• Technology
• + Voice Coil Impedance
• Introduction
• Glossary
• Lumped Impedance Modelling
• Measurement
• Fem Modelling
• Prediction of Distortion
• Conclusion
• Download as PDF
• + Surround Sound with Fewer Speakers
• Introduction
• Sound Quality Objectivies
• Creating Virtual Soundfields
• Practical systems
• Conclusion
• Download as PDF
• + Optimum Diapragm Waveguide Geometry
• Introduction
• Sperical Waves
• Analysis Stategy
• Results
• Discussion
• Conclusion
• Download as PDF
•   Pod Technology
• + Uni-Q White Paper
• Introduction
• Background
• Co-Axial Drivers
• Co-Incident Drivers
• Magnetic Design
• Acoustics
• Discussion
• Conclusion
• References
• Full Paper (PDF)
• + High End Uni-Q
• Coincident Source Array
• Finite Element Analysis
• Dome Profile
• Wavefront Analysis
• Motor Systems
• Laser Vibrometry
• References
• + Reference Paper
• Introduction
• Research & Development
• Reference 207
• Production
• System Design
• Boundary Control Device
• + ACE Technology
• Introduction
• How Does ACE Work?
• Adsorption
• Improvements
• Performance
• Applications
• Technology
• References
• Full Paper (PDF)

Conclusion

Detailed knowledge of the voice coil inductive behaviour is essential for the design of loudspeakers with minimal distortion.

In this paper, the variation of voice coil impedance with position and frequency has been both measured, using a new quasi static technique discussed in section 3, and modelled, using static transient FEM, with exceptional agreement. It is possible to use this information to investigate the effect of the shorting rings and to derive other indications for improvements.

The measured voice coil impedance may be expressed in terms of just a few meaningful parameters using Wright, Leach or LR-2 models. The LR-2 model allows the expression of the variation with displacement in a form that may be incorporated into electrical circuits or digital systems. Extended models, with more RL cascades, may also be used in the same way. Loudspeaker 2 impedance results show that all LR-2 parameters must vary independently with position to satisfactorily describe the non-linear behaviour of some loudspeakers over the full frequency range.

A non-linear lumped parameter model using the new LR-2 model has been successfully used to predict the intermodulation distortion of a loudspeaker. Calculation of the loudspeaker response to a complex signal using dynamic transient FEM proved to be impractical due to long solution times. However only the FEM modelling shows the influence of geometry and materials. These may be considered by expressing the stationary transient FEM results in terms of the LR- 2 parameters.

Where the lumped parameters are known, either from FEM or measurement, we can predict the behaviour of the loudspeaker for any input signal. Both linear and non-linear components may be included in the model. Any individual component (motor, supension & acoustics) of the model may be considered and reevaluated without the need to recalculate unchanged parameters. The ordinary differential equations can be solved on a PC in a few seconds or with DSP in real time for any input signal. This allows either figures of merit, such as intermodulation distortion, to be evaluated or direct evaluation by auralization of a music signal.

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