What kind of power for outdoor installation?...

Discussion in 'Location Recording' started by BelafonteBill, Jan 22, 2008.

  1. I am new to pro audio, so please bear with me...

    I am looking into buying a simple PA system for an outdoor art installation project involving 100 people playing an alternative version of musical chairs in the desert at the Burning Man festival ( http://www.burningman.com ). I am looking for any advice on determining the needed specs on a system:
    * the area will be a couple hundred feet in diameter where the music needs to be decently audible
    * there will be no obstructions except people
    * the amount of participants / spectators could range from 100 to a few hundred
    * I will be running this off a small Honda generator ( found here: http://www.hondapowerequipment.com/ModelDetail.asp?ModelName=eu2000i )

    Any advice would be much appreciated. Thanks in advance.

    Bill Goodrich
  2. moonbaby

    moonbaby Mmmmmm Well-Known Member

    Welcome to RO, Bill!
    The generator you showed is only capable of producing 13.3 AMPS of constant juice. I use more current for Sunday morning sunrise services on the beach for hungover golfers who don't want to hear loud music at 7am! You have a problem, sir...
    Even a simple system- we'll take the Mackie self-powered box method, just for starters. This is NOT an endorsement, simply a comparison example. OK, a couple of small Mackie SRM450 powered speakers (@2.5 amps each), plus their smallest subwoofer -one of these-at 8 amps draw. There's your 13 amps. No safety room. No lighting. No mixer, music player, EQ, recorder, or even a gooseneck lamp. You're cooked. And you think that being outdoors is a "good thing"? Think again. Outdoor sound goes into "thin air". There is nothing to contain it, it goes everywhere, so you need a LOT more power to pull it off. Especially if there are performers who want to be "moved" to dance involved.
    You need to look at a LOT more generator. The (3) boxes I listed would be the very least for a small performance, and you better have the EU3000 for that tiny rig. And don't think that putting 2 generators to work will do the trick. That opens up a myriad of "ripple" and grounding issues.
    IMHO, I think that you should be getting a professional contractor to do this gig...
  3. Thanks for the response.

    I have heard from other forums that the generator is not beefy enough. I suppose I might have to rent a larger one.

    If that's the case, what wattage should I look for in a PA system?

    Does something like the following just look laughable?: http://www.guitarcenter.com/Phonic-Powerpod-740-Plus---SEM715-PA-System-630238-i1275606.gc
    ...or might it work?

    I am looking for something for a couple hundred people to hear decently well within a couple hundred foot radius. I know being outdoors really diffuses the sound dramatically, but it seems like with a small area I might be OK with something not-all-too powerful.


    Thanks much.

  4. moonbaby

    moonbaby Mmmmmm Well-Known Member

    "A couple of hundred foot radius" covering " a couple of hundred people" is laughable with less than several strategically-positioned stacks, subs, and wedges(the wedges are for the staging area). A big generator, torqued-up to provide maximum current will be needed to do this with the proper PA gear. This will certainly be too much ambient noise. I regularly do this with a 100-amp diesel generator and the ambient noise will kill the gig. It's a necessary evil in this case.
    Forget the Phonic junk. You need to set your priorities. I understand that you need to generate the desired sound pressure level (SPL) within a certain soundfield. The problem 'we' (I) have is that the soundfield is 'way too big for your budget/ideas. MAYBE you need to 'shrink' that concept down to a more manageable size. Is this a "performance" area, with dancers, and spectators "co-mingling" in 'harmony'? Then don't let it get bigger than , say, 100 feet in DIAMETER. Pound that area with a pair of
    "top boxes" and a subwoofer. Run the top-boxes off of 1 channel of the given power amp, the sub off the other channel. An electronic crossover will be needed to 'split' the signal from the 'sub' to the top-boxes. One of your "deal-breakers" is that when you want kickin' bass to move people, this requires a sub-woofer. No way around this. And a subwoofer EATS power-watts=current=amperes. Typically on a ratio of like 3:1. To keep the bass kickin'. AND to keep the top end clean. IF you can pull that area in, IF you use EFFICIENT speakers (i.e., speakers that convert the electrical energy to sound energy WELL), you MIGHT have a fighting chance to pull this off.. But, PLEASE don't say that you want this to cover 2/3 of a football field with a 2000-watt generator. IN YOUR DREAMS, BABY!!! DO you want to BUY the gear, rent it, what? Get back to me when you have a better idea as to your wants...and budget. And FORGET that EU2000...unless you're in a hurricane and want to keep the 'fridge running!
  5. MadMax

