The manufacturer's specifications actually DO come from industry standards. Loudspeakers are measured at their centers (physical height/2 and physical width/2) from a distance of one meter. A voltage is delivered to the speaker (using white noise, 20 to 20K Hz. if I remember right) equivalent to one watt. The actual voltage necessary for one watt varies with the speaker impedance due to Ohm's law. The calibrated SPL meter averages the decibel count at one watt / one meter, and that number becomes the published efficiency of the speaker. These measurements are taken in an anechoic chamber and are devoid of room reinforcement.

Common speaker outputs range from 80 dB (highly inefficient speakers) to 104 dB (Klipschorn). The rest (outputs at different distances and outputs at different wattages) are just plain physics.

Last edited by Boomzilla; 12/28/15 02:48 AM.
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