Efficiency and power rating of loudspeakers

The specification of the performance of loudspeakers is a subject of international controversy at the present time. Several groups in this country are concerned with standardized methods of evaluating the performance of loudspeakers in order to have a basis for comparison. Several European countries are also concerned with similar problems. The measurement of the response-frequency characteristic and directional characteristics of loudspeakers is routinely performed by various laboratories. Sufficient agreement can be attained by the various laboratories to standardize this measure of performance. It is important to have a measure of the efficiency, that is sound power output vs electrical power input, and also a method of specifying the power handling capacity of a loudspeaker. Various methods are in use at the present time to indicate the characteristics of a loudspeaker concerning these two measures. The method of using a reverberation chamber to integrate acoustic power output and thus determine the efficiency will be discussed in comparison to the more tedious method of analytical integration of measurements performed in free space. Power handling capabilities of loudspeakers as determined by distortion measurements and mechanical or electrical failure will also be discussed. A summary of the various methods of specifying both efficiency and power handling capacity as used in various laboratories in both the United States and Europe will be included.