Few subjects generate more confusion in the audio world than power.
There is a very good reason for this - it’s a confusing subject, and one that can easily fool our intuition.
Most of us are on a power trip - our attitude is that “more is better.” We want bigger amplifiers and more “powerful” loudspeakers so that our sound systems will be louder.
In fact, power ratings are often the main (or only) criteria considered regarding amplifiers and loudspeakers by equipment buyers. But here, let’s take a bigger look at the role of power in sound systems, hopefully without diminishing or overemphasizing its importance.
Power ratings are only one piece of a larger puzzle. Trying to characterize amplifiers or loudspeakers only by power ratings is akin to trying to completely characterize a person by a photograph.
There is always much more than meets the eye.
To form our understanding about power, let’s initially forget about sound systems (with the exception of an occasional reference) and consider power in light of other ways that we use it in daily life.
We will begin with some basics. Power is both generated and consumed. From the perspective of generation - more is better. We always want to have more power available than what we need.
From the perspective of consumption - less is better. If a task can be accomplished using less power, we save money since power generation usually costs money.
Power is wasted if it is not doing something useful. In sound systems, amplifiers and loudspeakers are both consumers and generators of power.
The amplifier consumes power from the electrical service and generates power to drive the loudspeaker. The loudspeaker consumes power from the amplifier and generates sound power into the room.
Rating methods are used to describe both power generation and consumption (both are in watts). Great care must be taken to be sure which one a power rating is describing, since a larger rating may be better for a power generator, but a smaller rating may be better for a power consumer.
Universal Principles
No, this isn’t a self-help infomercial – it’s a discussion of some of the properties that affect the flow of power. Power principles are analogous in electrical and mechanical systems.
Mechanical examples are more prevalent in our everyday lives, so it is easier to look at power from that vantage point.
We begin with energy. In fact, everything began with energy. Energy sources include power plants, automobiles, locomotives, bombs, animals and humans, and less-obvious sources such as plants, water, wind and even garbage.
All energy sources must get their energy from somewhere else, making the “big picture” question a religious one (we won’t go there). Most of the energy on planet Earth comes from the sun - the ultimate power source in our physical sphere of existence.
Let’s get the terminology in place. Energy is measured in joules. It can just sit captive (potential energy) or it can be put into motion (kinetic energy), be it water turning a turbine or a husband taking out the trash.
Work is the result of using a force to move something over a distance, so work is equal to force times distance. Power is the rate of doing work.
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So, for power to be generated, work must be done for a period of time. If the time span is reduced, so is the generated power. Remember that when you look at specs such as “instantaneous peak power.”
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That’s an important point, and we will come back to it. Power can be rated in watts, with one watt being equal to one joule per second.
You As Power Generator
A good way to get a better feel for power generation and consumption is to consider a generator that we all possess - our bodies.
We humans consume energy in the form of food, store energy in the form of fat, and then burn it up in the course of day-to-day living. We convert energy from one form to another.
An in-depth yet easy-to-understand discussion of wireless systems, how they operate, issues that can plague performance, and solutions that do the trick in the vast majority of situations.
