Abstract: An acoustic power system includes a speaker which generates acoustic energy in response to electrical driving signals. Electrical representations of the acoustic energy generated by the speaker are effectively subtracted from electrical input signals having a preselected frequency response to produce electrical error signals. The error signals are amplified to produce the electrical driving signals which operate the speaker. In the preferred embodiment, the electrical representations of the acoustic energy generated by the speaker are produced by detecting a portion of the impedance produced across the speaker voice coil.