack.

 

I very much agree with @DrWho as he is explaining my hard lessons with the laws of physics. Lastly I do "ride the mutes" and for that reason also use mute groups as well - anything to raise GBF. :)

 

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I am backing out of this one as it is turning into one of those internal debates that don't do anything to help the OP.  My own suggestions from experience were flat contradicted by some, and supported by others.  I would suggest the OP pick a person they deem qualified and deal with them directly by phone, email, or PM.  Otherwise, this important work may wind up in analysis paralysis.

 

I certainly hope that he figures something out of all this that is useful. 

 

Dave

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If it were me I would go with this Davida Rochman lady.

 

http://blog.shure.com/how-to-mic-a-choir/

 

http://www.shure.eu/support_download/educational_content/microphones-basics/choir

 

Do you know her @DrWho?  Your crew seems to be pretty experienced at this.

 

Why couldn't you mike for choir without elevation (flat stage) and use one wireless mike for any solos?

 

He wants an improvement, not perfection, and he has a $200 budget.  There is no way to get any improvement?  

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15 minutes ago, dwilawyer said:

He wants an improvement, not perfection, and he has a $200 budget.  There is no way to get any improvement?

 

For $200 the choir mic technique may be the only choice and I have done that with mic's on stands. Unfortunately the issue still remains of the children not projecting well and with the mic's several feet away the problem will still exist. I would agree that this technique will provide some improvement especially for the children that do speak up.

 

P.S. This technique can pick up a lot of unwanted noise as well such as paper shuffling and sounds made by the children moving around.

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Here we go!

 

Sound reinforcement in one of my hobbies, too! 

 

For $200 (add some of your own money?), you'll have to do what ever you can.  Shotgun mics will have to track the speaker, but since you have one, try it! 

 

The 3 mic choir configuration works, with the right mics.  And I'm intrigued by Dave's suggestion of PZMs on a sheet of plexiglass.  If the loudspeakers are are sufficiently forward of the mics and you can EQ out the room modes, you won't be chasing a child with a shotgun.  A Countryman mic on every child would be excellent, but $$$$$. 

 

I would hang the mics overhead for visual appeal, if I could. 

 

Since this is your first attempt and on a budget, gather what you can and give it a whirl.  There is no ideal, try something.  It won't be worse than nothing. 

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