    MadMax Well-Known Member

    I'll pseudo second moonbaby's post... with some pseudo exceptions.

    I do a LOT of outdoors gigs as well.

    200 foot radius is 400 foot diameter. To cover a fairly open 400x400 area outdoors, you want to hit a good solid 96db w/o straining your boxes at roughly the 200 foot mark.

    IMHO you would be looking at 8-12 good typical tops per side and at LEAST 4 subs per side, but might be looking at 6-8 depending on how much gas in the ass you really want and how efficient the subs are.

    Here's the reason why... Outdoors, even a broad coverage box gets very directional. Some of them effectively go from a 60 degree coverage to less than 30 degrees. You need a good long trow, wide dispersion box that will be able to cover the area. Either that or you need to splay the boxes in an array.

    This just isn't a job for a little club PA. You need serious generators and serious PA gear. The stacks either need to be put on a deck, or you'll need to fly a smaller line array. Unless you're really a glutton for punishment, or you drop the size of coverage by at least half, it not 3/4...

    Hire a professional.
  6. eddyrock1

    eddyrock1 Guest

    BelafonteBill, I assume by the way you've described the venue using phrases like "simple PA system" and "hear decently well" that Max's response, while perfectly valid, may be a bit over the top. Can you give us a little more info?

    1) Is the coverage area a circle. (in-the-round).
    2) tracks only or instruments/vocals?
    3) what kinds of music?
    4) how long will the installation run?
    5) If not permanent, do you need to reuse or will you sell when done?
    6) What's the exposure to weather situation?
    7) what's the budget?
  7. BobRogers

    BobRogers Well-Known Member

    My guess is that moonbaby and max are designing to the wrong specs. Correct me if I'm wrong, but you are looking for a sort of old fashioned sports stadium PA rather than full audio spectrum music system. Think of the coach or band director barking orders through a megaphone from to tower rather than a stadium concert where the point is the quality of the music.

    I'm thinking that you want to mount 3-4 large "paging horns" on a pole, band limit the signal to 300-3K. Choose the spl you want at the edge of the circle and it will be a pretty straightforward calculation to figure the wattage you need. Choose your amps, add in a mixer, CD player, etc, and there are the specs for the generator.
  8. eddyrock1

    eddyrock1 Guest

    Yes Bob, I think you are correct based on the ginny he is looking at... *outdoors for a few hundred people* just is not enough information. Your proposal of horns on poles is kind-of the other end of the spectrum from multi-way line arrays. lol

    I was thinking the *passive two-way with a nice big amp* route. And if the ginny is for sound only, the power requirement is just not that huge imo.
  9. BobRogers

    BobRogers Well-Known Member

    Hey, if it was good enough for the Beatles at Che Stadium....

