Reinventing physics - loudspeakers and efficiency
It never ceases to amaze me how much half-knowledge is contained in the information on various products. Today, for example, the efficiency of loudspeakers. You read everywhere about loudspeakers: Efficiency: xy dB Ehm ok... very good loudspeakers have an SPL/Lp (Sound Pressure Level) or (characteristic) sound pressure level of over 100 dB, and when efficiency values of over 100 are stated and then labelled with a unit, the alarm bells should actually ring. Efficiency - Is always unitless - Can never be over 1 or over 100% never, never, never and never again (perpetuum mobile!) - Is a ratio of the output power to the input power - Is specified with the factor 0-1 or in per cent 0-100%. What you call efficiency is actually the (characteristic) sound pressure level and nothing else. The sound pressure level (dB) is in turn a ratio (logarithmic) of the measured sound pressure p (Pa) at a distance of 1m to the reference value (hearing threshold of the human ear) of 20uPa, at 1 watt input power with a frequency of 1kHz, to put it simply. The often stated 2.83V (rounded) only refers to 8 Ohm speakers (1W input power), with 4 Ohm speakers it is 2V (exact) U = root(P/R) The topic and the reference measurement for loudspeakers is even more complex, for those interested there are search engines ;-). A loudspeaker with an SPL of 109dB (Klipsch - The Fives, for example) has an efficiency of around 50% (which is already absolutely top), a loudspeaker with an SPL of 92dB has an efficiency of just 1%. It would be nice if you could simply state SPL instead of efficiency, or sound pressure level. Unfortunately, many loudspeaker manufacturers also give this information (efficiency = xy dB or dB/W/1m), which is simply not correct.
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