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Author Topic: Holy Current Draw Batman  (Read 10693 times)

Tim McCulloch

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Re: Holy Current Draw Batman
« Reply #30 on: February 27, 2012, 12:09:51 pm »

Yes, it's hard to get a good reading with music due to the dynamic content of the music fluctuating.  This is also exactly why the power the amplifiers draw from the mains while playing music is surprisingly low compared to what many assume. 

I think the message of the OP was that we can probably relax our demands for power towards venues and promoters a fair bit without running the risk of tripping breakers.

By using sine waves to "trick" the power amplifiers into drawing a lot more than they'd ever do with musical content one would be back at square one which was that "we" usually way overspec the amount of power needed to run a given system.

And over-specifying power requirements is why my firm hasn't had a mains supply issue in years.... oh shit, now I probably jinxed us.... but it never hurts to over estimate the demand.

We do hotel ballrooms and other sundry places with inadequate power.  Try finding a "facility engineer" at 6:30am on Easter Sunday... when powering up the first Macrotech 3600 trips the 20 amp breaker... and that's why we always specify a minimum of 100amp 3 phase 120v-208v. power.

YMMV, but I find that church people get anxious when they fear god's wrath from not starting a service on time.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

kristianjohnsen

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Re: Holy Current Draw Batman
« Reply #31 on: February 27, 2012, 12:13:55 pm »

paragraphs ? i was in the missippi public school system in the 60's and early 70's during all the intergration that went on. i was sent to public schools in bad parts of town. there are lots of thing i wasnt taught due to all the other stuff that went on at school. as for mentioning my buddy and posting a foto why is that a problem ? if someone else did it and made mention of some gen stuff i wouldnt mind a bit. i was just trying to help a guy out. sorry that my post bothers you.

Jeff, to be fair:  I try to be understanding when people type in a fashion that I need extra time to interpret, as there are many reasons why it can be a challenge for many people to communicate efficiently on a computer - like you allude to.

But when you write stuff like this:
you didnt read my post did you ?! i said run to "JUST BELOW CLIP" DUDE !! LEARN TO READ !!

You are not awarding me the slack that you, yourself, apparantly would like to receive from others:
paragraphs ? i was in the missippi public school system in the 60's and early 70's during all the intergration that went on. i was sent to public schools in bad parts of town. there are lots of thing i wasnt taught due to all the other stuff that went on at school.

If you were as proficient a reader as you would like me to learn how to be, you'd probably read the location right below my name.  If you are unsure, I'm talking about this place:

http://www.maplandia.com/norway/oppland/lillehammer/

English isn't our native tounge here.  For me, it's my third language.

Just for the record, I think you are a rude person for posting stuff like that.  Bad karma, dude  ;)
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kristianjohnsen

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Re: Holy Current Draw Batman
« Reply #32 on: February 27, 2012, 12:23:20 pm »

And over-specifying power requirements is why my firm hasn't had a mains supply issue in years.... oh shit, now I probably jinxed us.... but it never hurts to over estimate the demand.

We do hotel ballrooms and other sundry places with inadequate power.  Try finding a "facility engineer" at 6:30am on Easter Sunday... when powering up the first Macrotech 3600 trips the 20 amp breaker... and that's why we always specify a minimum of 100amp 3 phase 120v-208v. power.

YMMV, but I find that church people get anxious when they fear god's wrath from not starting a service on time.

Tim.

I'll certainly agree that it's better to over-specify then under-specify :).

But, if we were all to just take the peak power rating of all our speakers, multiply by 1,4 to compensate for amplifier inefficiency, convert that to amps using ohm's law; and specified that as our power needs, we'd be throwing our own and our clients' money out the window.
Somewhere in the middle of best case and worst case is probably a sound middle ground. 

It seems more and more people are realizing that the sound middle ground is a fair bit closer to the best case scenario than we might naturally assume.

Considering the nature of music, and the very construction of loudspeaker transducers, it only makes sense to me that we're not hitting these things constantly with thousands of watts for hours on end.  Look at the build of a space heater element vs a voice coil!
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RYAN LOUDMUSIC JENKINS

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Re: Holy Current Draw Batman
« Reply #33 on: February 27, 2012, 12:43:04 pm »

And over-specifying power requirements is why my firm hasn't had a mains supply issue in years.... oh shit, now I probably jinxed us.... but it never hurts to over estimate the demand.