    (BTW, not a slip, I'm a Phillies fan.)
  10. moonbaby

    moonbaby Mmmmmm Well-Known Member

    This was stated that the system was to be used during a Burning Man Festival. I'm somewhat familiar with the goings-on there, but I did a bit of research as to the types of music that is played and supported at the event BEFORE I posted my replies. There is a wide range of musical genres played at Burning Man, but from what I could discern, a large degree is what could be labeled as "indy rock". And the dancing there is more akin to a moshpit than it is a twist contest. BTW, I won a silver dollar at a twist contest at the tender age of 6. How cool is that? :lol:

    The original statement that the performance area was " a couple of hundred feet in DIAMETER led me to the conclusion that this was indeed in a circle. And a circle that's, say, 200 feet in diameter, that would mean the radius is 100 feet, correct? So, digging into my too-many-cells-killed-by-high-SPLs-and-God-knows-what-else brain, I come up with an area of about 31,400 feet. And the coverage area later was stated that it would be 200 feet in radius, yielding a whopping 125,600 ft. But if there's somebody who knows math better than that here, let him speak out :lol:

    Seriously, that's a LOT of outside area to cover. Especially with the program material they're likely to be playing. Material that EATS subs for lunch! Anyway, my points to the original poster were that the generator he listed was pissin' in the wind, and that he should hire a pro. Peace.

    P.S. When the Beatles stopped performing live, one of the reasons cited was that the crowds were screaming so loud that nobody could hear them, and that they couldn't even hear themselves. No, Julia, they didn't have IEMs back then !
  11. BobRogers

    BobRogers Well-Known Member

    Moonbaby- You may well be right, but having done "The Children's Universe" at Floydfest for several years, I had a different reaction to "100 people playing an alternative version of musical chairs." My take was that this is not a venue for serious music, but a "fun and games" venue. One of the big things for the minor venues is not to compete with the "big ticket" venues. (I'm sure the hippies have a different, less capitalistic word for it, but I can never remember the lingo when I drinking good gin.) You are absolutely right if the goal is to cover that area with high fidelity music, but I'm guessing that is not the goal.
  12. MadMax

    MadMax Well-Known Member

    I too bopped up to the Burning Man site...

    The way I read and understand this is that Bill's actually doing this whole thing as part of his installation as an artist.

    Going on THAT assumption, either getting realistic about reducing the sonic requirements and scale it back to 50-75 people in a 50 foot diameter circle.


    If that's not what he's willing to do... then hire this out to professional production folks who will come do the job as it should be done.

    Because this is "an alternative version of musical chairs in the desert", that sound is going to die off bad... e.g. IF there won't be (assumption) a live band to assist with stage volume. This is evidently just tracks. W/O a live band, you will need at least twice the racks and stacks that you normally would.

    We're talking making a big record player to cover that +125,000 sq feet that moonbaby so astutely calculated. The coverage area per box and their individual directivity also should be figured in. Getting that much area covered and covered adequately is no small feat... especially when you have to throw decent audio 200 feet in a circle.
  13. moonbaby

    moonbaby Mmmmmm Well-Known Member

    After thinking about this last night, I have to say that you have a valid point regarding the fidelity the gig. Your recommendations reminded me of the first sound system that I owned: a Bogen Challenger 35-watt amp and a set of FOUR Atlas 'Banshee' PA horns. Oooooh, yeah, baby! I hope that my math was right, I would hope that you would've corrected me if not... :wink:
    We may never find out the "whole truth" because Bill sure as hell isn't saying anything now...we probably ran him off!
  14. BobRogers

    BobRogers Well-Known Member

    Burning tree may be more upscale, but if someone was putting on an "alternative musical chairs" installation at Floydfest. They'd be happy to ues your old PA. The two main stages were pretty much first class sound support all the way, there were four other stages (including ours) at the "outdoor community party" level (big for the Beer Garden and Dance Tent, small for the "Picken Porch" and the CU). Then there were a bunch of artist installations that had next to no budget and a very homemade vibe. I was just guessing that Bill was designing something like that, and that his sound requirement was that at the edge of the circle he could generate a sound sort of like my kindergarten teacher got when she dropped the needle on a 45rpm record back in 1962.

    On a more serious note, I would guess that what he really wants is around 70-80 dB SPL at the edge of the circle. How would you do the calculation if you were going to do the horns on a pole like I suggested? Is it a straight inverse square law calculation? (He asked - too lazy to go find his Yamaha Sound Reinforcement Manual.)

Share This Page