LPM – Linear Parameter Measurement

LPM The Klippel LPM software module allows you to quickly acquire traditional small signal (Thiele-Small) parameters as well as measure suspension creep and lossy inductance of electrodynamic transducers. The inductance model is user selectable (LR-2, LEACH and Wright).

LPM generates a multi-tone stimulus while simultaneously using a laser displacement sensor to track the diaphragm motion. The stimulus and motion data are automatically correlated and LPM generates the Thiele-Small parameters, suspension creep and lossy inductance within seconds of starting the measurement.

LPM Displacement Transfer Function

Displacement Transfer Function (click for larger image)

Klippel LPM Impedance magnitude

LPM Impedance magnitude (click for larger image)

LPM continuously monitors the nonlinear distortion to ensure the transducer is operating in its linear region and provides feedback to the operator if not. Adjustments to the measurement setup will correct for this.

The LPM module also supports the traditional 2 step perturbation techniques (added mass or added test box volume). These methods can be used to cross check the single step laser technique if desired.

LPM shows an overlay of the measured impedance curve and the modeled impedance curve to highlight the differences. A curve fitting error numerical value is also indicated. This is how you would sanity check the results.

Here is an example of the LPM test results from a typical woofer.

LPM Woofer parameters report

LPM Woofer sample report

For further information, you can check out Klippel’s official website.

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