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6. Conclusion

A new coupled model for the numerical calculation of electrodynamic loudspeakers has been introduced. The simulation of acoustic, mechanical and magnetic systems including their couplings by using a Finite-Element-Method allows the computation of the dynamic behavior of such moving coil drivers. The validity of the simulation model has been verified with the help of appropriate measurements. The calculated and measured values for eigenfrequencies, axial pressure responses and electrical input impedances are in good agreement. Furthermore, the dependency of the behavior of the electrodynamic loudspeaker on some design parameters was investigated and significant improvements could be obtained. Response dips at intermediate frequencies have been eliminated by using modified surrounds, whereas for higher frequencies an improvement in efficiency could be achieved by placing an additional metallic cylinder in the magnet gap.

The presented computer simulations have been proven as an useful tool in the development of magnetomechanical transducers and reconfirm the value of computer-aided-design of electrodynamic loudspeakers. A complete CAE-tool for the computer-aided-design of electrodynamic loudspeakers will be established in the near future on the basis of the existing software.

The authors are grateful to Dipl.-Ing. Roland Exler of the Department of Electrical Measurement Technology, University of Linz, for his support with sound pressure measurements and Prof. Dr. Bernhard R. Tittmann of Pennsylvania State University, USA, for his useful comments on the manuscript and for the interesting discussions.

REFERENCES

[1]
H. Landes, R. Lerch, M. Kaltenbacher, CAPA User Manual, Vol. 3.1, 1998, University of Linz, Altenberger Str. 69, A-4040 Linz.

[2]
M. Kaltenbacher, H. Landes, R. Lerch, An Efficient Calculation Scheme for the Numerical Simulation of Coupled Magnetomechanical Systems, IEEE Trans. on Magnetics, Vol. 33, No. 2, March 1997, 1646-1649.

[3]
K.-J. Bathe, Finite Element Procedures, Prentice-Hall, New Jersey, 1996.

[4]
R. Lerch, M. Kaltenbacher, H. Landes, F. Lindinger, Computerunterstützte Entwicklung elektromechanischer Transducer, e&i ÖVE-Verbandszeits chrift, Vol.7/8, 1996, 532-546.

[5]
H. A. C. Tilmanns, Equivalent circuit representation of electromechanical transducers: I. Lumped-parameter systems, Journal of Micromechanics and Microengineering, Vol. 6, 1996, 157-176.

[6]
D. J. Murphy, Axisymmetric model of a moving-coil loudspeaker, Journal of Audio Engineering Society, Vol. 41, 1993, 679-690.

[7]
W. M. Leach, Jr. , A two-port analogous circuit and SPICE model for Salmon's family of acoustic horns, Journal of the Acoustical Society of America, Vol. 99, 1996, 1459-1464.

[8]
W. M. Leach, Jr. , Computer-Aided Electroacoustic Design with SPICE, Journal of Audio Engineering Society, Vol. 39, 1991, 551-563.

[9]
M. Colloms, High Performance Loudspeakers, John Wiley & Sons, Ch ichester, New York, 1997.

[10]
M. Kaltenbacher, M. Rausch, H. Landes, R. Lerch, Numerical Modelling of Electrodynamic Loudspeakers, 8th International IGTE Symposium on Numerical Field Calculation in Electrical Engineering and International TEAM-Workshop, Graz, Austria, 21.-24.September 1998.

[11]
G. S. Kino, Acoustic Waves: Device, Imaging, and Analog Signal Processing., Prentice-Hall, Englewood Cliffs, 1987

[12]
L. Michalowsky, Magnettechnik - Grundlagen und Anwendung, Fachbuchverlag, Leipzig, 1993.

[13]
M. Zollner, E. Zwicker, Elektroakustik, Springer, New York, 1993

[14]
I. Veit, Technische Akustik: Grundlagen d. physikal., physiolog. u. Elektroakustik, Vogel, Würzburg, 1988.

[15]
A. R. Selfridge, Approximate Material Properties in Isotropic Materials, IEEE Trans. Sonics Ultrason., SU-32 vol.3, 1985, 381-394

Up: No Title Previous: 5.2 Improvement in efficiency

Martin Rausch
1999-04-08

[1]	H. Landes, R. Lerch, M. Kaltenbacher, CAPA User Manual, Vol. 3.1, 1998, University of Linz, Altenberger Str. 69, A-4040 Linz.
[2]	M. Kaltenbacher, H. Landes, R. Lerch, An Efficient Calculation Scheme for the Numerical Simulation of Coupled Magnetomechanical Systems, IEEE Trans. on Magnetics, Vol. 33, No. 2, March 1997, 1646-1649.
[3]	K.-J. Bathe, Finite Element Procedures, Prentice-Hall, New Jersey, 1996.
[4]	R. Lerch, M. Kaltenbacher, H. Landes, F. Lindinger, Computerunterstützte Entwicklung elektromechanischer Transducer, e&i ÖVE-Verbandszeits chrift, Vol.7/8, 1996, 532-546.
[5]	H. A. C. Tilmanns, Equivalent circuit representation of electromechanical transducers: I. Lumped-parameter systems, Journal of Micromechanics and Microengineering, Vol. 6, 1996, 157-176.
[6]	D. J. Murphy, Axisymmetric model of a moving-coil loudspeaker, Journal of Audio Engineering Society, Vol. 41, 1993, 679-690.
[7]	W. M. Leach, Jr. , A two-port analogous circuit and SPICE model for Salmon's family of acoustic horns, Journal of the Acoustical Society of America, Vol. 99, 1996, 1459-1464.
[8]	W. M. Leach, Jr. , Computer-Aided Electroacoustic Design with SPICE, Journal of Audio Engineering Society, Vol. 39, 1991, 551-563.
[9]	M. Colloms, High Performance Loudspeakers, John Wiley & Sons, Ch ichester, New York, 1997.
[10]	M. Kaltenbacher, M. Rausch, H. Landes, R. Lerch, Numerical Modelling of Electrodynamic Loudspeakers, 8th International IGTE Symposium on Numerical Field Calculation in Electrical Engineering and International TEAM-Workshop, Graz, Austria, 21.-24.September 1998.
[11]	G. S. Kino, Acoustic Waves: Device, Imaging, and Analog Signal Processing., Prentice-Hall, Englewood Cliffs, 1987
[12]	L. Michalowsky, Magnettechnik - Grundlagen und Anwendung, Fachbuchverlag, Leipzig, 1993.
[13]	M. Zollner, E. Zwicker, Elektroakustik, Springer, New York, 1993
[14]	I. Veit, Technische Akustik: Grundlagen d. physikal., physiolog. u. Elektroakustik, Vogel, Würzburg, 1988.
[15]	A. R. Selfridge, Approximate Material Properties in Isotropic Materials, IEEE Trans. Sonics Ultrason., SU-32 vol.3, 1985, 381-394