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Thread: Enough power/electricity to run it all efficiently?

  1. #11
    In the USA, a single outlet is generally rated at 15 amps (1800W @ 120V), but the electrical code allows a circuit with more than one outlet on it to be breakered at 20A.. so they usually are breakered at 20A (2400W @ 120V). If you look at this wire size chart ( https://en.wikipedia.org/wiki/Americ...AWG_wire_sizes ) you can see that 14AWG is rated up to 15A, 12AWG is rated to 20A.. so basically you should be using a quality 12AWG cord for your initial connection between the outlet and your gear. Not only for safety, but because the smaller the cord (higher AWG), the more voltage drop you will get, which affects the performance of your gear. Amplifiers/Powered Speakers with switching power supplies in them will actually pull MORE amperage when there's lower voltage.. thereby making your situation worse so far as available amperage. So basically, using a heavier cord vs a lighter one is never a bad choice. 12AWG should be the default choice on a USA circuit, though 14 is ok for shorter cords (eg 25ft).

    As far as how much power you need.. the old rule of thumb used to be that you need half as much input power as output.. if your subs are 1500W output each (3000 total), you need 1500W of wall power to drive them. So your idea that they should be on their own circuit is correct. And everything else is probably fine on another circuit. But with new gear using mostly digital amplifiers now, which are very efficient with power, you can get more sound out of less wall power. This past weekend I had my system at a festival and we ran my system, which is usually connected to TWO 30A circuits specially connected into a breaker panel, off a single 20A outlet on a generator, and we were able to get pretty loud with it. Not full bore but loud. So with your gear you can probably run off one outlet with no problems, not for a club style event but for let's say a smaller wedding you'd be fine.. so long as you are absolutely sure you are not sharing that circuit with anything else.

    One thing to be aware of is the limit lights on your speakers/subs.. once they start blinking at all, if you increase the volume, your average power usage goes up significantly faster than it does below limiting.
    So if you're in a situation where power is a problem, stay below limiting on your speakers.
    Last edited by light-o-matic; 07-04-2017 at 09:06 AM.

  2. #12
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    Quote Originally Posted by light-o-matic View Post
    In the USA, a single outlet is generally rated at 15 amps (1800W @ 120V), but the electrical code allows a circuit with more than one outlet on it to be breakered at 20A.. so they usually are breakered at 20A (2400W @ 120V). If you look at this wire size chart ( https://en.wikipedia.org/wiki/Americ...AWG_wire_sizes ) you can see that 14AWG is rated up to 15A, 12AWG is rated to 20A.. so basically you should be using a quality 12AWG cord for your initial connection between the outlet and your gear. Not only for safety, but because the smaller the cord (higher AWG), the more voltage drop you will get, which affects the performance of your gear. Amplifiers/Powered Speakers with switching power supplies in them will actually pull MORE amperage when there's lower voltage.. thereby making your situation worse so far as available amperage. So basically, using a heavier cord vs a lighter one is never a bad choice. 12AWG should be the default choice on a USA circuit, though 14 is ok for shorter cords (eg 25ft).

    As far as how much power you need.. the old rule of thumb used to be that you need half as much input power as output.. if your subs are 1500W output each (3000 total), you need 1500W of wall power to drive them. So your idea that they should be on their own circuit is correct. And everything else is probably fine on another circuit. But with new gear using mostly digital amplifiers now, which are very efficient with power, you can get more sound out of less wall power. This past weekend I had my system at a festival and we ran my system, which is usually connected to TWO 30A circuits specially connected into a breaker panel, off a single 20A outlet on a generator, and we were able to get pretty loud with it. Not full bore but loud. So with your gear you can probably run off one outlet with no problems, not for a club style event but for let's say a smaller wedding you'd be fine.. so long as you are absolutely sure you are not sharing that circuit with anything else.

    One thing to be aware of is the limit lights on your speakers/subs.. once they start blinking at all, if you increase the volume, your average power usage goes up significantly faster than it does below limiting.
    So if you're in a situation where power is a problem, stay below limiting on your speakers.
    Thank you, this was a great write up! I've never had the issue of blowing a breaker but just the thought of it had me worried because it would really put a damper on the show. This should ease my mind a little. Of course it is very rare (only twice) that I've done a set up and a custodian, owner, etc... actually knew the layout of the electric and told me so I can plug in accordingly. And obviously I'm not going to snoop around looking for a breaker box and trying to figure out circuits. At minimum I try to use as many different outlets as possible hoping to hit on different circuits (plus I prefer to run shorter cords as it looks cleaner).