We do hotel ballrooms and other sundry places with inadequate power.  Try finding a "facility engineer" at 6:30am on Easter Sunday... when powering up the first Macrotech 3600 trips the 20 amp breaker... and that's why we always specify a minimum of 100amp 3 phase 120v-208v. power.

YMMV, but I find that church people get anxious when they fear god's wrath from not starting a service on time.

It herein lies the problem for some of us.  My distro is single phase so I need to be cognizant of the fact that I need more current capacity than I would need if I were three phase with all legs evenly balanced.  I definitely need to step up to the plate this year and get me a three phase distro.  Our shows are getting bigger and I see the need very soon. 

It was quite amazing though how low the current draw I measured was.  So I started to do a little research about Clamp meters.  Obviously a lot of people like their Flukes but there really are over priced for what you get unless you are doing a lot of HVAC work.  I have found a competing brand that is slightly more affordable for a "True" RMS clamp meter.

While doing my research I learned that the elctrical waveforms can get distorted from certain items that are plugged into the service and this is what causes non-true RMS meters to be inaccurate in some cases.  While reading I found that a non-true RMS meter can show as much as 30-40% lower that the true current or voltage and as much as 10% higher than the true voltage or current all depending upin any wafeform distortions that may be there.  I have no idea if the typical componants used in concert production cause these distortions in waveforms or not.  After doing some comparative measurements, if I find them to vary considerable based upon types or brands of meter then I may go ahead and buy a handheld ocilloscope also to that I can view the wave forms to confirm maore data.

It seems that if looking at the wave form on an ocilloscope it shows a nice clean sine wave then the non-true RMS meter is going to be just as accurate as the True RMS meters.  When distortions show up then the True RMS meters can still be within a percent or two while the non-True RMS will start o be inaccurate.

So this little thread that I started to show how little current we are actually using has actually forced me to do a little more reading and learning which in the end is what we are all here for, to learn.

So I will be buying a new meter and will start measuring my current draw whenever I get a chance and I am going to actually make a spreadsheet to keep track of current draw, voltage drop, amplifier headroom, sound and lighting componants, etc.  so that I can truely have a better feel for what I need under different circumstances.

I have a feeling that a typical 100 Amp three phase service will go way further than I could have ever imagined in the past.  Plus now that so much of the lighting and video world is going with LEDs the demands of venue power are going down even further.
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Tim McCulloch

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Re: Holy Current Draw Batman
« Reply #34 on: February 27, 2012, 12:55:29 pm »

All I need is ONE disappointed client to bad-mouth our firm because the fucking venue has shitty wall power?  NO.

And I don't say by how much I over-spec, either.  You don't know what I bring or how much of it.  It could be that I'm only over by 20%, or it could be over by 80%.  Either way I don't have to "explain" what happened to our clients.  Why?  Because in the eyes of those whose emotional response to a power failure is that "explanation" is the same as "excuse."  If avoiding a negative company/personal impression and client unhappiness is "throwing away money" I'm all for it.

One of the reasons I personally don't do bar gigs is lousy power.  I've been embarrassed  by it a couple of times in the past and don't wish to have my name or that of my employer attached to preventable failures of any kind.

That said, I wouldn't spec 100 amp 3 phase service in a bar unless we really needed it, but for hotel ballrooms, convention/performing arts centers, multi-purpose facilities... it's worth it.

Tim Mc


Tim.

I'll certainly agree that it's better to over-specify then under-specify :).

But, if we were all to just take the peak power rating of all our speakers, multiply by 1,4 to compensate for amplifier inefficiency, convert that to amps using ohm's law; and specified that as our power needs, we'd be throwing our own and our clients' money out the window.
Somewhere in the middle of best case and worst case is probably a sound middle ground. 

It seems more and more people are realizing that the sound middle ground is a fair bit closer to the best case scenario than we might naturally assume.

Considering the nature of music, and the very construction of loudspeaker transducers, it only makes sense to me that we're not hitting these things constantly with thousands of watts for hours on end.  Look at the build of a space heater element vs a voice coil!
« Last Edit: February 27, 2012, 12:58:29 pm by Tim McCulloch »
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

g'bye, Dick Rees

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Re: Holy Current Draw Batman
« Reply #35 on: February 27, 2012, 01:08:33 pm »

Short circuit.......
« Last Edit: February 27, 2012, 02:07:54 pm by dick rees »
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Re: Holy Current Draw Batman
« Reply #35 on: February 27, 2012, 01:08:33 pm »


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