How powerful generator is needed for this PA system

Mitch Miller

Sophomore
Oct 30, 2012
121
1
16
I've been asked about providing sound for a local five piece band at an outdoor mall ... where the venue has committed to providing generator power. I'm a little concerned they (the venue, and the band, for that matter) think that means digging up a utility generator out of someone's garage and running a long extension cord. :roll: Can't say I'm very excited about the idea of hooking up my equipment to some random power supply.

Years ago I had a little Honda eu1000i generator and really liked it. Suffice to say I'm familiar with the product line and why it's desirable for a PA setup.

What I'm not really confident with, is *how much* generator do I need? I did some research here, and closest I could come with a guideline was 2x your PA's rated output.

I have a Behringer EP2000 (power consumption says 1600W, presumably max), a QSC GX5 (specs. say 6A at 1/8th power, so I'm figuring a max of 1200W), plus two guitar amps, a keyboard, bass amp, X32, laptop, and some miscellaneous items (ex: wireless mics. talkbox, fx pedals). I've run the whole works through a Kill-A-Watt, but even when the amps begin to clip (playing 80s rock), it seems like it barely hits 800W. That just seems surprisingly low.

With 2800W in amp draw alone, I really expected to need a 3000+ Watt inverter generator to safely power this setup.

I'd like to be reasonably prepared when the venue emails back with what they're "offering" for us to use.

-- Mitch

E2A - Forgot to mention that the band will also have four Alto TS112's (as monitors). While they don't give a power usage spec, they're rated at 800 Watts peak output. If one uses the 2x rated power requirement, that's another 3200W of generator!
 

Tim McCulloch

Graduate Student
Jan 11, 2011
3,011
49
48
Wichita KS USA
Re: How much generator?

I've been asked about providing sound for a local five piece band at an outdoor mall ... where the venue has committed to providing generator power. I'm a little concerned they (the venue, and the band, for that matter) think that means digging up a utility generator out of someone's garage and running a long extension cord. :roll: Can't say I'm very excited about the idea of hooking up my equipment to some random power supply.

Years ago I had a little Honda eu1000i generator and really liked it. Suffice to say I'm familiar with the product line and why it's desirable for a PA setup.

What I'm not really confident with, is *how much* generator do I need? I did some research here, and closest I could come with a guideline was 2x your PA's rated output.

I have a Behringer EP2000 (power consumption says 1600W, presumably max), a QSC GX5 (specs. say 6A at 1/8th power, so I'm figuring a max of 1200W), plus two guitar amps, a keyboard, bass amp, X32, laptop, and some miscellaneous items (ex: wireless mics. talkbox, fx pedals). I've run the whole works through a Kill-A-Watt, but even when the amps begin to clip (playing 80s rock), it seems like it barely hits 800W. That just seems surprisingly low.

With 2800W in amp draw alone, I really expected to need a 3000+ Watt inverter generator to safely power this setup.

I'd like to be reasonably prepared when the venue emails back with what they're "offering" for us to use.

-- Mitch

E2A - Forgot to mention that the band will also have four Alto TS112's (as monitors). While they don't give a power usage spec, they're rated at 800 Watts peak output. If one uses the 2x rated power requirement, that's another 3200W of generator!

Have the Mall rent a 25kw "Whisper Watt" generator with 100' of 6/4 feeder and a spider box. It will set them back about $300 including delivery.
 

TJ Cornish

Graduate
Jan 13, 2011
1,263
0
0
St. Paul, MN
Re: How much generator?

Have the Mall rent a 25kw "Whisper Watt" generator with 100' of 6/4 feeder and a spider box. It will set them back about $300 including delivery.
Here in Minneapolis a trailer-mounted generator would be a chunk more than that after permitting and setup. My go-to generator setup is a Honda EU6500 which provides 2 20A circuits on-generator (I use a small distro), and is small enough to get under the permitting radar. Rental is $135/day, but I have to transport.

Mitch, it would be worth your time to have an in-line GFCI available for safety: http://t.homedepot.com/p/Tower-Manu...e-Tap-Cord-Manual-Reset-30338024-08/202510258
 

TJ Cornish

Graduate
Jan 13, 2011
1,263
0
0
St. Paul, MN
Re: How much generator?

