Mixing Live Sound

Lesson 2 of 17

Power and Electricity

 

Mixing Live Sound

Lesson 2 of 17

Power and Electricity

 

Lesson Info

Power and Electricity

And like I said before, here's a little disclaimer, this is going to be kind of geeky, it's going to be a little little intense from the math standpoint. It's really important to understand electricity before you get started, because power is what we do, everything we need to understand how power works. We're going to dive in and just really understand this is a very core concept, and then get into a little more detail as we go along. So the first thing is, what is electricity? Electricity is the type of energy when we talk about electricity coming from the wall there's sort of two different types of electrical current. There's, direct, current and alternating current direct current is basically a steady flow of electrons through a conductor, from one end to the from one end to the other. It's, basically a steady, consistent flow of electrons, alternating current, is a little bit different in that it's actually flowing back and forth in different directions. It's, flowing from positive...

to negative on alternating current, is typically what you find when you plug something into the wall. It's, your house alternating current, typically has a positive and a negative conductor that allow you to sort of, like, reverse the signal back and forth, and the reason we use alternating current and cities and you know, houses use alternating current is actually much more efficient to trance transfer electricity across great distances across lines with alternating current than direct current direct current is what you'd find in a battery like a nine volt battery has direct current see there's two poles. Once you plug in the battery, all the electrons flow from the negative side all the way to the positive side and it's just one steady stream on alternating current it's going back and forth in different directions on dh so that kind of creates a little bit of a confusing situation there's this these electrons moving around, and we want to understand, maybe more specifically, how we sort of measure that and how we see what's actually happening when this energy is passing through a conductor like a cable or wire. So a lot of people use what's called the water pipe analogy to understand electricity and here's sort of basic idea of the water pipe. Imagine that you have a big pipe laying on the ground or even imagine a garden hose is probably a little bit easier way to understand it and imagine that you want to be able to do work, so the main concept is that electricity is supposed to do work for us it's supposed to perform some sort of task it supposed to do something, and we want to take that water or electricity and make it do work specifically the work that we want to do is we want that electricity to move the speaker cones back and forth in order to get that work done we have to create electrical power um s so if you think about water traveling through a hose how do you get the water? Imagine you're standing your backyard how do you get the water to actually do work for you like let's say there's dirt on the ground on the sidewalk and you want to move that dirt how do you get the water to actually physically move it and do that work for you there's a couple different ways to do it one way would be to turn up the water right go over to the hose and turn up the the dial on the hose and actually create more water coming through the pipe so if we think about mohr water coming through the pipe the amount of water that's coming through in electricity we call that potential that's basically measured in voltage we say how much voltage is coming through if we can crank up the amount of water the water's going to move faster and we're going to be able to use that water to move something like spray something away imagine like a big fire hose there's so much water coming through that it's shooting through the other side and can actually move things, but again that's not the only thing that we can do to control what that water is actually doing. The other thing that we could do is actually restrict the size of the pipe if you think about it even if you turn the water of all the way and your pipe was this big around, you probably wouldn't be doing any work right? It would still be sort of trickling out or mabley pouring out at a rapid pace but it's not gonna be flying out the other side and actually doing the work that you needed to do so the size of the pipe has a lot to do with how much actual electrical power that you have and so in electricity we call the size of the pipe the resistance or it's measured in homes with that symbol that you see on the screen that's basically how big the pipers and so if you think about it there's kind of a relationship between how much water's coming through the pipe, how big the pipe is and how much power is created on the other side so if I increase the amount of water and keep the pipe size the same, the water pressure is going to go up and the water pressure that we called is called power and that's measured in watts so we can increase the amount of water and keep the pipes says the same and in return, we get more water pressure, water or electrical power on the other side. The other thing that we can do is keep the amount of water the same and decrease the size of the pipe, and the analogy used for this is imagine you're standing, your backyard got the hose, and you put your thumb over the edge of the of the edge of the tip of the hose, and you can spray and increase the water pressure by decreasing the size of the pipe. Basically, what you're doing is putting resistance back on the flow of water and it's increasing the water pressure to keep the flow going as the water has to come out. So now it has to create more pressure on the outside. All those things