Amplifier power is a misunderstood concept. Many people confuse the power or wattage of a speaker amplifier with its loudness. Doubling the output power of a speaker does not double the maximum volume of the speaker. There are two ways in which amplifier power is relevant: the efficiency of a speaker and the ability of the amplifier to handle volume peaks.
BS Speaker Sensitivity Ratings and "Dynamics"
Loudspeaker efficiency, also known as speaker sensitivity, is a measure of the decibel output of a loudspeaker for a given amount of amplifier power. For example, the efficiency of a loudspeaker is usually measured using a microphone placed one meter away from the loudspeaker. When one watt of power is delivered to the loudspeaker, the microphone measures the resulting volume using a decibel level meter. The resulting output level is the efficiency rating of the loudspeaker.
Loudspeakers range in efficiency or sensitivity from about 85 dB (very inefficient) to 105 dB (very efficient). For comparison, a speaker with an efficiency of 85 dB requires twice as much amplifier power to reach the same volume as a speaker with an efficiency of 88 dB. Likewise, a speaker with an efficiency of 88 dB requires ten times as much power as a speaker with an efficiency of 98 dB to play at the same volume.
If you start with a 100 watt/channel receiver, you will need 1000 watts of power to double the perceived volume.