I've been asked about providing sound for a local five piece band at an outdoor mall ... where the venue has committed to providing generator power. I'm a little concerned they (the venue, and the band, for that matter) think that means digging up a utility generator out of someone's garage and running a long extension cord. :roll: Can't say I'm very excited about the idea of hooking up my equipment to some random power supply.

Years ago I had a little Honda eu1000i generator and really liked it. Suffice to say I'm familiar with the product line and why it's desirable for a PA setup.

What I'm not really confident with, is *how much* generator do I need? I did some research here, and closest I could come with a guideline was 2x your PA's rated output.

I have a Behringer EP2000 (power consumption says 1600W, presumably max), a QSC GX5 (specs. say 6A at 1/8th power, so I'm figuring a max of 1200W), plus two guitar amps, a keyboard, bass amp, X32, laptop, and some miscellaneous items (ex: wireless mics. talkbox, fx pedals). I've run the whole works through a Kill-A-Watt, but even when the amps begin to clip (playing 80s rock), it seems like it barely hits 800W. That just seems surprisingly low.

With 2800W in amp draw alone, I really expected to need a 3000+ Watt inverter generator to safely power this setup.

I'd like to be reasonably prepared when the venue emails back with what they're "offering" for us to use.

-- Mitch

E2A - Forgot to mention that the band will also have four Alto TS112's (as monitors). While they don't give a power usage spec, they're rated at 800 Watts peak output. If one uses the 2x rated power requirement, that's another 3200W of generator!
Peak amplifier power isn't the right number to use for power consumption - the 1/8th power number given in amps is a better place to start. For your non amplifier gear, you can add up the current or wattage as those are continuous draw items. Then add a little headroom.

You would likely be fine on an EU3000, but for headroom and to Tim's point about larger generators usually not being much more expensive to rent, the EU6500 may be the right choice. If your city is more like Wichita and/or the mall is paying for it, Tim's proposed setup would be better and more turn-key to you. Whatever you do, measure the power before you use it - particularly when on a generator.
 

Robert Piascik

Freshman
Mar 1, 2012
68
0
6
Hilliard, OH
Re: How much generator?

If you're asking "how much" the answer is generally "more", in my experience. I agree with both answers above: either a minimum 20kW diesel or the big Honda inverter ought to do the trick and should only cost $200-$300 to rent. There always seems to be someone willing to donate use of their gas powered something and counting every watt and claiming "this ought to be big enough" and if not "we can get a second one" and now you're competing with the sound of two lawnmowers located right behind the band. I've never seen it work effectively. Five piece band playing outdoors? I wouldn't go with anything less than the two listed above.
 
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Robert Piascik

Freshman
Mar 1, 2012
68
0
6
Hilliard, OH
Re: How much generator?

Many times I rent and bring the diesel generator myself. I have a big pick up truck and the ability to tow it myself, I have an account with the local Sunbelt equipment rental and own a distro box. I charge the same as Sunbelt would if it included delivery but *I* make the the cost of the delivery and the rental of the box and I save the client the hassle of doing it themselves. I add in enough to cover the fuel upon return and a few bucks for your trouble and make it a flat rate. (And if they don't like the price they are welcome to do it themselves.)
 

Ben Gingerich

Sophomore
Oct 19, 2012
188
0
16
Warner Robins Ga
Re: How much generator?

Peak amplifier power isn't the right number to use for power consumption - the 1/8th power number given in amps is a better place to start. For your non amplifier gear, you can add up the current or wattage as those are continuous draw items. Then add a little headroom.

You would likely be fine on an EU3000, but for headroom and to Tim's point about larger generators usually not being much more expensive to rent, the EU6500 may be the right choice. If your city is more like Wichita and/or the mall is paying for it, Tim's proposed setup would be better and more turn-key to you. Whatever you do, measure the power before you use it - particularly when on a generator.


Also MAKE A PATH TO GROUND, i know alot of people say its not needed, but if you want any of that great gear/human protection these generators claim, than you need a path to ground, it can be a wire that you put on a small metal tent stake in the ground BUT HAVE SOMETHING!
 

Phil Graham

Honorary PhD
Mar 10, 2011
651
1
18
Atlanta, GA
Re: How much generator?

Also MAKE A PATH TO GROUND, i know alot of people say its not needed, but if you want any of that great gear/human protection these generators claim, than you need a path to ground, it can be a wire that you put on a small metal tent stake in the ground BUT HAVE SOMETHING!

