Football Stadium Graduation

[dwardMICS]

My school graduates it's students in our football stadium. Last year, I brought out a separate PA system because we had some issues with the stadium system. Now that it's fixed, I do have a question for all of you who are WAY smarter than me regarding this stuff.

First here's a picture of the stadium:

Second, a run down of the ceremony: the speakers are attached to the score keepers box. The ceremony takes place at the 50 yard line. The speakers will be speaking facing the stands. We are using a single wireless mic at the podium. The stands will be filled by family and parents.

So my question: Is this going to cause the worst feedback in the world? Last year, I had so much bounce from the bleachers that I getting all kinds of crazy feedback. But I am doubly worried that it will be worse because the speakers are going to be shooting down from the press box to the center of the field, right in view of the mic.

Is there a baffle or something that I can get to try to shield the mic? Or should I be prepared to get hammered for the horrific feedback?

 

[MNicolai]

Primary sources of feedback in this application would be poor EQ or over-gaining the mic to compensate for presenters who are too far away from the mic capsules. Educating your presenters in advance of how to properly speak into a microphone goes a long way. If they are standing a couple feet back from the mic and you have to gain it up to the heavens so the presenters can be heard, then there's really nothing you can do to avoid feedback.

The more critical issue you will have is delay. If the presenters are down on the track or on the field, they will have 50-100ms of delay from the time they speak to the time they hear themselves back through the PA. This comes across to them as an echo and can make it very difficult to keep track of where they are in their speech or song. I highly recommend dropping a monitor wedge near the presenter's mic that will cut through the sound of the press box loudspeakers and minimize the presenters' perception of an echo.

 

[dwardMICS]

Primary sources of feedback in this application would be poor EQ or over-gaining the mic to compensate for presenters who are too far away from the mic capsules. Educating your presenters in advance of how to properly speak into a microphone goes a long way. If they are standing a couple feet back from the mic and you have to gain it up to the heavens so the presenters can be heard, then there's really nothing you can do to avoid feedback.

The more critical issue you will have is delay. If the presenters are down on the track or on the field, they will have 50-100ms of delay from the time they speak to the time they hear themselves back through the PA. This comes across to them as an echo and can make it very difficult to keep track of where they are in their speech or song. I highly recommend dropping a monitor wedge near the presenter's mic that will cut through the sound of the press box loudspeakers and minimize the presenters' perception of an echo.

Thank you for the input. So assuming the my speakers use the microphone properly (which is sadly a stretch with high school students), the feedback should be somewhat avoidable? Sadly, it's a VERY basic system without an EQ or an extra audio out. I'll climb around today to see if I can even daisy chain a monitor off one of the mains.

 

[MNicolai]

Depends on how well the system is tuned, or in some cases if the system is tuned at all. Not uncommon for electrical contractors with a low-voltage division to try and do these as "hang and bang" installs, and then not tune the system because they don't know how to. If the installer is a reputable AV contractor, then it's generally safe to say they at least spent some effort making it sound good.

FWIW, in a well-tuned system you should be able to stand in the direct flame of a speaker about 15' away at normal show level and speak into a handheld mic without any feedback at all.

You don't want to daisy chain a monitor off of your mains. Firstly, your amps many not be sized for that. Secondly, you don't want to send them same EQ/gain to your wedge that you send to your mains. You want a separate AUX send off a mix console, or a discrete additional output from your DSP.

Photos of your mixer/rack/amps/DSP/etc would be helpful.

Worst case, if you have a 2nd wireless receiver in the same frequency band, tune it to the same frequency as your handheld and drop it with a portable mixer and a little powered speaker next to your presenter's lectern. So long as you aren't playing back music from the press box for the national anthem or backing tracks for a special musical piece, there's no reason you have to run the wedge through the installed system.

 

[TheaterEd]

Can you add a small board between the wireless mic and the system to add your own eq and aux out? That's what I do in our gym for graduation.

 

[TimMc]

I'll mention that adding a monitor loudspeaker at the lectern will not be a panacea solution as it will require a whole lot of output to overcome the stadium PA.

EQ for the monitor will be essential or it will be another source of feedback whilst trying to achieve the SPL needed.

 

[FMEng]

With a significant delay echo heard by the persons at the microphone it could be very difficult for them to speak coherently. A monitor speaker might help, but it might not. As Mike wisely pointed out, it needs to be driven by a separate amp so that you have precise control over its level, and so you don't effectively short out what might be a 70 Volt distributed line on the main speakers.

I suggest setting up a test as soon as possible to find out whether this arrangement is survivable. If it's not, you may need to get on a sound for hire company's schedule pronto. This is exactly why so many of those companies are very busy right now.

 

[StradivariusBone]

My colleagues have to deal with this dilemma (I am lucky and our stadium is a bit too small for graduation and our school does it at the local roadhouse). Most of them get the school to buy specific equipment for graduation and then maintain and run it for the ceremony. I think most of them set up speakers on the stage and then the kids sit on the field. It might be worth having a conversation with your admin to start investing in a purpose-designed setup for this event. Initial cost yes, but then you no longer are at the mercy of the rental companies for support.

 

[JD]

Can't over-emphasize how big a problem the delay can be. Having experienced life on both sides of the microphone, it can stop someone dead in their tracks mid sentence. Monitors fight this a bit, but the speaker still hears their voice twice. The only way around this is to have the main speakers located at the stage where the microphone is at. My vote- don't use the stadium system.

 

[spenserh]

I do A2 work in a stadium from time to time, PA consists of a bunch of clusters hung at the top of the stands circling the entire stadium, all point to field level so while each stand sounds fine because it can't hear the sound coming from the other side, the sound on the field is complete mush. We often drop a set of monitors for the singing of the National Anthem, it certainly doesn't eliminate the problem but it does help.

