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Generator for small PA system

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Generator for small PA system

Postby Sam Spoons » Mon Jul 22, 2013 2:55 pm

I have an outdoor gig next month and it's off grid power. I have hired generators but for this one I had bought my own (hopefully it'll earn the outlay back in saved hire charges).

I've already done all the calcs and come up with a figure based on either the 1/8th rating of my speakers (QSC K12s and Yamaha DXR10s), a measured, full load current consumption (My 18watt guitar combo and the bass players Ashdown Superfly) or an educated guess (EV SbA750 sub and Alto TS110A). What I'd like to know is are the published 1/8th power figures realistiv or wildly underrated. Most of the gigs I will use it on are small acoustic events so I won't be using backline and when I do I will scale the PA to suit the available power.

The Genny is a Kipor IG2000 (a frighteningly accurate Honda EU20i clone) rated at 1.6KVA and 7A continuous and 2KVA and 8.7A max I know it'll run the acoustic rig of 2 x K12's and 1 or 2 x DXR10s easily but It'd be nice to think I could run the full rig if required.

Rig is as follows :-
2 x QSC K12 active tops 1000 watts RMS rated 1/8th power consumption 1.13 Amps at 230 VDC
2 x Yamaha DXR10 active monitor 700 watts RMS rated 1/8th power consumption 90 watts so 0.4A
1 x EV SbA750 Active Sub 750 watts RMS say 0.5A (I will measure this when I get time)
1 x Alto TS110A active monitor 300 watts RMS say 0.25 (and this one)
Mackie DL 1608 mixer say .5A
18 watt valve guitar amp. 0.34 A measured
1 x Ashdown Superfly Bass Head 1.4A measured

That adds up to 6A. Anybody got any thoughts?

Just a final point, there are issues with Petrol and Health & Safety at some venues, the genny is primarily for my own use but if I start to get those kind of gigs I'll consider the LPG option.
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Re: Generator for small PA system

Postby tacitus » Mon Jul 22, 2013 3:59 pm

Taking a rough guess and assuming you don't power everything up at the same time or run flat out on heavy metal, you'll be fine. And assuming your figures are round about accurate. Beyond that you'll want a proper expert opinion rather than mine.
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Re: Generator for small PA system

Postby Sam Spoons » Mon Jul 22, 2013 8:05 pm

Thanks Tacticus. I have a couple of numbers to confirm or test (the Yamaha tech support guy didn't have much idea really, beyond what I'd already figured). I may not even get to run the full rig from it this year, mostly it's acoustic stuff for which it'll be fine. I will try the plug in meter next time I run the full rig (into the mains, I'll have to get someone to watch it when we're playing a loud bit :blush: ). It's the 1/8th power thing which I'm concerned about, is it a realistic figure in the real world (and no, it's not heavy metal).
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Re: Generator for small PA system

Postby tacitus » Mon Jul 22, 2013 8:21 pm

I can certainly vouch for the average current draw being well under the maximum on the plate, as I've done PA for bands and orchestras where the peaks are few and far between. I just don't know how that compares to 1/8th power as I've never been in that situation or run my PA with a meter on to measure it minute by minute. From my own experience I'd deduce that you need to run very loud and hard to get anywhere near the full rating of the equipment - like a DJ for example.

As often as not I have sufficient power to match the actual ratings on my equipment's specs, so if it's actually running anywhere near 1/8th power I've got heaps in reserve. When I quote for work my estimating spreadsheet automatically compiles a power rating for the gear I'm planning to use. It's printed on the quote and I expect that to be available when I turn up.
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Re: Generator for small PA system

Postby Sam Spoons » Mon Jul 22, 2013 8:58 pm

Before I started to look into this that's what I would have done but, for my personal rig (which does get hired out but not every weekend) I couldn't consider the size or expense (which goes up exponentially with power output) of a 6KVA genny (which is what I'd arrive at by that method), if that's what is required I'll either hire, use a smaller rig or refuse the gig. Hopefully the 2KVA Kipor should do the job for everything I will do. If it won't run the full rig with sub and bass amp, miked kick etc then I'll live without on these gigs or hire in a bigger genny.

I did a few gigs with a guy who runs a solar powered mobile stage (http://www.mobilesolarstage.co.uk/home.html thanks for the advice Tony), he monitors the current going out of his generator truck and we were amazed how low the current draw for our HK projector rig was.

BTW I posted this 'cos I thought it might interest a few other people as well as eliciting some useful info for me 8-)
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Re: Generator for small PA system

Postby ef37a » Mon Jul 22, 2013 9:09 pm

Bump.

Dave.
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Re: Generator for small PA system

Postby eventpahire.co.uk » Sat Jul 27, 2013 3:23 pm

A ~2kva petrol generator such as the one mentioned in the OP is completely unsuitable for purpose.
There will be no stability in the voltage and the set is so small, it won't cope with sudden peak draw, such as when the bassline drops or loud announcements are made.
If you are intending on connecting sensitive electronic equipment, you need a diesel set with AVR (automatic voltage regulation).
For small PA setups such as this we usually specify 6kva Stephill or Hyundai AVR sets.
Also, the fuel tanks on these are large enough to run for many hours without refills.
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Re: Generator for small PA system

Postby Sam Spoons » Sun Jul 28, 2013 5:34 pm

The Kipor being an inverter generator voltage stability is absolutely assured and with significantly better accuracy than an AVR set. I do agree that it's on the small side but if you read my earlier posts (and the thread title) you'll note that the rig I plan to run is also quite small. I have done both practical tests of the gear and also calculations based on published specifications and conclude that, while running high levels of bass may cause issues (in which case I'll admit defeat and run without the sub) the genny is more than capable of running FOH, monitors and backline for my trio. A practical test running a 1500 watt electric heater alongside a Yamaha DXR10 playing loud recorded music showed the genny comfortably supplying 6.5 amps and no audio nasties.

