Mixing Live Sound

Lesson 3 of 17

Power Distribution

 

Mixing Live Sound

Lesson 3 of 17

Power Distribution

 

Lesson Info

Power Distribution

So let's, talk briefly about power distribution in the video we're going to see in a little bit you're going to see how it destro system is actually set up at a at a venue, we're going to show you the generator, how it feeds electricity to the power distribution box and how we create different circuits and sort of how it's mapped out on dh then you'll start to see how some of this math becomes practical, how you can actually use it. The first thing to understand is that there's basically two types of power that you can you'll typically see at any venue, whether it's a physical venue or whether you're running a generator or whether you're at a huge arena, understanding power is really important for the most part at any real venue or any when I say real venue, I mean, venue that follows, you know, city regulations, any sort of festival you're probably not going to deal with actually providing the power. It's it's pretty much common that onda required that electrician's actually set up an...

d provide power to your distribution box so you shouldn't have to worry about actually going into a venue and rearranging or doing anything with their internal power system. In fact, I would highly recommend that you don't do that, they should have an electrician's do that. But there are situations where you need to understand what kind of powers being supplied to you and what a venue has to supply before you arrived here before you show up with the sound system so that you know what type of electricity you're going to need it how you're going to convert that to get what you need out of it. Um so there's two different types there's what's called single phase and three phase circuits, so we're going to talk about the difference between single phase and three phase we're gonna talk about circuit amperage or basically different types of circuit breakers and what their ratings and limits are on going talk about grounding and ground loops, which is a really, really big thing for sound toe understand what ground loops are and how to prevent them it's kind of important topic so um first thing let's talk about a power circuits single phase power a single face power is most commonly what you'll probably see it any residential or commercial facility whether it's a house, a music venue, a church, a any sort of like you know this place where people go you're probably going to see single face power three phase power will get into in a second is usually what's used to feed the bigger grids, but by the time that electricity gets down to your house, it's usually been converted to single phase so what a single face power. It basically means that you have two legs of hot alternating current one neutral in one ground I'm gonna go back for a second. You see there's four pins connected to the back of this power distribution box if you see the green in the red are both hot the white or the black is ground and the white is neutral eso all four of those those pins you basically have to two hot leads on door too hot legs at ground in a neutral and the reason that you have two hot legs is once it gets to your house it comes to your house at two hundred eight volts between two eight two eight to twenty on dh each of those legs usually gets split in half and then you have one hot leg and one neutral leg for half of the house and one hot leg and one neutral leg for the other half of the house and so you have one hundred twenty volts on this half of one hundred twenty volts on this half. Um that works great mostly for houses, things like lamps and microwaves and stuff like that but if you need more power you can actually take both of those legs and combine them and you have two hearts and with two hearts you have two hundred and twenty volts of power on dso typically, power is coming in, electricity is coming in and alternating current on each of those hot legs and the reason it's called single face power is it's one single cycle of power you have won phase that's coming in it's alternating between those two hearts in three phase will talk about there's actually three three different circuits, but we'll get into that in a second. So the electricity comes in just like it would any other sine wave. It alternates that usually fifty or sixty hertz, and that electricity is coming in two hundred eight volts, which we're going to use in this example from the generator. It could be in some residential facilities up to two hundred fifty volts, but those come in and like I said, he gets split in half on either side, and then what we can do at a venue is take those four legs, those two hot legs to ground in the neutral, plugged them into a distribution box and create our own circuits so we can split off half of those to go to one hundred twenty volts circuit or use both hot legs to go to a two hundred eight volts circuit, which we'll use to power both the consuls and the speakers and the axe. Like I said, this is the most common type of power that you'll see at most venues just to sort of cover it we're not going to spend too much time on this, but just so you know about it there is something called three phase power and that's a little bit different there's actually three hot legs instead of two hot legs and what happens is that you actually have three separate cycles of electricity they're coming in on all three are slightly altered by one third of the complete cycle and the reason for that is is a lot of industrial applications require that the peak voltage or when the sine wave reaches the top on ly happens once per cycle and the rest of the time it's not hitting the complete maxim amount of voltage for the cycle and so it's not enough to power things like big motors so with three phase circuits they have three separate sine waves that are all coming in slightly offset so that for every single cycle you have three peaks instead of just one peek. Like I said, we're not going to spend too much time in this that's just sort of the main difference a lot of these air used in electrical grids, so like when they're sending electricity from the huge, you know, electrical distribution plans out to the cities they use three phase power and then when it gets to the top transformers your house, we'll split it down the single face um it's more efficient? Sometimes you can send electricity, cross larger areas you could do a lot more power with with that type of electricity. So sometimes that's how that use, like I said, just knowing if you're going into a venue and you're providing a sound system or you're working at a venue, whether it's single face power three phase power is important to understand on dh to know how to convert that to your system that you're going to be using. Okay, so let's talk about circuit and bridge. Every circuit in the electrical grid has it's own circuit breaker with a maximum current load. So if you ever go to your house and you pull up your circuit breaker, you have all little switches. Each one of those breakers is a separate circuit that's rated at a certain current maximum load. And what that means is that if I have a twenty amps circuit, for example, anything that's plugged into that circuit cannot exceed twenty amps at any one specific time. Otherwise, that