How much power of speaker amplifier do I need?

"How much power should the power amplifier need?"  Many people think that bigger is better. But there are actually many considerations. On the one hand, power amplifiers with higher output power are bigger, more expensive and consume more power; secondly, do you really need such a high-power power amplifier? Does more power mean better sound quality?

The factors involved include the listening environment, the distance between the speaker and the listener, the efficiency of the speaker, and the power it can withstand, etc., which will affect the power requirements of the audio system for the power amplifier.

Now, we mainly explain "the efficiency of speaker'', it is the sound pressure obtained by inputting a 1W signal at a distance of 1 meter from the front of the speaker, which is the axis of the sound. 

The efficiency of each speaker is different. 

Generally speaking, the efficiency of the speaker is usual in the range of 82-88dB/w/m (dB = decibel). If the nominal efficiency is 86dB/w/m as an example, it means the speaker is at a distance of 1 meter from the sounding axis line (that is, directly in front of the speaker's front baffle), and the sound pressure will be 86dB when a 1W (watt) signal is input. 

However, the sound pressure is inversely proportional to the square of the distance from the sound source, so if the general listening distance is estimated at 2 meters, the same speaker will only have 80dB sound pressure when the input power is 1W (the algorithm of dB is doubled every 3dB, and the distance is doubled. 1/4 sound pressure is -6dB).

So to be able to achieve the basic sound pressure of about 90dB for general listening, we need about 8W of power to have a sound pressure of 89dB. Therefore, if the speaker efficiency is not too low, generally speaking, a 10W power amplifier can listen to music normally without any problem.