Ben,

A path to ground via Generator ->GEC -> Grounding conductor is not a safety component for portable generator systems. Indeed the NEC in article 250 specifically excludes this as a compliant ground fault return path.

The bonding between the neutral and the EGC at the genset provides the fault current return path to trigger the OCPD.

Bonding of the GEC/GC pair to the EGC, Neutral, and genset frame at the generator does not provide the fault current return path. The grounding conductor serves to hold the bond point at a potential that matches the local earth potential.
 

Ivan Beaver

Graduate Student
Jan 11, 2011
2,300
10
0
Atlanta GA area
Re: How much generator?

Ben,

A path to ground via Generator ->GEC -> Grounding conductor is not a safety component for portable generator systems. Indeed the NEC in article 250 specifically excludes this as a compliant ground fault return path.

The bonding between the neutral and the EGC at the genset provides the fault current return path to trigger the OCPD.

Bonding of the GEC/GC pair to the EGC, Neutral, and genset frame at the generator does not provide the fault current return path. The grounding conductor serves to hold the bond point at a potential that matches the local earth potential.
BUT PHIL_ Don't you know that putting a ground rod in will automatically get rid of any noise in the system? That is what "The tour guys" say ;)

I have heard that many times. It is amazing what "rumors" get passed around in this industry. Most are based to stickly heresay and have no merit.

Passed around by people who don't know enough to realize they don't know very much.
 

Marjan Dobelsek

Freshman
Aug 8, 2014
3
0
0
40
How powerful generator is needed for this PA system

We're going to have an open-air gig where we'll have to use electrical generator to power up our system. Here's the list of equipment we plan to use:
- 2x EV ZLX12P
- 1x FBT MAXX10SA
- notebook with MIDI controller (source of music)
- 2 or 5 channel mixer
- lightmaxx cls-3


I was wondering how powerful electrical generator should we get in order to make sure there won't be any problems? Where's the bottom end line in specifications? Could we actually damage the equipment if generator wouldn't output enough power?
 

Tim Duffin

Armchair Instigator
Mar 3, 2011
125
0
16
42
CA
Re: How much generator?

You want PLENTY of generator headroom so it's just setting there loafing along during the show. Just as in power amps you want headroom on the generator.
A couple of people rounding up a few a random generators to power the system is a bad idea!!!

Correct. In my experience, if your generator isn't diesel and on a trailer, there is no way it can run ANY sound system. And if it does, it sucks. I have actually stalled a 30kw whisperwatt with a 35kw sound system before. Specifically speaking, some amplifiers cannot be used with a small gas generator at all-- crown XTI for instance cannot work, they will shut off and claim "PWR FAIL" (or some error like that, I can't remember exactly) on the screen. This is especially true for outdoor festivals where it is guaranteed that someone will plug in a power strip to your generator and run their microwave oven from it.

I bought my own 75kva diesel just for this purpose and will not do a festival unless the guys also rent MY generator. Strangely, I make more money renting my diesel generator than renting the sound system.
 
Re: How much generator?

Just yesterday I did a festival and part of deal was they had to supply a 90KW CAT generator. Yes I had a lot of extra headroom on that generator but it ran all day with never an issue running both the sound system and the 20 500 watt
par 64's that were full on all the time.

That said at the same festival I did the small side stage with a small system powered with one of the new Honda 7000 watt generators. Program on that stage was light music and spoken word.
 

Bennett Prescott

Just This Guy, You Know?
Staff member
Jan 10, 2011
10,853
29
48
37
Wallingford, CT
www.bennettprescott.com
Re: How much generator?

Peak amplifier power isn't the right number to use for power consumption - the 1/8th power number given in amps is a better place to start. For your non amplifier gear, you can add up the current or wattage as those are continuous draw items. Then add a little headroom.

Do you think the generator generally has enough mass to account for peaks, so that you can guess at a long term power number and ignore them? I would have thought the opposite, that for audio loads the genset should likely be sized to rated amp power to keep from stalling it with sudden draw. I am no expert here, though, as I have never run a PA on anything smaller than a 35kVa diesel trailer mount.
 

Jay Barracato

Graduate Student
Jan 11, 2011
1,528
2
38
Solomons MD
Re: How much generator?

Do you think the generator generally has enough mass to account for peaks, so that you can guess at a long term power number and ignore them? I would have thought the opposite, that for audio loads the genset should likely be sized to rated amp power to keep from stalling it with sudden draw. I am no expert here, though, as I have never run a PA on anything smaller than a 35kVa diesel trailer mount.