If the speakers can all have a chance to hear their voice through the PA prior to showtime, that will make a larger difference than the monitor, it will at least lessen the chance that they are going to go all "deer-in-headlights".

 

[FMEng]

The problem with buying equipment for graduation is twofold. Covering a large area outdoors takes a fair amount of above average equipment, not a pair of Fenders on sale at the local music store. Some districts have staff that can handle the setup and operation skillfully, while others have to rely on student techs. I know there are some very professional student techs (especially those here on CB), but banking on having someone who excels with audio every year isn't a good idea. Hiring a pro and developing a long term relationship is more likely to be successful year after year.

 

[StradivariusBone]

banking on having someone who excels with audio every year isn't a good idea.

Totally agree. In my (and I suspect also in OP's) situation, the school does have someone who could handle that task. If this is dumped on the IT guy or media specialist that is the de facto audio engineer for the school, then contracting a company would be the best solution. The upshot of buying a grad system though is you end up with more gear that sits around for 11 months out of the year and no one minds if it's used for other projects.

 

[Ben Stiegler]

Going back to basics ... human ears are *directional*. Sound coming from behind the pinna is attentuated, with highs (speech freqs) more affected than lows. What size crowd are you expecting? Will grads sit int he stands, too, or on the field?

I would approach this by renting / stealing powered speakers or passive speakers and an amp rack that would allow placing the speakers or horns *on the field*, facing the audience. This solves so many problems
- no slapback from the opposite side bleachers
- direct to reflected ratio is much better
- you can run lower gain
- the delay issue for the human presenters is not such an issue.

If you are primarily reinforcing speech (vs. playing bombastic recorded music), you can also get away with much less audio power (no need for stacks of subwoofers, etc).

Side trip down memory lane - I remember attending my brother's law school graduation outdoors at Tulane some decades ago, and the darn PA was ringing for 2 hrs during the ceremony - really distracting. I got up to go lend a hand, and my parents (who hadn't really grasped that their son was a competent, self-responsible adult yet) stopped me. Bless their hearts, they still think of me as the 10 year old who would disappear behind the curtain and make friends with the techies, while they worried I was bothering someone.

Bottom line - graduations are emotional moments for families, and I hope you can make it sound good enough that everyone can both hear and understand what is being said!

Catch me offline [email protected] if I can give you more help on sizing, geometry, required audio power, etc.

 

[taneglaus]

I didn't notice anyone suggest using a hyper-Cardoid or super-Cardoid microphone. This will help somewhat with the feedback issue. Be sure the back if mic is pointing straight or slightly down. If you look at the mic's polo pattern you'll see the back lobe.

But, EQ & stage monitors are going to be your best friend.

 

[n1ist]

I was at my daughter's graduation Sunday. Graduates were on the field, guests in the stands on either side. They had a ground-mounted line array on either side of the stage, facing the graduates. Nobody in the stands could hear much of anything...
/mike

 

[StradivariusBone]

I was at my daughter's graduation Sunday. Graduates were on the field, guests in the stands on either side. They had a ground-mounted line array on either side of the stage, facing the graduates. Nobody in the stands could hear much of anything...
/mike

From my own personal experience running audio for a BBQ fest at our stadium, ground stacked over grass tends to attenuate a lot. I ran a pair of 3-way cabinets with an amp driving around 700-1000 watts per channel IIRC. We weren't trying to hit the stands, just the majority of the field but it was hard to hear much past the 50 yard line and we were set up in the endzone. The next year I took some powered speakers I had (that were considerably less powerful) and put them on sticks and you could hear it in the parking lot. I'm guessing the 6-8' elevation made a big difference.

This is for a fundraiser our school does (BBQ, games and a car show) and they usually have a couple student and faculty bands perform, so it's not critical that we blow the walls down. We just use gear we've got and experiment. However if you go the speakers on the field route, my experience says getting them elevated, even just a bit, will help immensely. I'm sure the more knowledgeable of the booth can contribute the math (or maths) behind it, but I have heard this mentioned before.

 

[KBToys82]

Our school has outdoor graduation in the stands and the setup has always bothered me. The stands aren't very wide, probably between 25 - 25 and I'm not sure what speakers are pole mounted, but they outside the stands with 2 of the larger speakers facing away from the crowd and the 2 smaller speakers facing the crowd/field. We have the ability to turn the big speakers off, which helps a lot because they instantly cause delayed bounce back from the school and you can't concentrate on what you are saying when you hear yourself a second later.

A few years ago I petitioned the school to get an install of a field level input that goes directly into the amp. So last year I tested out having a Mackie mixer with my microphones be able to plug directly into the new input, and from the Mackie mixer, I also went out to my Yamaha StagePas 400i mixer/speakers which were positioned on poles about 5-10 feet in front of the stands on the track. These helped immensely with the sound, and much clearer than what is mounted for the stadium. Also helped to some degree with what the speakers/graduates heard on the field as well, even though it wasn't facing them.

Next I'm trying to get the school to look into a portable setup that will have it's own power amp, speakers and mixers for a better setup.

 

[JD]

Going down memory lane, I did sound for my own high-school graduation. It was on the football field. Used a pair of Altec A7s up on frames, loaded with 421-8H LF drivers, and 291-16C's on 311 horns crossed at 1khz, bi-amped using a vacuum tube Dynaco 70 for the horns, and a pair of MO-200 200 watt vacuum tube amps driving the lows. Gately mixer and (some things don't change!) Shure SM-57 mics. Everything worked and was crystal clear... up until some idiot tripped on the extension cord cutting power and leaving me scrambling, still in cap and gown to get things up and running!