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Engineering LibreTexts

17.1: Theory Overview

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  • Loudspeakers are typically specified with a nominal impedance of four or eight ohms, although other values are possible. The actual impedance of a typical loudspeaker can vary widely from this rating. This exercise examines the impedance of two different permanent magnet-voice coil type transducers with respect to frequency. Both amplitude and phase are important to consider. Devices of this type normally exhibit a resonant peak in the bass end and a gradual rise in magnitude as frequency increases. The phase angle is at times capacitive, inductive, and also resistive. Typical loudspeaker impedance is not nearly as consistent as simple resistors. The resulting complex impedance can present a much more challenging load for an audio amplifier than a simple ideal eight ohm resistance.

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