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Large Signal Identification (LSI)

Large Signal Identification

  • Direct identification of transducer nonlinearities
  • Electrical, mechanical and thermal parameters
  • State variables (displacement, temperature,…)
  • Measures signal distortion on-line
  • Full thermal and mechanical driver protection
  • Finds dominant sources of distortion
  • Locates weak points in design and assembly

LSI modules measures the linear, nonlinear and thermal parameters of transducers operated in free air or in a sealed or vented enclosure. The transducer is operated  under normal working conditions (vertical position and fixed clamped in a laser stand or enclosure). Starting in the small-signal domain the amplitude is gradually increased up to limits admissible for the particular transducer. The maximal amplitude is determined automatically using the identified transducer parameters and general protection parameters describing the thermal and mechanical load.  The identification of the model parameters is performed in real time with an adaptive system. It is based on the estimation of the back EMF from the voltage U(t) and current signal I(t) measured at the electrical terminals. The identified model allows locating the sources of the nonlinear distortion and their contribution to the radiated sound. The dynamic generation of a DC-part in the displacement, amplitude compression and other nonlinear effects can be investigated in detail. After the initial identification a temporal parameter variation and long-term thermal effects can be investigated. The data is stored in the stand-alone processor unit and can be transformed via the USB interface to a connected computer for visualization and interpretation.

Specification

Products

LSI Woofer
is dedicated to low frequency drivers (fs < 400 Hz) such as woofers, headphone drivers, shakers and other electro-dynamical transducers where the mechanical-acoustical part can be modeled by a 2nd-order system (moving mass, compliance, damping). LSI Woofer substitutes the previous version LSI Pro providing various new features.


LSI Tweeter

is dedicated to tweeters, horn compression drivers and micro-loudspeakers for telecommunication which may be modeled by a 2nd-order mechanical system and a resonance frequency between 100 Hz and 4 kHz. 


LSI Box

provides the full functionality of LSI Woofer but can also be applied to woofers and other electro-dynamical transducers (fs < 400 Hz) coupled to an additional mechanical or acoustical resonator (vented enclosure, horn, panel) giving a total mechanical-acoustical system of 2nd or 4th-order. There are three working modes available: free air, sealed enclosure,  vented enclosure.

Standard

IEC Standard IEC62458 Sound System Equipment – Electroacoustic Transducers - Measurement of Large Signal Parameters

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Know-How Poster: "Loudspeaker Nonlinearities. Causes, Parameters, Symptoms"

Paper: “Loudspeaker Nonlinearities. Causes, Parameters, Symptoms”

Paper: “Assessing the Large Signal Performance of Loudspeakers”

Paper: “Large Signal Performance of Tweeters”

Paper: “Measurement of Large Signal Parameters”

Application Note AN1: “Optimal Voice Coil Rest Position”

Application Note AN2: “Separating Spider and Surround”

Application Note AN3: “Adjusting the Mechanical Suspension”

Application Note AN5: “Displacement Limits due to Driver Nonlinearities”

Application Note AN21: “Reduce Distortion by Shifting Voice Coil”

Application Note AN24: “Measuring Telecommunication Drivers”


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