circuit will blow things in your house that you would think that might pull a lot of current. They use a lot of, like, pull a lot of electricity at once would be things like your washer, your dryer probably. Or microwaves things that like have a quick burst of electricity. Those things can often pull current really quickly for at least one specific time and can blow the circuit. This also happens with sound systems, so it's really important to understand what components in your sound system going pull the most power the most quickly and isolating those on their own circuits that that they don't blow the rest of the load for everything else on the circuit is really important things to think about that actually pull a lot of electricity pull a high current load um typically powered subwoofers anything with a lot of low end if you can imagine that you're setting up for a big show and you've got huge subwoofers on the front of the stage, which will show and you know the maximum amount of current that they draw the show's going pretty quietly get pretty smooth because it's not allowed band. But then all of a sudden the band comes on with a deejay that has a huge bass drop in the role of a song and just the right time that base hits and suddenly the subwoofer peaks in the amount of voltage that it's pulling from that current because of that huge amount of electricity is going to need to move that huge speaker back and forth suddenly that current goes above the current load and can blow the circuit it happens a lot happens very often when circuits are not designed to understand how many certain how many speakers and consoles should be on their own circuit, so understanding and calculating and we're gonna walk through howto actually sort of figure this out and how we set it up. Um, understanding the maximum current load of every circuit is actually really, really important. This is a practical takeaway when you're setting up a sound system, knowing the maximum current for every circuit and distributing that across the whole system is a super, super important part of mixing live sound before you ever even start loading on stage. So that being said, we're going to watch a quick video. Now that kind of recaps everything that we've already talked about, that this actual festival you'll see us walk through the jeannie, uh, generator providing power to our power distribution system and then sending that out to each of the speakers and also out to front of house and to monitor world. So check this out. So the most important thing when you're talking about sounds, you need electricity, you need power with power, the speakers, the subs, the lighting, the consul's, everything needs power, so when we're outdoors, obviously probably generators were going to go and take a look back stage we're gonna show you what type of power were using how it gets split up what sort of distribution we need as faras destro box tto create the different circuits that we need so let's take a trip back stage so this is our super quiet generator it's actually specially ordered just to be extra quiet backstage it's giving a single phase power of two hundred eight volts and this generate actually feeds all the different destro boxes used for lighting used for stage and use for sound so it runs four separate legs too hot a neutral on the ground and each of those go to east distribution box which we pick up and then send individual circuits to whatever we need on the stage so let's go take a look at our distribution box so you can see the lines coming from the generator here in each of these feed into the district boxes for everybody's electrical set up this is the lighting company set up and this right here is our destro box. If you can look back down here you can see each of the four poles that were using there's red, black, white green so too hot a neutral on the ground those all feed two hundred eight volts on single phase power into our destro box and then from the destro we have separate circuits that come out one for subs, one for each main one for front of house, one for monitors and one for stage. So we have six total circuits that were running separate circuits that are each on their own breaker. Eso if the subs for some reason and of getting blown the rest, the all the other circuits stay up, we can flip the breaker back just on the subs. It's really important to understand and know exactly how much amperage each of your speakers in each of your circuits are gonna draw so that you don't overload any circuit typical. You have either fifteen, twenty or fifty amp circuits so it's really important to know the net. Amperage, um, of everything in your circuit to keep it under the total ambridge limit. Otherwise you're gonna blow that circuit so each of these circuits get run. The front of house actually gets run over, speak on on our snake all the way back to front of house. The monitor rig just gets run right up here and then we have stage drops you can see sort of like sprinkled around the stage for each of the musicians. We have direct lines that run specifically from here to the subs and then up the trust to the speakers on either side for both left and right so this is how we patch both signal and power to the mains. Each of these elements have their own amplifiers and crossovers built in s so we know exactly the specific amount of ambridge eats each speaker needs. So power comes up from the destro here to the very top element and then it's basically just daisy chain. We patch both signal via xlr here and, um, power comes straight down just jumping from each element. Each element. I'm all the way to the end. One thing we do too, as we mark off with tape once we get the speakers set exactly with the bottom of the rig is so we know the exact height, which is that piece of white tape right there. So we know that's when we set the speakers up yesterday where throw is gonna be the most optimal, as you can see that's basically our setup setting, running everything from the generator all the way to the speakers themselves. So let's, just kind of recap that a little bit. Here you've got the genii are the generator it's supplying two hot legs, a neutral in the ground to the power distribution box, and then we have our subwoofers on their own circuit. We have both left left and right of the line, a razor on their own circuit. We have all the stage drops on their own circuit way have the monitor console on its own circuit, and then we have the front of house consul on its own circuit. The other thing to understand about the monitors is that, um, if you have powered monitors on stage, you should power those all off the same circuit as the monitor console. And if you have amplifier racks, you should also account for every single amplifier. So this is our typical power destro scheme let's. Now look to see what kind of amperage were actually drawing from each of these. So let's, just start with front of house that's the easiest consuls are very low power. They take, um, not a lot of electricity to power the pre amps and each of the screen the led. I mean, all that stuff is really low computers. Those kind of things don't really draw a lot of power. So two amps, I'm not really worried about that. I could put that on the twenty eighth circuit just to be safe. There's probably other things will have it from a house that I might