In general, efficiency is defined as desired output divided by required input. In the case of speakers, the desird output is acoustic power (sound) and the required input is electrical power (from the amplifier). So speaker efficiency is defined as acoustic power out of the speaker divided by the electrical power into the speaker.

A typical speaker has an efficiency of about 1%. So for 100 watts of electrical power into the speaker, it is putting out 1 acoustic watt. 1 acoustic watt does not sound like much, but in a typical home environment, is is quite loud.

As I said, the speaker puts out acoustic power. Speaker specifictions usually give specs on sensitivity, efficiency, or whatever term they use, as XY dB with 1 watt of input power (electrical) at, typically, 1 meter (and, technically, an acoustic environment should be specified, such as an anechoic chamber, "typical" living room, or whatever, but often the environment is not specified).

One needs to know the acoustic environment in order to translate from acoustic power (watts) to sound intensity level (dB).

My electrostatic speakers are probably on the order of 1/2% efficeint. Large horn type speakers can be vastly more efficent. I have read that large Klipsch corner horns are about 40% efficent. The horn acts sort of like an mechanical-acoustic transformer, matching the mechanical impedance of the moving driver cone, dome or whatever to the mechanical impedance presented by the air the speaker is trying to move (vibrate).

Paul


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the 1derful1