Hi KCSkins and all,
Actually, the correct term is "sensitivity," not efficiency. Relatively speaking, all loudspeakers are horribly inefficient in terms of producing acoustic watts from electical watts.
Actual speaker efficiency varies from about 0.5% to a maximum of about 10%. The most sensitive, or efficient, are huge horn-loaded systems and arrays you see used for outdoor concerts and auditoriums. These often have sensitivity ratings of greater than 100 dB/1 watt/1 meter, which means they produce extremely loud sound at a distance of 1 meter with 1 watt of input power. In these designs, fidelity and accuracy are sacrificed for sheer sensitivity, so enormous 10,000-watt amplifiers aren't required to fill an auditorium.
Most domestic hi-fi speakers that don't use horn-loading have typical sensitivities between abou 86 dB/1W/1m and 95 dB/1W/1m. There is no necessary correlation with speaker sound quality and sensitivity, except when you move into horn-loaded systems. . .
Regards,
