When you're ready to buy your next stereo amplifier or receiver, make sure you consider the amplifier's power output, which is measured in watts per channel. Deciding how much power you need should be based on the types of speakers you have, the size of your room and acoustic characteristics, and the planned loudness and desired quality of your music.
How Much Power Do Your Speakers Need? | Crutchfield
Make sure that the power requirements of the speakers match the output power of the amplifier or receiver. The power should be equal to the impedance value for each of the speakers. Some speakers require more or less power than others.
A speaker's sensitivity is expressed in decibels, which is a measure of how much sound can be produced with a given amount of amplifier power. For example, a speaker with low sensitivity (88 to 93 dB) will typically require more amplifier power than a speaker with higher sensitivity (94 to 100 dB or more) to play and sound optimally at the same volume level.
Power and speaker volume follow a logarithmic, not linear, relationship. For example, an amplifier with 100 watts per channel will not play twice as loud as an amplifier with 50 watts per channel using the same speakers. In such a situation, the difference in maximum loudness is slightly louder; the change is only 3 dB.
