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Author Topic: Specified vs Actual Power Consumption?  (Read 7077 times)

Oliver Giving

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Specified vs Actual Power Consumption?
« on: June 06, 2011, 07:54:14 pm »

Hi Folks,

Thanks in advance for your help.

I bought my first rig recently and the total wattage is 4800.  This includes both of my tops, subs, my rack, mixer, everything. 

4800 watts = 40 amps so in theory my rig should need 3 separate circuits to power it.  I've done testing at various venues and have found that I can run everything at very high volumes off of one circuit and everything is fine power wise.  I have never tripped a breaker.

From these experiments it is obvious to me that the specified wattage draw of each piece of gear isn't what it actually is.  I'm wondering if anyone here has any insight into this?  Are power consumption specs referring to, perhaps, the power drawn when the piece is turned on but not during normal operation?

I would love to know how much power my rig is actually drawing.  Does anyone know how to figure this out?

FYI my rig is ::

- 2X RCF ART-715A loudspeakers :: 750 watts each
- 2X RCF 905-AS subwoofers :: 1000 watts each
- 3X RCF ART-312A monitors :: 350 watts each

- Furman M-8DX power conditioner
- RANE ME 60S graphic EQ (monitor system)
- DBX AFS224 feedback suppressor (monitor system)
- RANE DC 22 compressor/limiter
- Aphex 204 Aural Exciter
- DBX Driverack 260 loudspeaker management
- RANE Mojo compressor/limiter

Oliver
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Oliver Giving
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Probiotic Soundsystem
Audio Visual Production for Live Community Audiences
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www.probioticsoundsystem.net

Paul G. OBrien

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Re: Specified vs Actual Power Consumption?
« Reply #1 on: June 06, 2011, 09:30:15 pm »

What you got to understand is that music is a very dynamic signal compared to an AC power sinewave and every piece of electronics has some amount of energy storage capacity so music power will never ever be equal to AC wall power draw, music power will always be the larger of the two numbers. For amplifiers and powered speakers get out the owners manuals and look up the maximum power consumption figures, you'll likely find that these devices only consume about 1/2 as much AC power as you would think, and power draw of all the rack equipment is mostly insignificant. 


« Last Edit: June 06, 2011, 09:33:18 pm by Paul G. OBrien »
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Fernando Lopez

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Re: Specified vs Actual Power Consumption?
« Reply #2 on: June 06, 2011, 09:37:36 pm »

Get this:

http://www.amazon.com/P3-International-P4400-Electricity-Monitor/dp/B00009MDBU/ref=sr_1_1?ie=UTF8&qid=1307410450&sr=8-1

Last weekend I measured 3 EV CP4000S, 1 EV DCOne, NS7 and a laptop amps and the power draw was around 15 amps

I've also measured 2 RCF art310a and 2 RCF art905as + mixer, CD players and a laptop and at full blast power draw was about 7 amps

It has been very handy
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Oliver Giving

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Re: Specified vs Actual Power Consumption?
« Reply #3 on: June 07, 2011, 06:26:37 pm »

Thanks for your help guys.  Much appreciated!
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Probiotic Soundsystem
Audio Visual Production for Live Community Audiences
C: 604.655.8840
www.probioticsoundsystem.net

Greg_Cameron

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Re: Specified vs Actual Power Consumption?
« Reply #4 on: June 07, 2011, 07:33:21 pm »

For amplifiers and powered speakers get out the owners manuals and look up the maximum power consumption figures, you'll likely find that these devices only consume about 1/2 as much AC power as you would think, and power draw of all the rack equipment is mostly insignificant.

The amount of average current draw for live sound applications is usually well under even half the maximum possible with sine wave reproduction even when running into some clipping. I state average because the short transient peaks can be much higher than average but will not stress breaker or the wire. I use old school Crest Pro amps which aren't considered very efficient. I can run all the amps at minimum rated impedance so they're pulling as much as they can. I can run the rig full tilt with monitors, back-line, and FOH all off of one dual pole 50A breaker and not have to worry about tripping it. If you add up maximum current draw just for the main speaker amps based on the spec sheets, it comes out to over 200 amps. In reality, I'm probably only pulling an average of 20 amps per leg, maybe 30 max for 40 to 60 total amps of draw when really hammering the rig. Never popped a breaker. The bottom line is that the 1/8 to 1/3rd power specs are the reality. Most amps couldn't really put out their full power very long with sine wave signals without thermaling out and shutting down. The newer class D type amps don't seem to do very well with full power sine waves before shutting down or throttling themselves way back. It's probably inconsequential though with real music signals.

Greg
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Cameron Pro Audio

Greg_Cameron

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Re: Specified vs Actual Power Consumption?
« Reply #5 on: June 07, 2011, 07:37:23 pm »

Get this:

http://www.amazon.com/P3-International-P4400-Electricity-Monitor/dp/B00009MDBU/ref=sr_1_1?ie=UTF8&qid=1307410450&sr=8-1

Last weekend I measured 3 EV CP4000S, 1 EV DCOne, NS7 and a laptop amps and the power draw was around 15 amps

I've also measured 2 RCF art310a and 2 RCF art905as + mixer, CD players and a laptop and at full blast power draw was about 7 amps

I wonder if the draws were really even that much. Those type of current measuring devices aren't well suited to dynamic drawing device like power amps with a music signal. The sampling intervals are likely not correct. They're intended for more linear draw devices like home appliances. You need a real ammeter that can do both long term and peak draw reading to really know what's going on with PA.

Greg
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Cameron Pro Audio

ProSoundWeb Community

Re: Specified vs Actual Power Consumption?
« Reply #5 on: June 07, 2011, 07:37:23 pm »


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