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View From the Balcony |
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Generators Mark Nichols August 2005 How can summer be almost over? At least here in Georgia, where school starts early August, I'm seeing "back to school-back to church" signs. No wonder time seems to be flying by. What does that have to do with church media? Lots. Over the next few weeks, many of you will be asked to provide audio support for outdoor events such as back to school rallies and Fall Festivals. Very few ministries have a portable system just setting around waiting to do outdoor gigs. Most of us have to scavenge from several systems to get enough parts to piece together a make shift system that might be loud enough for the parking lot. We will spend the next two Views on "Parking Lot Tech" First thing you need is power. Nothing works until it is plugged in. Audio and lighting, especially lighting, is power hungry. Four 500W lights take up an entire 20 amp circuit. So, two lighting trees need two breakers, and audio amplifiers need another 20 amp breaker. We don't want to be anti-social, but we cannot share our power with the popcorn popper! Stringing three extension cords out a window and across a parking lot is not good, either. For the record, 16 AWG extension cords from the discount or dollar store don't fly. The amount of current audio and lighting draws demands 14 or even 12 AWG grounded power cables. The solution? Take the money you would have spent on good extension cords and rent a generator. You don’t need a huge trailer drawn diesel three- phase model, unless you are doing a pro level concert. (read Kent's article on "The World's Largest Portable PA System" We used a 36kW generator) Many Home Depots have rental generators, as do party rental places and tool rental houses. On the positive side, a generator gives plenty of power to run both audio and lighting, and the power is pretty stable, although I would still use a surge protected power strip at the end of each extension cord. To be fair and balanced, I must admit that generators are loud and heavy. The heavy part is easy-that is why God invented teenage boys. As to the loud, when Cornerstone Media carries our small generator to a show, we use a product called Versi-panel to knock down the noise. (www.mitylite.com) But you can just as easily buy one roll or bundle of insulation and staple it to a 4X8 plywood held up with two legs. Total cost less than twenty bucks. With generators, size does count. A very small generator, 3,000 Watts or less, will run a lighting tree or two but will have trouble running a large PA with subwoofers. Somewhere near 6,000W will run lights and sound with some headroom left over. The math for generator size is easy—count up the wattage of every light and add it together. Generators are listed in Watts, rent more generator than you have lights. Audio is only a little harder. Forget the power rating of the speakers-all that counts is the amplifiers. A stereo amp that produces 500W per channel at 4 ohms would draw 8.3 amps just before clipping, but in real numbers, it is closer to ten. Two power amps and a front of house rack on 20 amps should be okay. I know I have been tossing around numbers a lot in this article, so here is where the numbers come from. A(very) little math and (even less) history. A Watt, named after Henry Watt, is one Ampere (the measure of current) at one Volt. The formula looks like this: W=I*V. In English this time: Watts equals Amps times Volts. A 20 Amp circuit at 120 Volts produces 2400 Watts. Most generators will not produce exactly 120 Volts, anywhere from 108 to 121 is okay, but I highly recommend surge protectors when dealing with smaller than trailer mounted generators. This article is longer than I intended, so I'll leave you with two more quick thoughts. First, never let your generator run out of fuel. Remember what a lawn mower sounds like as it runs out of gas? That sputtering is death to anything plugged in to the generator as the voltage swings all over the place! Finally, treat connecting a generator as a life and death matter-it is-yours! If you do not know exactly where to connect a wire, don't guess-get help. I don't say that to scare you, well, yes I guess I did. I want to scare you into being careful. Remember our motto at A View from the Balcony: "don't be a high tech redneck." Happy Mixing! Mark |
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