Electrodynamic Transducer Analysis through Electronic Analogies

Abstract

The objective of this project was to gain experience in analyzing and working with loudspeakers. The first step of this process was to learn how the electrical model for the loudspeaker is set up. This model predicts the electrical qualities that a loudspeaker will possess. The motion of the loudspeaker cone changes the speaker's electrical characteristics. This is intuitively obvious because the moving cone is storing and dissipating energy, which must change it's electrical qualities as presented to an amplifier or other device connected to the loud speaker. The second part of this project was to determine at various frequencies the component of the loudspeaker's impedance which is caused purely by the cone's motion. Analysis of this "motional impedance locus" yields the electrical and, through our analogy, mechanical characteristics of the speaker. Next a frequency response curve is recorded for the speaker mounted in an "infinite baffle". By deriving a complete electronic analogy of the loudspeaker, and substituting the previously calculated values into this circuit, the frequency response of the speaker can be predicted and compared with the measured response.