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2 speakers are playing at same volume from computer. One speaker volume is controlled by software but knob turned to maximum. Another speaker has volume knob set at 75%. Both are playing at same volume. Which method of controlling speaker volume consumes more power?

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  • \$\begingroup\$ Why would you care about the power consumption of the volume control circuit? It'd be more relevant to speculate which speaker was taking more power. This question seems irrelevant and is unanswerable without guesswork. \$\endgroup\$ – Andy aka Mar 18 '16 at 8:59
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I am assuming you mean that the speakers have built-in audio amplifiers.

The power consumed by the audio will depend on the volume of the loudspeakers. If both amplifiers are playing at the same volume they'll both consume the same power.

schematic

simulate this circuit – Schematic created using CircuitLab

The power dissipated in a 10 kΩ pot with a 1 V line-level signal would be given by \$ P = \frac {V^2}{R} = \frac {1*2}{10k} = 0.1~mW \$. Maybe you could save 0.25 mW by turning the pot up to max and turning the volume down in the computer. Compared with the several watts require for the amplifier it's negligible.

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