want to plug in. Um, all those things could be set up, but I'm not concerned about it. The second let's look at the subwoofers on dh when measuring amplifiers and speakers. You can look in the specifications to see what their current is going to draw, and you'll typically see that there's some times three different currents there's what's called on and they're all a lot of times called different things, but often you'll see long term current draw with no signal so that's basically the speakers are idle, they're turned on their drawing some current, but they're not actually moving speakers back and forth there's no signal coming through, you'll have a nominal signal draw or median single drive depends on what they call it that basically means like at typical program level, with the speakers moving back and forth over a long period of time, what's the what's, the maximum out that you'll see, and then you'll have instantaneous maximum current drawn that shows that if you were to just completely max out the signal input and pushed the amplifiers hard as you can for one second and you see that big spike and current what's that going to be it's really important that you make sure that when you're measuring the amperage, you're looking at the maximum instantaneous current draw because those the situations where you end up blowing a circuit if you're looking at the long term current draw and suddenly there's a big peak. Because of a big kick drum hit or a delayed drop or something, and the speaker pushes really hard and it goes way above the nominal line that's when you typically end up blowing a circuit, so make sure that when you're measuring out your circuit, you know that the instantaneous, uh, amperage draws the one you're specifically looking at, not the long term program draw s o thes subwoofers, they typically stay around four amps, but they can go up to ten amps instantaneously, so I'm going to go ahead and put each of those on their own circuit tenants, each leaving twenty amps total on the circuit, and I would probably put them on a fifty am circuit just to be safe, but we'll get into that in a second, um, mains left and right, we typically have a, um each of those elements has draws a peak maximum instantaneous current of four amps it's like four point one, I think, and if you look and count their seven elements so each one of these you can count from the top, each element draws four amps times seven the entire circuit then could draw up to twenty one amps, so I'm going to put each one of those on a thirty am circuit it's, much less likely over long term period of time. With with four inch speakers that aren't drawing subwoofers that you see instantaneous peaks as much subwoofers where you really worry about so you don't need to plan for a lot of as much over ages you would for subs so I don't need to put those on a fifty am circuit I'll put each of those on a thirty amps circuit um one for laughed and one for right stage it's important stage to keep to make sure that each of the stages have have have drops I'm sorry each of musicians have drops all over the stage to plug in there guitar amps, their keyboards they're guitar pedals all that kind of stuff on dh you never know what kind of amps someone's gonna bring every band every time of mix it a festival you'll see a band show up with a huge you know, like pro reverb or, you know, twin reverb where you have massive output tubes that draw a lot of power to vamps typically draw a lot of current or can instantaneously draw a lot of current um so having at least thirty amps on stage available for all the musicians of super important to make sure that if they do bring big power amplifiers that they're powering their base cabs with like a big svt or a big twin reverb that it's not going to draw too much current and below the stage power um let's see so we've got thirty amps on stage the next we're going to calculate each of those power amplifiers which power all the speakers if you're not using active powered speakers um each of those amplifier axe draw or am pliers in the rack draw six point three amps per amplifier so if you calculate four of those amplifiers you're looking at about twenty five amps plus again, you have about two amps for the console, so you definitely want to make sure that those anne fires are on a thirty amps circuit as well. So that's the total current travis's haman is sort of like play this out in my mind as I'm setting up and if we look here, then we'll have a fifty m circuit for the subs to thirty amp circuits at two o eight votes for the mains fifty amp circuits that one hundred twenty volts for the stage, fifty amps, four monitors and twenty amps for front of house um so on my circuit breaker on my power distribution box, I'm gonna count how many of those I have and I'm gonna run power to each of those locations with those specific power requirements and that way I know exactly how everything is distributed right now just on everything we've come so far I just want to encourage guys to ask any questions that you have, so um let's see have a question here, says hello. I usually run sound at bars were the classic setup is a bunch of fifteen and standard plugs cluster together. How do you handle this? How do you find out what they have? Usually the bar owner has no idea that's a great question, and that definitely happens. You show up to a club and you don't know where everything is on a separate circuit. Typically, the best way would be to ask if the bar owner, if he knows where the circuit board is, like where the actual circuit breaker is on dh to plug something like a lamp or something in until I get there in plenty of time in advance and find out what circuit breakers on. If he lets you do that on dh, turn off the circuits until you find it on this let's. Find what circuits are on the circuit breaker. If it's not labeled, hopefully it would be labeled on dh. Then you can actually see how many it's usually it's written on the actual breaker itself. What it's rated at so typically it's it's. Hard to sort of find those things if it's not your venue and it can be, you know, somewhat dangerous if you're not an electrician's, but if you if you could just get access to the circuit breaker when no one's there or before anyone gets there just to sort of figure out what circuits on that's usually the best bet that way you can at least see how many how many circuits you're dealing with? Um, aztec audio says can an old to vamp with poorly or faulty wiring caused the stage drop circuit breakers to trip that's a good question it's possible that they could have, um, improper grounding, which would cause, uh, jumpin amperage that would be pretty dangerous. It would have to be pretty bad wiring we're in the second going talk about grounding on dispense specifically with hand wired to vamps grounding can be a really tricky issue and could be somewhat dangerous, so we're gonna cover ways to prevent that and make sure that you're staying safe, but typically I don't think I've ever seen a tube amp specifically break a circuit if it is actually the tube amp that's causing it to break, then there's something wrong with the way the two map is wired ondas pulling way too much electricity unless it's a really low rated circuit like it's, a tenant circuit and something else there's a lot plugged into that circuit as well

