Make sure to factor for amplifier output power when you’re ready to purchase your next stereo amplifier or receiver. Power is measured in watts per channel, and the decision about how much power you’ll need should be based on criteria including:
- The types of speakers that you intend to use
- The size and acoustic characteristics of the room
- The planned loudness and desired quality of your music
Match Your Power Requirements
Match the power requirements of speakers with the output power of the amplifier or receiver. Power should equal the impedance rating for each of the speakers. Speakers require more or less power than others — loudspeaker sensitivity is expressed in decibels, which is a measure of how much sound output is produced with a specified amount of amplifier power. For example, a speaker with a lower sensitivity (say, 88 to 93 dB) tends to require more amplifier power than a speaker with a higher sensitivity (94 to 100 dB or more) in order to play and sound optimally at the same volume level.
Power and Volume
Power output and speaker volume follow a logarithmic, not linear, relationship. For example, an amplifier with 100 W per channel will not play twice as loud as an amplifier with 50 W per channel using the same speakers. In such a situation, the actual difference in maximum loudness would be just slightly louder; the change is only 3 dB. It takes an increase of 10 dB in order to make speakers play twice as loud as before (a 1 dB increase would barely be discernible). More amplifier power allows the system to handle musical peaks with greater ease and less strain, which results in better overall sound clarity.
Some speakers must work a little harder than others to achieve a specific volume output. Certain speaker designs are more effective than others in projecting sound evenly across open spaces. If your listening room is small or carries audio well, you may not necessarily need a super-powerful amplifier, especially with speakers that are more sensitive to power. But bigger rooms or greater listening distances or less sensitive speakers will certainly demand a lot more power from the source.