Power Amplifiers

The signal that comes out of the mixer is barely strong enough to power your headphones, so you need something which will amplify this signal, enabling it to drive a pair of speakers. There are three choices on how to do this: 1) Buy a separate amplifier and speakers. This can be a bit costly, but it is a great way of doing it. 2) Using POWERED or ACTIVE speakers. These are speakers with a built in amplifier, so you plug them into a power source and connect a mixer directly into them. 3) Plug the output cable into either the CD or AUX port in the back of your stereo (if you have one).

There are many variables that can go into choosing the right amplifier to match with a loudspeaker. Some of the most important information to know first is what the continuous power rating of your loudspeaker is, and what its nominal impedance is. A good rule of thumb is to select an amplifier that can deliver 100%-200% of the loudspeaker’s continuous power rating at its nominal impedance. As an example, a speaker is rated at 400W, continuous and has an 8-ohm nominal impedance. One amplifier is rated at 400W into an 8-ohm load and another amplifier is rated at 550W into an 8-ohm load, so either of these models would be good choices for a 400W speaker. The wattage output of an amplifier tells you how much power it can put into the loudspeaker. Although, in general, a more powerful amplifier will play louder quite a bit is dependant on the loudspeaker. The power output of an amplifier does not necessarily equate to the quality of its sound.

Can the speaker wattage be less than the amplifier/receiver wattage?
In short, yes. However, if the speaker is rated lower than the output of the amplifier or receiver you run the risk of overdriving the loudspeaker. Overdriving a loudspeaker can damage it. Normally you want to choose a loudspeaker with the same or higher max rated power (Watts) than the amplifier you will drive them with. Most loudspeakers have two power ratings: maximum continuous power and peak power. The continuous power tells you how much power the loudspeaker can handle “all the time” and peak tells you how much power the loudspeaker can handle for short periods.