Class Description

Mixing Live Sound can be one of the most daunting tasks for any engineer. In this class, Zach Varnell will walk you through the entire live sound production workflow, from loading in a PA and rigging and flying speakers to soundcheck and mixing on the fly.

In this class, you will get to see an entire day of load-in from Seattle's Capitol Hill Block Party along with a complete breakdown of a live sound production workflow and interviews with some of the country's top touring live sound engineers. You will learn:

  • Scaleable components of a live sound PA
  • Power distribution and management
  • Tuning speakers with a SMART system and FFT analysis
  • Mic Placement and tips for an effective soundcheck
  • Mixing front of house
  • Mixing for stage monitors and in-ears

We'll also walk through a live mix setup and interview with two touring engineers from their FOH mix position: Adam Jackson and Andy Frost (FOH and Monitor engineers for Christina Perri) and Shane Bardiau (Twenty One Pilots).

Whether you are a working live sound engineer and just want to brush up on some core concepts or you are a new engineer looking to get into live sound production, this is the place to learn all about live sound in one location.

Reviews

user ee67bf
 

A very good overview of live sound presented by a professional sound technician. Good supporting video of a real event that Zach worked. He explained everything very well and I enjoyed the split screen views of his console work. Good job.

Cary Knoop
 

Extremely useful class and great presentation!