Loudspeakers

Loudspeaker efficiency is notoriously low, typically <1%, but measuring efficiency as 'electrical power in/acoustic power out' is complex, involving integrating the output over a full 360° in both vertical and horizontal planes. As a result, this is more typically expressed by speaker sensitivity – the SPL realised at 1m distance from an input of 2.83V (equivalent to 1W/8ohm). Of course, applying 2.83V across a '4ohm' speaker is equivalent to 2W, so one brand's 1W/1m spec. is not equivalent to another's at 2.83V/1m. Frequency, too, is vital. Measured at just 1kHz, 'sensitivity' is at the mercy of a peak or dip, which is why we also publish an RMS value across 500Hz-8kHz. How loud your speaker sounds will depend on both response and level, as defined by the ISO 226 'equal loudness contours'. PM