  3. #13
    Snooping around for the breaker panel is what you should do.. because if you do trip a breaker, won't you want to know exactly where that breaker is so you can reset it as quickly as possible? Else it could be a long time standing there like a deer in the headlights waiting for the people who manage the joint to be found.. only to be told that they don't know anything about it and they have to call the maintenance guy, or whatever. Really it's better to know where it is. And then half the time you find that it's not labeled very well and doesn't give you much of an idea what is on what circuit. But the other half the time you can get a very good idea from looking at the panel. But if you have to guess.. then plug one cord into the wall circuit in the room you are in, and run another longer cord into a hallway or another room. Those will usually be a different circuit. Or if there are floor pockets and wall outlets they are usually separate. You can't count on two wall outlets in the same room being on different circuits.. they usually aren't. But sometimes the panel labels will tell you eg "Ballroom B NE Wall" etc.

  4. #14
    There are tools you can buy where there's a piece you plug into the outlet and then a wand you bring near the breaker and it'll beep when you've found the right one. So you can verify what.breakers you're using.

  5. #15
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    So as a follow up and a question. I purchased a Kill O Watt tool and just for practice I plugged in my two ADJ Dotz TPar systems into a power strip, then into the Killowatt tool and then the wall. Although it fluctuated a little, they both never went above 2amps. I'll test the rest at my next gig, I did not have time to unload my trailer at this time.

    The question, is the amps being pulled what I should be focusing on? The tool has multiple readings (Volts, Amps, Hz, kWH) but if all i'm trying to avoid is blowing a breaker and getting the most out of my speakers, should I just be looking at the amperage and making sure it stays under the circuit breakers limit (usually 15amps)?

    Thanks in advance

  6. #16
    Well.. basically yea.. because the circuit breaker is triggered by a certain amount of current.. which is what the amps reading is telling you. Watts = Volts x Amps, so if you assume a standard voltage, let's say 120V, 20A would be 2400W, 15A would be 1800W. Voltages will vary from place to place slightly. But basically, 20A or 2400W is the absolute max you can get from a single USA circuit.. if nothing else is on it. But since you don't know for sure (without finding the breaker panel) if the circuit is 15 or 20A, and you don't know for sure that nothing else is on it, 1500-1800W (12.5-15A) would be a safer amount per circuit. But you can pull more than the maximum for a brief moment so if your sound spikes it higher on peaks that's fine. Different breakers handle it differently but most will handle a small overload for a few seconds if the average power you are pulling is well under.

  7. #17
    Of course if something else is using the breaker you are using, then the current that the other device is using is deducted from your maximum.
    And obviously if you have two extension cords but they're both plugged into outlets on the same breaker.. your total limit of the two cords combined is still that of the one circuit.

    But if you're in a situation where you can't know what's on what circuit, the best thing to do is run extra cords.. so, if you can get by on 1 circuit, run two cords.. and do the best you can to plug them in different places so they will probably be on different circuits. If you need two circuits, run three. So if one trips, you have backup. Otherwise, like I said, if you think you only need one circuit and so you run one.. then it trips in the middle of your gig.. the music stops.. and you don't know where the breaker panel is located.. then what are you gonna do?? It's good to have some kind of backup plan on power.

  8. #18
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    Thanks! I went ahead and ordered one of the tools that allows you to match outlets to breakers. Of course that will take me a little more pre session work but could be worth it (granted I find the box as well). My perfect world would be to run the two subs off one circuit and every thing else off another. That 'should' keep me safe. But like you mentioned, you never know if on the other side of the wall or in another room they have a power hungry device plugged in using up some of my current. I guess that's another reason I try to do a full sound check at full volume to just see what happens.

    When you talk about running two or three cords to try and get on separate circuits, do you go ahead and use them or just leave them laying ready to switch over to if need be? I would just think to get to a different room or hall you may have to run quite a length of extension cord which would hurt your electrical flow as well.

  9. #19
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    UPDATE!!!!

    So I unloaded all my gear and using the Kill O Watt tool, plugged things in individually and then as whole into an outlet. I am very confused as to what I found, am I missing something, do something wrong or is this what I should have expected???

    System was set up pin a garage on a circuit with a 30amp breaker. Nothing else was connected to circuit. Started with 'table accessories' only (laptop, mixer, fan, microphones, etc..) and tool showed .76 amp draw max.

