Ace Quality Audio Hire/Comentech

What??? What is a watt. There’s watts all over this web site, I know its got something to do with how loud a sound system is, but please explain:-

Put your school uniforms on folks, we are going to school again. Do you have vague memories of your High School science classes? Does anyone have the fortitude to remember the physics semester? Sometimes key words are a good way to jog unpleasant memories; remember ENERGY? It’s that part of our universe that enables change to take place, or put another way, the capacity to perform some kind of work. Now, some people (not that many probably) had the stomach to sit through the explanation of the concept of POWER! What is power, think now…. no it won’t come back. POWER is ENERGY used per UNIT OF TIME.

Ahhh now we are getting warm, a WATT is a unit for measuring POWER. More specifically the measure of an amount of energy used in one second of time. Because most explantions of energy used per unit time will be longer that one second, we should really think like engineers talk about power and say energy used per second per second.

That’s great, but how do we get this in perspective with sound gear? First let’s do a table of some rule of thumb power levels expressed in watts we run across in everyday life:-

Interesting isn’t it, an amplifier pushing out 500 watts is working harder that a human sprinter running a 100 metres race. An amplifer pushing out 1000 watts is working at a rate of more than one horsepower, in fact for an example it is working about as hard as your average domestic lawn mower. I know what you are going to say now I think…. “I’ve got a reasonable concept of what its like to run flat out for a 100 metres, and I know what happens to a toe caught in a lawn mower blade, if that same power was sound energy shouldn’t it be incredibly loud?” Your’e darn right it would be!

Sorry, back to our High School physics class for this last bit. If we were able to sit through energy, stay awake for power, you were almost certanly nodding off, if not asleep for THERMODYNAMICS. The teacher, bless his/her little cotton socks would have spouted on about the LAWS OF THERMODYNAMICS. There’s three of them if you really really want to know.

It’s the second one that we are interested in here. It says in my humble translation “any process in which energy is converted from one form to another is not 100% efficient, some energy is always lost as heat”. Hmmm… perhaps a little glimer of light here? Our sound system is plugged into a power point and takes in energy in the form of electricity, after many operations sound energy comes out of the speakers. What is going to happen in our 500 watt amplifier, all along the chain of events energy is leaking away as heat. The power cord gets a little warm, the amplifier and all the gizmos attached to it definitely heats up, the leads carrying power to the speakers get warm and finally the voice coils in the speakers heat up. So, our work rate of 500 watts at the power point has partly ended up as sound, and partly as waste heat! Now wait for it…. you average speaker with a paper cone is only a few percent efficient! A horn speaker is more efficient, around 20 percent.

If we get 25% of the power in coming out as sound we are doing real well, in fact we are using top quality audio gear. So, our 500 watt amplifier may give off at the end of the day less than a 100 watts of sound power. You do not by any means, hear coming out as sound all the power that goes in!

There’s more coming very soon!!!