Many people have their understanding of amps and speakers all backwards. The way it really happens is that the speaker puts a load on the amp. When you think of matching up speaker and amp, you can use the “trailer and car engine” scenario. Picture this… If you have a trailer loaded down with heavy cargo and try to pull it up a mountain with a car, you can easily see how the trailer makes the engine work harder than normal. The same thing happens with an amp. The speaker, (or load) makes the amp, (or engine) do the work. This load in speakers is measured in ohms. Each speaker has an ohm rating that never changes. The lower the ohm number, the greater the load. Thus a 16 ohm speaker doesn’t require much work out of the amp. On the other hand, a 4 or 2 ohm speaker really makes the amp work hard. If you pair two 16 ohm speakers together in parallel they will double the load to 8 ohms. Two 8’s would make 4 and so on. Obviously adding more speakers will increase the load just as adding more trailers to the car would increase its load.
Wattage can almost be thought of as horsepower. Just like the car engine, the greater the wattage rating of the amp the more power it has. When an amp is not under much load, it does not use very much of its wattage. If the amps volume is at 10% then the wattage output is never greater than 10%. The only way to bring an amp to full wattage is to have its volume set at 100% and to have its input signal cranked up to 100% also. If you lower the input signal to 50% then the wattage will drop proportionally even though the output volume is still at 100%.
Speakers have a wattage rating too but they rarely, if ever, see that much. It means that if you exceed their rated wattage for any length of time they would probably get too hot and burn out. They can take high spikes in wattage for short periods of time because it takes a little time for the heat to build up. Most modern speakers have some sort of cooling system built in. An extreme spike in wattage, (say a snare hit), may only last for a fraction of a second. A few now and then won’t hurt most speakers because they can cool themselves and recover from the spike. The amount they can handle safely is referred to as their “peak rating.” If the spikes in high wattage become more frequent they can begin to build up more heat than the speaker can recover from. The safe level rating of frequent peaks is called “program rating.” Some engineers arrive at the safe program level mathematically. They use a formula that finds “root-mean-square” or RMS. It pretty much just means an average number of peaks mixed with an average number of valleys in the signal, blah, blah, blah. The program or RMS is the rating that you should be concerned with and stay within. Of course the only way to really know for sure is to put a wattage meter between the amp and speaker. Most people don’t use wattage meters. Instead they just don’t ever run their amp inputs at full power. An easy way to judge where the danger zone begins is the point at which the output signal begins to distort or sound fuzzy, crackled, or unnatural.
As long as you keep the volume under control, it is perfectly safe to have an amp that is rated much higher than the speaker. In fact, it is recommended. Just as an engine with lots of horsepower is good for pulling trailers up hill, so too is lots of wattage. Many engineers use amps rated at double or even triple the rating of their speakers.
Hope this helps. Sorry for writing a book here but hey, learning is good.
Gordon
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