Basically the Kipor will supply 8.7A of clean,stable, 50HZ sine wave power with voltages staying within +/- 1 volt. A diesel AVR genny will maintain stable volts but the 50Hz may vary with load hence the high rating suggested. If I was running a big rig I too would specify a big diesel genny but they are noisy, smelly, heavy and very expensive by comparison (the Kipor has a street price of £450). Also I'm not expecting to do full scale outdoor festivals with it and a run time of 3 hours on a tank will be sufficient.

When I've done the first gig with it (August Bank Holiday weekend) I will post regarding the success or otherwise of the genny, if it proves that the Kipor is unsuitable I'll gladly eat humble pie (and bung the genny on eBay). I do feel fairly confident as the rig will be two K12s, two DXR10s, Ashdown Superfly 500 watt bass head and an 18 watt valve combo, anticipated current requirement around 5 amps.
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Re: Generator for small PA system

Postby TSH-Tim » Mon Jul 29, 2013 7:34 pm

This is going to end in tears.... my advice is don't book anything from HSS and don't book anything less than 10KVA
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Re: Generator for small PA system

Postby Sam Spoons » Sat Aug 03, 2013 1:06 pm

I suspect some of us are missing the point here. Note the title of this thread. The main thing my 2KVA genny will be used for is small acoustic gigs, probably only a couple of K12s and a single DXR10 for foldback. I intend to try it on a low key outdoor electric gig later in the month (for which I have a contingency plan for power if it proves insufficient) with a bigger rig and some backline. I thought it may be of interest to others for 'hobby' gigs if it works. I know it is not suitable for proper pro gigs where a larger diesel generator would be required.
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Re: Generator for small PA system

Postby Sam Spoons » Mon Aug 12, 2013 10:39 am

I did a gig on Friday with the full rig (sub, 2 x K12s, 2 x DXR110s 1 x TS110A, DL1608). The band were a funky soul function band with everything miked or DI'd. I powered the full PA from a single 13A socket (back line/lights powered elsewhere). The power meter never showed more than 2A/600VA even with the band going flat out. It was a medium sized pub, the K12s were not limiting and the sound level were loud but not stupid. I was well satisfied as were the clients.
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Re: Generator for small PA system

Postby Sam Spoons » Mon Aug 26, 2013 4:49 pm

Well, the gig on the beach was last night and it's definitely possible for £200 ebay genny to run a small PA rig. The Kipor IG2000 powered 2 x QSC K12s, 2 x Yamaha DXR 10s, 1 x Alto Truesonic TS110A, 1 x Ashdown Superfly 500 watt bass head, 1 x 18 watt EL84 valve combo, 1 x Mackie DL1608 and two LED PAR cans and didn't break a sweat. It was my 3 piece band, (plus one for a couple of tunes) and we miked the Kick, Snare, O/H, Cajon, Guitar combo and three vocals plus 3 x acoustic and 1 bass DIs, we even had an eight piece choir do a couple of songs. Levels weren't huge but loud enough for a crowd of 350ish to be happy (and I even got a couple of complements on the sound quality). I did have a 'Homer' moment (d'oh) and left the powercon cable for the sub in Manchester (so we just did without :-). The genny ran for nearly 4 hours, used less than a litre of fuel and with Smart Throttle engaged was completely inaudible to the audience throughout. We raised £440 for the RNLI and everybody had a great time so I'd say it was an unqualified success. 8-)
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Re: Generator for small PA system

Postby tacitus » Tue Aug 27, 2013 8:37 am

Good show!

I think the posts leading up to the gig demonstrated that you'd tested pretty much everything there was to test, if not all at the same time. The only unknown was the fuel consumption on the night, and that seems to have been pretty moderate, as it turns out.

Intrigued that the genny was inaudible - was that when you were performing or at all times? Did you have the thing at the end of a long cable or was it just behind the stage?

It all goes to show that if your stuff fits in a hatchback, you don't need a lorry.
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Re: Generator for small PA system

Postby Sam Spoons » Tue Aug 27, 2013 12:09 pm

I put the genny behind the car, Mitsi Shogun which was adjacent to the 'stage', by the front wheel and about 10-12 metres from the stage right speakers and the desk. My son sat on the back of the car and it was audible but not intrusive where he was. The car shielded it from the punters and I'd say normal chatter would mask the genny noise, it was certainly inaudible when we were playing. I had 'smart throttle' engaged and it didn't seem to rise much above tick over even when we were playing. Here's a link to a pic, https://dl.dropboxusercontent.com/u/15685857/IMG_4816.jpeg I'll post some more when I get home.
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Re: Generator for small PA system

Postby AlecSp » Tue Aug 27, 2013 1:00 pm

It's another lesson for experience.

So, along with confirming that you don't need stacks of D&B to cover any gig, nor do you need a Midas Pro 6 mixer, nor VDC/Neutrik cables, nor the best mics, etc, you've also confirmed that you don't *need* a suitable genset.

Obviously, it's great to have the right/best tools for the job. But we all know that with a decent act, you can still create magic with an old Peavey PA, Behringer mixer, CPC/Maplin cables & no-name mics - run off a cheap genny. Might not be as polished as the top end gear, and probably won't perform as well, but most punters will never know the difference!
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