Delivering enough high quality power to your marching audio system is paramount to achieving great and consistent sound quality. Oftentimes, though, it's the most overlooked aspect of integrating electronics into a marching program.
In this post, we will go through the key points of measurement of electric power and how to calculate the power consumption requirements for your marching audio system. Once the power requirement is found, we will then look at choosing power generators and extension cables suitable for your needs.
The Lingo
As with most complex topics, it's extremely valuable to get familiar with the building blocks of the subject. Voltage, Current, Resistance and Power are the four key elements we'll be dealing with while discussing electricity and power consumption.
Current is the actual flow of electricity through a circuit. In our case, a circuit is our marching sound system. Current is measured in Amperes, or Amps for short, and is represented with an "I" in mathematical formulas.
Resistance is how much a device or material inhibits the flow of electricity and is measured in Ohms. Resistance can be represented with either an "R" or "Ω" in mathematical formulas.
Voltage is the charge added to an electric circuit to actually produce the flow of electricity. It can be thought of as a water pump adding water pressure to a water pipe system. Voltage is measured in Volts and is represented with a "V" in mathematical formulas.
Power, or electrical power, is the rate at which electrical energy is transferred by a circuit, per unit time. In other words, it's how much work an electric circuit can produce within a given time frame. Power is measured in Watts and is represented by a "W" in mathematical formulas.
In short:
V (Voltage) is measured in Volts
I (Current) is measured in Amps
P (Power) is measured in Watts
R (Resistance) is measured in Ohms
Important Formulas
These formulas allow us to easily plug-in the power ratings of sound equipment and quickly find the measurement we're looking for. Keep these in mind as they will absolutely prove useful!
To find Power (W)
V x I = P
Voltage x Current = Power
Volts x Amps = Watts
To find Voltage (V)
I x R = V
Current x Resistance = Voltage
Amps x Ohms = Volts
To find Current (I)
V / R = I
Voltage / Resistance = Current
Volts / Ohms = Amps
To find Resistance (R)
Voltage / Current = Resistance
V / I = R
Volts / Amps = Ohms
A Note About Voltage
In pretty much every situation where a power generator is being used, 120V will be a constant value provided by the generator. This is particularly useful as we need both the Voltage measurement and Current measurement to calculate Wattage. Alternatively, we can also use Watts and Volts to calculate the total Amps in a circuit.
Now, I'd be remiss if I didn't note that 120V is the standard Voltage used in the United States. This means that, in theory, all power outlets should supply a healthy 120V, but this isn't always the case. This is also why having a power generator is so valuable in regards to marching audio systems; Not all outlets, especially outdoor outlets, supply a clean 120V. This is also a great time to mention that having a power outlet tester on hand is crucial when plugging into stadium power. Power conditioners are also great for protecting the system and ensuring clean power is being fed to the system.
An Example
In this example, we're going to calculate the power requirements of a sound system composed of two Yamaha DZR15 full-range loudspeakers and two Yamaha DXS18XLF subwoofers. We'll also be using the Yamaha TF5 mixing console and a Yamaha MODX8 as our synthesizer with a Mackie SRM150 monitor.
Here's our example gear list with their power consumption ratings:
DZR15 Qty. 2 -----------600W at 1/2 Max Power
DXS18XLF Qty. 2 ------720W at 1/2 Max Power
TF5 Qty. 1 ----------------120W
MODX8 Qty. 1 -----------16W
SRM150 Qty. 1 ----------100W
So what do we do with these numbers? We add them! Fortunately this part is fairly simple.
600W + 600W + 720W + 720W + 120W + 16W + 100W = 2876W
In our example system, the total number of Watts is 2876W. Keep in mind, though, that this number was found using the power consumption rating of the speakers at half power. This means that running the speakers closer to their max rating will use more power. However, it's at this point that we begin crossing over into the audio realm as speakers very rarely are at their max for a prolonged duration of time. Unless, of course, something has gone horribly wrong.
With our 2876W of power, we can then divide by 120V to find the total Current. Don't forget that we use 120V because it is a constant value provided by a power generator. Plugging into stadium or wall power may yield different results.
2876W / 120V = 23.96A
These measurements now allow us to look at generator and extension cable specifications to select the appropriate choices.
Choosing A Generator
Purchasing a power generator can be quite the investment. Depending on the size and needs of your particular audio system, a large generator with a very high power output might be necessary. On the other hand, if your group is just beginning to use electronics then perhaps a smaller generator would be more suitable. Either way you have to go, here are a few helpful points to consider:
Keep the projected growth of your group in mind. If the size of the ensemble is expected to grow in the coming years, it may be a good idea to go ahead and buy a generator larger than is needed in the current season.