    I then plugged in one subwoofer only into the tool and ran until it was limiting and got a max of 2.8 amp draw. Plugged both subs into the Kill O Watt tool and got a max of 4.5 amp draw.

    Plugged in to my two tops into the tool and got a 1.25 amp draw and I was cranked up pretty high volume wise but not quite limiting.

    These numbers seemed way below the limits so I tested it and plugged EVERYTHING into a power strip that was then plugged into the Kill O Watt tool. So that was all my 'table accessories', 2 JBL 18" Subs, 2 JBL tops and 6 ADJ Par uplights. Running near full blast it was only drawing 6.8 amps and around 700 watts.

    Am I doing something wrong with this test? Do these numbers seem a bit low (especially the watts) or are the on board processors so efficient now that they should be this low. I mean I pretty much ran my entire system that I use for weddings and school dances off one outlet and my numbers showed it was well below breaking point. Safe to say I'm a bit confused now.

  10. #20
    Quote Originally Posted by stlstudent View Post
    UPDATE!!!!

    So I unloaded all my gear and using the Kill O Watt tool, plugged things in individually and then as whole into an outlet. I am very confused as to what I found, am I missing something, do something wrong or is this what I should have expected???

    System was set up pin a garage on a circuit with a 30amp breaker. Nothing else was connected to circuit. Started with 'table accessories' only (laptop, mixer, fan, microphones, etc..) and tool showed .76 amp draw max.

    I then plugged in one subwoofer only into the tool and ran until it was limiting and got a max of 2.8 amp draw. Plugged both subs into the Kill O Watt tool and got a max of 4.5 amp draw.

    Plugged in to my two tops into the tool and got a 1.25 amp draw and I was cranked up pretty high volume wise but not quite limiting.

    These numbers seemed way below the limits so I tested it and plugged EVERYTHING into a power strip that was then plugged into the Kill O Watt tool. So that was all my 'table accessories', 2 JBL 18" Subs, 2 JBL tops and 6 ADJ Par uplights. Running near full blast it was only drawing 6.8 amps and around 700 watts.

    Am I doing something wrong with this test? Do these numbers seem a bit low (especially the watts) or are the on board processors so efficient now that they should be this low. I mean I pretty much ran my entire system that I use for weddings and school dances off one outlet and my numbers showed it was well below breaking point. Safe to say I'm a bit confused now.

    That is a pretty low reading but yea, if the speakers are all using class D amps (digital) then the efficiency should be above 90%.. prior to class D, the best you could hope for was around 65%.. big difference with newer gear. It depends on the music you are playing but keep in mind that music is not continuous power.. it's peaks and dips.. the killawatt is reading average power, but your amps are called upon to several times that amount on each beat and more on peaks. Limiters respond to peaks not average power.

    But a couple of things to consider in all this:

    You weren't running your system full volume. Keep in mind that each 3dB in volume decrease is halving the power. And each 3dB increase doubles the power. a 10dB increase, which is generally considered "twice as loud", represents a 10X increase in power! So "almost as loud as I can go but not as loud" might only represent half your available power.

    Your limiters might kick in early, or light when very little limiting is occuring.. or on very short peaks.. so your average power is still pretty low and you have a good amount more you can go. Again keeping in mind that a 3dB increase is a doubling of power.

    The power ratings on a lot of gear these days is a pretty ridiculous peak rating that doesn't really represent the true power you are going to get or use (except maybe for milliseconds at a time on peaks).

    Last but not least, audio power draw is complicated to measure because of the way it changes all the time.. the killawatt meter being a cheap little digital thing may not sample or integrate fast enough to get a perfectly accurate reading.

    But yea bottom line is that you can in fact get pretty loud with a single outlet. The configuration that I bring out most often these days is an EAW system with 4X dual-15 subs, 2X dual-15 tops and sometimes 2X single-15 tops in the rear.. plus two ZXA1 monitors, a mixer and CDJ's.. four amplifiers to run it all.. the sub amp alone is rated 8000W into 2 ohms which is how I am running it, tops probably running about 1500W each.. and I have run all this from two wall outlets. I don't like to.. and I don't do it when I need the full capacity.. but it's amazing how loud I can get with no problem. The sub amps are digital, the top amps aren't... Just recently I ran this setup off a 3600W generator and it quite pushed the limits but it worked...
    Last edited by light-o-matic; 07-21-2017 at 10:20 AM.

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