SpeaD 1.0 · Impedance

Impedance

The predicted electrical impedance of the driver at rest, from two voice-coil inductance models — cold and at power.

Predicted |Z| from the design

The Impedance page plots |Z| from 10 Hz to 20 kHz with the coil at rest, built from the design: Re, a voice-coil inductance model, and the motional branch from fs, Qms and BL. It is recomputed every time you open the page.

SpeaD Impedance page for the Standard start design with LR-2 and LR-4 curves — The Impedance page for the Standard start design, with the LR-2 and LR-4 curves.

Two inductance models

LR-2 — the classic two-inductor model: series Re and Le plus L2 shunted by R2, standing for the eddy currents in the motor iron. L2 and R2 are the parameters printed on Klippel-style data sheets.
LR-4 — a semi-inductance model that follows the square-root-of-frequency rise of a voice coil on a solid iron pole across the band.

After a Power Handling run, at power curves raise the series Re by the run’s hot / cold ratio, lifting the curve and damping the resonance peak. The Model parameters block lists the values behind every curve.

SpeaD Impedance page with LR-4 cold and LR-4 at power curves — LR-4 cold and LR-4 at power, with the Power Handling run it came from.

Read the Impedance chapter of the SpeaD Owner’s Manual for every control on the page.