Double check with your school district and campus to be sure that a motor generator is allowed; Some school systems do not allow these types of power sources to be used. In this case, the purchase of a battery power source may be necessary.
Plan to make room in your equipment truck for your generator and ensure that it is properly restrained during transit. There are even specialty field carts for generators to help with transport and mobility, such as the Titan Field Frames MUFFGEN.
Motor generators do require maintenance such as oil changes and, in the case of key-start generators, occasional battery changes.
Larger generators typically have longer run times as they have bigger gas tanks. Likewise, the more power a generator is being asked to produce, the more fuel it will consume.
Here is a handy chart of Yamaha generators and their specifications, but don't forget that there are other brand names on the market. Just be sure to check the specs before purchasing!
For the 2876W of power needed by the example audio system in the previous section, we may opt to use the Yamaha EF4500iSE Inverter Generator for our sound system since it has a rated output of 4000W, or 33.3A at 120V. This generator would be able to supply our system with plenty of clean power very comfortably.
Alternatively, we may also look at the Yamaha EF3000iSEB, which has a rated power output of 2800W and a maximum output rating of 3000W with the 500W boost if the sound system draws more than that 3000W max for a short duration. The EF3000iSEB may also be a good option if we don't anticipate having to crank our example system very hard by using the speakers at less than their half-power rating more often than not.
Choosing Power Extension Cables
The power cable is by far the most overlooked component of many marching audio systems. The importance of this component, however, cannot be overstated. In the same way that having great microphone cables is important to delivering a clean audio signal to your mixer, having an appropriate power extension cable is critical to delivering the required amount of power to your system in a safe manner.
Simply put, you need a cable thick enough to deliver enough power to your audio system while being long enough to reach where you want to place your generator. As a general rule of thumb for standard power extension cables, the longer the cable is the thicker the cable needs to be. Also be sure that the cable you select is able to handle high enough Amperage.
Cable length ----- Recommended Thickness
25' ----- 14AWG
50' ----- 12AWG
100' --- 10AWG
Another aspect to consider is the max Amp output your generator may offer for the type of extension cable connector. The Yamaha EF3000iSBE, for example, has two Edison outlets that only provide 120V at 20A. This means the maximum number of Watts we can pull from a single outlet is 2400W; Much less than our calculated requirement in the example system.
Luckily, there are options. These larger generators typically do have power outlets for higher Amperage. The downside is that the connector types for these outlets are much less common than the Edison connector.
Enter the L5-30 Power Connector and cable. The L5-30's are rated for 30A/125V of power; plenty for even the largest marching sound system applications. They're also designed as a twist-lock style connector for peace of mind that the cable won't be accidentally unplugged during a performance.
Given that the connector type itself is specialized, it also must be noted that a specialized power-inlet is required in your mixer cart. I recommend the Whirlwind E1 PowerPak for connecting an L5-30 cable from your generator to your mixer cart.
While the use of an L5-30 cable and PowerPak is recommended for larger systems, there's no denying that it can be a costly investment. However, do remember that this recommendation comes from the viewpoint of best practices and safety! Many smaller to mid-size systems can operate quite comfortably and safely with a standard 20A extension cable.
A Few More Tips
As power cables are such an important aspect of your marching audio system, be sure to take care of them as much as we would take care of audio cables and snakes. Power cables are often overlooked; missing ground pins, small nicks and cuts in the rubber shielding, debris in the Edison plug... All of these small details affect the overall performance of the power cable, and thus the performance of the audio system.
Cable Cuffs and cable manager buckets are great ways to keep your power cable safe during transport while increasing efficiency during setup and teardown. Just like with SpeakOn cables and snakes, having the power cable prepped before it's showtime is a great way to ensure a successful field entrance.
To Recap
You can calculate the approximate power consumption of your system by adding the manufacturer power ratings (in Watts) of all of your equipment together. Divide the total Watts by 120V to find the Amperage of the system. These numbers will help you select an appropriate power generator and extension cable.
Don't forget to maintain your power source and keep great care of your power extension cables as these components provide the necessary energy for your marching audio system to do what it's designed to do: Help your marching ensemble sound the best it can.
Lastly, please don't hesitate to reach out for assistance with any questions you may have about your system! While Microphonic Designs is not able to sell power generators, we can help ensure you select one that's going to work great with your gear. We are also happy to help you procure new pro audio equipment for your ensemble, alongside the many audio and design services we offer for marching band and indoor percussion ensembles.
Be sure to visit our Contact Page to get in touch and check out all of our services for marching band and indoor percussion. for more information about what Microphonic Designs can do for your program.
