Linear Parameter Measurement (LPM)
Features and Benefits
- Identifies linear transducer model (Thiele / Small parameters)
- Measures suspension creep
- Single-step measurement with laser sensor
- Two-step measurement with additional mass or test enclosure
- Monitors signal to noise + distortion ratio (SNR+D) and noise floor
- Automatic validity check
- High reliability and reproducibility
- Fast measurement
The LPM module of the KLIPPEL Analyzer System is dedicated to identifying the electrical and mechanical small signal (Thiele/Small) parameters of electro-dynamical transducers with high accuracy. It is based on the electrical impedance by measuring the voltage and current at the speaker terminals. Enhanced by an optional laser displacement sensor, the identification does not require a second measurement and thus avoids common problems of the traditional two-step methods (e.g. added mass). An additional benefit of the displacement measurement is the identification the suspension creep parameters, resulting in better accuracy of the loudspeaker model at low frequencies. The LPM provides tools to identify and avoid typi-cal problems such as poor signal to noise ratio and malfunction due to nonlinear effects of the driver or amplifier limiting.
Added Mass Perturbation Technique
A second measurement is performed while a known mass Madd is added to the cone.
Mms is measured primarily
Cannot be applied to tweeter and microspeakers
Mechanical resistance or stiffness are assumed as frequency independent para
Test Box Perturbation Technique
A second measurement is performed while a known air stiffness Kair is added to the suspension.
Cms is measured primarily
Depends highly on precise value of effective radiation area Sd
Residual air volume (inside the transducer) cannot be considered
Requires sealed diaphragm
Cannot be used to measure mechanical mass without air load
In addition to the voltage and current also the voice coil vibration (e.g. displacement) is measured by using an optical sensor.
Fast (one step technique)
Simple to use
BI is measured primarily
Most precise results
Can be applied to most transducers
Optical problems (angle, surface)
Coil displacement is not axial-symmetrical