Loudspeakers waste most amplifier power because sound conversion is highly inefficient

Evidence

Why should you buy a 600-watt (W) amplifier for your loudspeakers if a full orchestra normally produces just a watt of power, 40 or 50 W at the loudest? The answer is that to reproduce sound, rather large forces must be exerted on the speaker cone to get it to vibrate in a prescribed way. The conversion efficiency from motion of a loudspeaker cone to sound is very low. The cones are moved with electric currents in coils near magnets, wasting considerable energy. Imagine all the effort you would expend waving your hands back and forth 1000 times. Only a tiny fraction of that energy would go into pushing air around; most of the energy expended would go into working against yourself, so to speak: internal friction, stopping your arms with one set of muscles after starting them swinging with another, working against gravity, and so on. So it is with a loudspeaker. For that matter, musicians can work up a sweat playing an instrument, all to produce well under a tenth of a watt of sound. — Eric J. Heller, Why You Hear What You Hear- An…, 56

Categorization

• CANDY: The fact that a full orchestra makes only about one watt of sound makes for a great party-line fact.