are linked power, voltage out power potential and resistance. They're all sort of, like, intertwined, and they affect each other, and it works very similarly in with electricity thie amount of power that gets created is sort of a product of the voltage and the resistance that you put back on that voltage. Now, the fourth factor that we talk about with electricity is a little more complicated the four factors called current and that's sort of like how fast the water's moving if you think about current, becomes, if you like. Make a glass pipe, and you were to look in one specific spot and see how quickly the water is moving by that specific spot that would be electrical current and basically it's having with current is it's, not necessarily the water pressure it's more how quickly it's moving, or how fast it's pulling from the source, and this becomes really important with electrical circuits, because the current dictates basically, how many, how much power you khun divide across the entire circuit? Um, you might have heard of, like, a fifteen amp or twenty amps circuit, all those basically mean, is that there's only so much current you can draw from those circuits before you're going to start to toe blow the circuit. We're going talk specifically about how that sort of effects live sound, so the main concept here tow tow, walk away from, is that you've got all these different elements of electricity, and this affects both the power that you're going to plug into power, the sound system, and also the power that's going to take the signal from a microphone through big power amplifiers and then actually push it out through speakers so it's important understand that remember, you have the potential measured in voltage, which is sort of like how much water is actually coming through the pipe? You've got the resistance or how big the pipe is on dh that's basically how much resistance is putting back on the water? And then it was a result of that you have the power or the water pressure that gets created in that's measured in watts and then finally we also use current t sort of figure out how fast the water's moving at any one point to make sure that we're not pulling too much water from one source. Otherwise the water starts to dip down and the voltage drops and then that's not a good thing. So those were sort of the four components and this is where it starts to get a little geeky because there is actually sort of a mathematical relationship between all these there's two equations that air used to sort of figure these two things out. One is called the power equation and the other is called homes law power equation basically deals with just what we're talking about. This idea that the amount of water traveling through a pipe the size of the pipe and how much water pressure is created are all related mathematically related and the actual equation says that pee is eagle t squared over r which means that the amount of electrical power that you create from a circuit is going to be equal to the amount of water or electricity squared divided by the resistance or the size of the pipe so we know that there is a mathematical relationship between water pressure the size of the pipe in the amount of water and that's how we sort of mathematics we figure that out the second equation that we use is called homes law and homes law basically says that the current or how quickly electricity is moving by one specific moment is equal to the amount of voltage divided by the resistance so if you think about the amount of water and how much resistance there is on the water that's actually the current so all these things are interconnected and there's this big wheel you'll see on the right there with the pretty colors called holmes wheel and basically what you could do with that is solved for any of the four variables so if you're trying to figure out voltage and you know power and resistance or you're trying to figure out resistance and you know power and current you khun basically find in the center of the wheel what you're trying to solve for and then see which two you already know and then you can solve for each each of those each of those variables we're not going to get into the math and practice doing this this is just to show the fact that there's a very big and very important relationship between electricity and or between power voltage current and resistance and the four of them are very closely and actually mathematically linked together on we need to understand how those work in order to understand how we're going to build and get a sound system so if you want more research on holmes law there's a lot of great resource is online there's a very good explanation of how this all works in what's called the yamaha sound reinforcement guide it's a great book that's been around for a long time that sort of describes all this so if you really want to dive deep into the math and understand more about this I'd highly recommend to go check that out so what's the big takeaway from all this what are we trying to learn electricity is flowing current and all four elements are linked and changes affect each other so if you change anything about the resistance or the amount of voltage or the current you're going to change one of the other four they're all linked and that's important to understand when we're both covering powering amplifiers and also amplifiers powering speakers so the question is what does this mean for live sound basically we need to understand how to supply power to the power amps into the consuls and we need to understand how to power the speakers and send signal and amplify it through the speakers get the electricity to do the work of moving the speaker comes back and forth which creates sound that we can hear so that's sort of like the basic intro to all of the stuff about electricity.

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!