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PA Systems A forum for discussion of all parts of a sound reinforcement or DJ system: loudspeakers, mixers (desks) etc.

PA's run on a generator
PA's run on a generator
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Old 25th June 2012, 11:14 PM   #11
torclausen is offline torclausen
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Join Date: Mar 2012
Cool, I will definitely check the power coming out. Thanks.

Einric, I'll have to go without a line conditioner of that size, as thats 2/3rds of my budget. I'll first see how it sounds.

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Old 11th October 2012, 08:10 AM   #12
xsense is offline xsense  Sweden
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Join Date: Oct 2012
I registered just so I could comment on this post. Ive always been curious as why people always recommend so large generators to people who are on a budget. Granted that if budget and size was of no concern and you had a paying audience or tube amplifiers or other sensitive expensive equipment running your rules of thumb would make a lot of sense.

Contrary to common knowledge I have been running a sound system consisting of 2 single 18" bass bins and 12 inch tops + monitoring and other equipment of a single 1000 W inverter generator. There has been moments when dubstep has pushed this generator to its limits but those moments have been rare. A sound system almost never draws more than its rated power with common music material even though rated power usually means output power and not input power. I would say that the sound system more often than not draws less power from the generator than the rated output power from practical experience.

So id say go for it! Instead of buying an expensive power conditioner, buy a simple energy meter such as this: http://www.clasohlson.com/uk/Plug-In...er/Pr182027000 and use that to check voltage and power consumption. When you set up the sound system start with low volume and work your way up using the energy meters power indication as a reference. Stop raising the volume if the power consumption goes anywhere near 50% -70% of your generators rated power.
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Old 25th October 2012, 10:47 AM   #13
chrispenycate is offline chrispenycate  United Kingdom
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Join Date: Aug 2006
Location: W.Sussex
I discovered I had written a reply to this thread, and despite the fact it's probably too late for the person who was enquiring will still post it, in case anyone else might be interessed.

Low frequencies + small size = low efficiency.

Modern solution:- power's dirt cheap, throw more watts at it. Unfortunately, your generator system doesn't allow for this solution.

So, thinking old fashioned I see two classes of answer. The first, which I will call the Martin technique, is not to go for the ultra lows at all. Ignore the 35 Hz information completely, roll off everything below 60, (with an hpf before the power amp, so it's not wasting precious generator power heating up the coil of an unresponsive driver) and the equation shifts drastically. You can't use a hi-fi subwoofer for this, as they're designed for a flattish frequency response way down, not efficiency a bit higher, so this means building a cabinet.

The other solution bending (not breaking) the laws of physics is to make the cabinet 'look' bigger. Corner horns use the walls of a room to extend the cabinet, and its low frequency response; not necessarily in a linear fashion, but we're not hunting for the finest hifi response, anyway. I worked for a while with some very short bass horns which were delivered with some sheets of wood that clamped onto the front (flight case clips; got loose and rattly quite fast) enlarging the mouth to one and a half square metres; extra things to lose, and some additional set up time, but it does work, and without much transport or weight increase. The cabinets I'm talking about had 15" drivers, so wouldn't be optimum for your purposes anyway, even if I could remember the manufacturer (which I can't), but the principle holds.

Inflatable woofers? I never saw this used in practice, but if you load your driver into a large, spherical balloon, you get a near perfect omnidirectional wave from the entire surface. I don't know about efficiencies; the people I knew who were experimenting with it were more interested in coverage, but it seems possible that the increased surface area would work (thinking about the fact that we didn't get huge quantities of low frequencies from Rick's inflatable dinosaurs with their vacuum-cleaner air pumps, perhaps not).

Neutral detached? Yes, floating power, or centre tapped power is standard on construction sites, where safety committees have decided it reduces the risk of lethal voltages. We used to have an isolation transformer giving 55 – 0 – 55 volts. And there are a lot more of those little generators running power tools and lights than sound systems. Floating is actually a good deal easier to handle than centre tapped, especially if you're hiring the gear rather than buying outright.
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