Last Updated: 20050816, mei
P11 - Loudspeakers -1
Sunday, October 9, 9:00 am — 12:00 pm
Chair: Wolfgang Klippel, Klippel GmbH - Dresden, Germany
P11-1 Wideband Piezoelectric Rectangular Loudspeaker Using A Tuck Shape PVDF Bimorph—Toshinori Ouchi, Juro Ohga, Shibaura Institute of Technology - Minato-ku, Tokyo, Japan; Toshitaka Takei, Take T Co. - Kanagawa, Japan; Nobuhiro Moriyama, Kureha Chemical Industry Co. - Tyuou-ku, Tokyo Japan
A bimorph sheet of PVDF (polyvinylidenfluoride) film is applied to a flat rectangular loudspeaker as a folded zigzag-tack shape diaphragm whose size is, for example, 260 mm x 144 mm with various depths. These loudspeakers are characterized by moderate size with a wide frequency range, light weight, and no magnetic flux radiation. This paper examines the electro-acoustic transducer characteristics of this loudspeaker. Sensitivity and resonant frequency were measured by using both a flat panel baffle and a closed box. Theoretical estimation was carried out by thin curved beam theory. The estimated values are compared to the measured results.
Convention Paper 6579 (Purchase now)
P11-2 A Proposal for Low Frequency Loudspeaker Design Utilizing Ultrasonic Motor—Juro Ohga, Shibaura Institute of Technology - Tokyo, Japan; Hirokazu Negishi, DiMagic Co. Ltd. - Tokyo, Japan; Ikuo Oohira, Ashida Sound Co. - Tokyo Japan
Limitations of low frequency sound reproduction ability of the conventional direct-radiator loudspeakers is essential because the diaphragm of them must be driven in a mass-controlled range for a flat response. This paper proposes a novel direct-radiator loudspeaker suitable for low-frequency signal radiation. It utilizes an ultrasonic motor (USM) including a piezoelectric transducer. A velocity modulated continuous revolution is better than a reciprocal motion to avoid distortion in wave form due to the difference between dynamic and static frictional forces. A few fundamental ideas, a continuously revolving flat radiator, an air-flow modulation type without any mechanical radiator, and a conventional radiator actuated by a revolving mass are compared to investigate the merits of the loudspeaker proposed here.
Convention Paper 6581 (Purchase now)
P11-3 Finite Element Modeling of a Loudspeaker. Part 1: Theory and Validation—David Henwood, Brighton University - Brighton, UK; Gary Geaves, B&W Group Ltd. - Steyning, W. Sussex, UK
The paper describes finite element modeling of an axi-symmetric loudspeaker and the resulting predicted behavior, both the motion and the resulting sound pressure field, in both the time and frequency domains. The effect of the electrical circuit is included through postprocessing. Laser and impedance measurements are shown to aid the estimation of the material parameters. Predictions are compared with measured responses and are seen to represent the main features accurately. A significant spider resonance is described. Modes can be loosely classified by the position of their dominant motion, in the spider, cone or surround. This understanding of the modal structure is used in a study of trying to reduce the influence of a cone mode by varying a surround parameter (thickness). An additional paper, Part 2 at this conference, describes applications of the model.
Convention Paper 6582 (Purchase now)
P11-4 Radiated Sound Field Analysis of Loudspeaker Systems: Discrete Geometrical Distribution of Circular Membranes versus Co-Incident Annular Rings—Bernard Debail, Cabasse Acoustic Center - Plouzané, France; Hmaied Shaiek, GET - Brest Cedex, France
This paper addresses the problem of the spatial distribution of sound pressure generated by an annular membrane. A generalized theoretical approach will be developed in order to predetermine the sound field radiation of a disc or ring-shaped diaphragm, placed in a rigid infinite baffle. Because no assumption is made regarding the observing point, this generalized method is able to predict the acoustic pressure not only in the far field region but also in near field. Results demonstrate the superiority of the co-incident ring distribution compared to the traditional discrete distribution of discs. A new transducer based on concentric ring and disc especially designed to respect this coincident criterion will be introduced.
Convention Paper 6583 (Purchase now)
P11-5 Loudspeaker Nonlinearities— Causes, Parameters, Symptoms—Wolfgang Klippel, Klippel GmbH - Dresden, Germany
The paper addresses the relationship between nonlinear distortion measurement and nonlinearities, which are the physical causes for signal distortion in loudspeakers, headphones, micro-speakers, and other transducers. Using simulation techniques, characteristic symptoms are found for each nonlinearity and presented systematically in a guide for loudspeaker diagnostics. This information is important for the interpretation of nonlinear parameters and for performing measurements that describe the loudspeaker more comprehensively. The practical application of the new techniques are demonstrated on three different loudspeakers.
Convention Paper 6584 (Purchase now)
P11-6 Modeling Compression Drivers Using T-Matrices and Finite Element Analysis—David J. Murphy, Krix Loudspeakers - Hackham, SA, Australia; Rick Morgans, Consultant - Australia
Models for a commercial compression driver were developed using transmission line matrices and finite element analysis using the commercial package ANSYS. The models were compared with measurements using plane wave tube loading and discrepancies were investigated. The electrical impedance was measured in-vacuo to obtain Thiele-Small parameters without acoustic loading. A resonance was investigated and found to be air leakage into the magnet cavity. The development of frequency dependent damping in the matrix and FEA models was necessary to improve the simulation accuracy.
Convention Paper 6580 (Purchase now)