I feel like this has gotten to the same stage as "how much PA do I need?" Most of us, based on experience, have paid the lumps and can look at a space and picture how much PA we would put in there for different types of events. And we know if we ask others, we are likely to get a range of answers with the usual outliers on both extremes. Maybe that room isn't going to sound very good with a pair eons that cousin Elmo can borrow, but it also doesn't need 12 vertec per side. Somewhere in the middle is an answer that is "enough but not too much."

I look at generators the same way. While just get more than enough is an easy answer, it is not always a cost effective one. A friend of mine was getting married and the event was going to be in a large tent on a friends farm. They were going to use a couple of cheap construction generators but wanted to pay me a goodly chunk for providing sound for several bands that were going to be performing. I volunteered my services for free but insisted they rent a proper generator.

When I arrived onsite to setup, they had already strung numerous lights everywhere, had a full sized carnival popcorn machine going, and had rented a full hard sided trailer rest room. In other words they had the usual chain of triple taps plugged into other triple taps with the cheapest Walmart orange extension cords running all over the place. They had already maxed out the courtesy outlets on the generator.

Fortunately I was able to plug in a 50 amp rac pak via one of the california connector circuits for my needs.

I have successfully run the same system (with no apparent change in performance) off of a EU3500. I know others have done the same. In a way it makes sense to own or rent from a trusted source to remove the vagueness of maintenance, etc. and to control access to generator during the show.

I had an entire stage shutdown on me at a major festival. I was just a visiting band tech but the system tech grabbed the chance to go get a meal. Stage went dark, band kept playing acoustically to the light of cellphones while I traced the feeder back to the panel. The generator was running fine. A GFCI had popped. Near as I could figure out, someone had plugged in an electric scooter to charge. Everything was fine while it was charging. When the battery was fully charge it then popped the GFCI.

I know my logic is akin to build a bridge, drive successively heavier trucks over it until it collapses, then rebuild the bridge and you know the weight limit but...
 

TJ Cornish

Graduate
Jan 13, 2011
1,263
0
0
St. Paul, MN
Re: How much generator?

Do you think the generator generally has enough mass to account for peaks, so that you can guess at a long term power number and ignore them? I would have thought the opposite, that for audio loads the genset should likely be sized to rated amp power to keep from stalling it with sudden draw. I am no expert here, though, as I have never run a PA on anything smaller than a 35kVa diesel trailer mount.
All generators have some peak capacity, both from the rotational inertia of the generator, and in the case of inverter generators, some small amount from the inverter circuitry. Guy Holt wrote in a very long thread about inverter generators' ability to handle more loads than a conventional generator at the same rating in some cases, and his findings that the EU6500's inverter is actually capable of 7680 watts continuous output.

Inverter generators are less sensitive to non-linear loads (explained in the first link above). Additionally, when an inverter generator is hit with a dynamic load, the frequency remains stable, and voltage regulation is likely better as well, since the inverter circuitry reacts much faster than the conventional engine governor. When you hit a conventional generator with a dynamic load, the engine slows which causes the frequency to fluctuate, as well as whatever voltage consequences there are.

I did an outdoor show last Saturday with 3 ITech 12000HD amps, 4 Mackie SRM450s, and light back line on an EU6500. I wasn't pedal to the metal, but it was outside and going pretty good. I ran the ITechs at 240v and all the Mackies off one leg of the generator (only had one inline GFCI adapter with me), and had absolutely no problems. The generator usage meter was showing about 3500 VA when I looked at it at fairly full volume.

My ITechs are PFC amps and an argument could be made that they're easier on generators than some other amps, but nonetheless, they're pretty big dog amps and know how to consume power. I'm sure if I hit the rig really hard I could get in trouble on the EU6500, but I did a decently loud show with a system significantly larger than the OPs on 1/2 to 2/3 capacity of the EU6500.

I'm in Jay's camp that while it's all well and good to demand a 200KVA trailer generator for a backyard barbecue, that's not always practical. A successful business person will figure out how to make the show go on, safety issues excepted. In the case of my example gig, that was a $135/day eu6500 rental vs. $900 for a delivered, permitted, and setup 25KW diesel.

Also keep in mind that turning your system down 3dB will cut your power consumption roughly in half.
 
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