Last Updated: 20060821, mei
Saturday, October 7, 9:00 am — 10:30 am
P15-1 Linear Array Transducer Technology—Andrew Unruh, Christopher Struck, Tymphany Corporation - Cupertino, CA, USA
The Linear Array Transducer (LAT) is a loudspeaker technology using multiple opposed interleaved diaphragms to create a bass transducer with a cylindrical form factor and almost no mechanical vibration. Design goals, construction, and operating principles are described and frequency response and impedance measurements are shown. Recent structural improvements in the LAT are also discussed. System design considerations are discussed and examples of its use in a product are shown.
Convention Paper 6937 (Purchase now)
P15-2 A Novel Flexible Loudspeaker Driven by an Electret Diaphragm—Dar-Ming Chiang, Jen-Luan Chen, Industrial Technology Research Institute (ITRI) - Chutung, Hsinchu, Taiwan
According to the flexible electronics intensively applied to consumer product in future, a new flexible electrostatic loudspeaker driven by the electret diaphragm is developed. The electret diaphragms of flexible loudspeakers are fabricated by fluoro-polymer with nano-meso-micro pores and charged by the corona method at room temperature. The interior surface areas of the pores of the electret films are effectively to increase the retention and stability of charges. The experimental results reveal that the retention and stability of charges of the electret diaphragm is satisfied to drive the flexible electrostatic loudspeaker. The sound pressure level of the flexible electrostatic loudspeaker (60 mm*80 mm*1 mm) is measured as 80 dB/0.2 W at 1 kHz and 30 cm distance.
Convention Paper 6938 (Purchase now)
P15-3 Stress Analysis on Moving Assemblies and Suspensions of Loudspeakers—Fernando Bolaños, Acústica Beyma S. A. - Valencia, Spain
This paper explains the basic results of numerical and experimental analysis of moving assemblies and suspensions of loudspeakers taking into account the bending forces and the in-plane forces that act on these slender bodies. The distribution of these stresses is shown in cones of direct radiators and in domes (for example, in compression drivers) as well. An explanation of the generation of subharmonics is obtained by this technique. The suddenly jump of the working point on moving assemblies is justified by means of the compression forces that act on the suspensions. These compression forces are the cause of the buckle or snaps that very often occur in the loudspeakers. This paper analyzes different types of suspension showing the compromise situation the designer has to deal with.
Convention Paper 6939 (Purchase now)
P15-4 Nonlinear Stiffness of the Loudspeaker Measured in the Evacuated Space—Ivan Djurek, Faculty of Elec. Eng. and Computing - Zagreb, Croatia; Danijel Djurek, AVAC – Alessandro Volta Applied Ceramics - Zagreb, Croatia; Antonio Petosic, Faculty of Elec. Eng. and Computing - Zagreb, Croatia; Nazif Demoli, Institute of Physics - Zagreb, Croatia
The impedance of the mechanical vibration system of the loudspeaker was measured in vacuo in order to remove the contributions of the radiation impedance of air. The Hooke constant k was evaluated by the use of calibrated weights and from the membrane displacements due to the force exerted by DC current in the voice coil. The resonant frequency was found to decrease with increasing nonlinear Hooke constant, which is attributed to the effective mass of the vibration system, dependent upon elongation. The effective mass was evaluated from the fitting of measured and calculated loudspeaker impedance curve.
Convention Paper 6940 (Purchase now)
P15-5 Linearization of Nonlinear Loudspeakers—Bo Rohde Pedersen, Aalborg University - Esbjerg, Denmark; Per Rubak, Aalborg University - Aalborg, Denmark
Feed forward methods for compensation of nonlinearities in loudspeakers are studied and tested in simulation cases. An adaptive feed forward controller is investigated to handle the drift caused by temperature, aging, and production spread. For estimating the needed parameter accuracy (match between controller and plant parameters) we have tested a simple feed forward controller with different degree off parameter mistuning between plant (loudspeaker) and controller. The required system identification (tracking of the changes in linear loudspeaker parameters) is investigated using and simple 2nd order IIR model for the linear loudspeaker. Different techniques to handle the stability problem for adaptive IIR filters are investigated.
Convention Paper 6941 (Purchase now)
P15-6 Response Adaptation of Loudspeaker System—Mingu Lee, Hyun-Ju Jung, Sinlyul Lee, Koeng-Mo Sung, Seoul National University - Seoul, Korea
In this paper variations in the frequency response of vented-box loudspeakers due to the adjustment of several less constrained physical parameters are predicted. In addition, with this information, estimation of the optimum values of the parameters that the corresponding frequency response optimally fits the arbitrary objective response is accomplished. Also, the MATLAB GUI program, which performs the procedure automatically, with the vented-box loudspeaker parameters as input, is presented. The extendibility of the limitations of this method in terms of the type of the loudspeaker, the optimality criterion, etc., is discussed.
Convention Paper 6942 (Purchase now)
P15-7 Digitally-Driven Piezoelectric Loudspeaker Using Multibit Sigma-Delta Modulation—Hajime Ueno, Tsuyoshi Soga, Katsuya Ogata, Akira Yasuda, Hosei University - Tokyo, Japan
Although a substantial quantity of music data is stored as digital information, as in the case of CDs and MDs, an analog drive is still the main component of a loudspeaker. If the speaker can be driven digitally, it becomes possible to perform all processes from the input to the output digitally. As a result, the analog power amplifier and some other components become unnecessary and a small, light, and high-quality loudspeaker can be achieved. In this paper we propose a digitally-driven piezoelectric speaker employing multibit delta-sigma modulation.
Convention Paper 6943 (Purchase now)
P15-8 Design Considerations for Shallow Subwoofers—Claus Futtrup, Tymphany Corporation - Cupertino, CA, USA
Conventional subwoofers are usually quite deep to accommodate long throw. A shallow subwoofer (SSW) design is presented that aims to maintain the quality of low distortion and long throw bass reproduction. Two design concepts, applicable to larger drivers, are described and results are shown. The result is more bass for a given loudspeaker-depth without compromising the sound quality at low frequencies. One such concept is the sandwich cone, another the strut supported cone. The chosen design of a low profile diaphragm with strut support is described in detail. Another issue is the motor and spider design. Considerations for joint motor and spider design are analyzed for a series of configurations. Advantages and disadvantages of each are described. The chosen design integrates the spider into the motor system to preserve space but still allows for a large diameter spider to be applied.
Convention Paper 6944 (Purchase now)
P15-9 A Plane Wave Transducer: Technology and Applications—Antti Kelloniemi, Kari Mettälä, Panphonics Oy - Espoo, Finland
A plane wave transducer technology is presented with application examples and measurement results. The technology enables high volume manufacturing of audio elements. These new, highly directive audio transducers are beneficial in several uses. A plane wave source exhibits remarkably less geometric attenuation with increasing distance than conventional cone loudspeakers. As the sound is transmitted only to the wanted direction, the amount of reflections deteriorating the sound quality is minimized and the amount of disturbance at surrounding space is diminished. A directive microphone can be produced using the same technology, which in turn enables the construction of a locally controlled active noise cancellation panel.
Convention Paper 6945 (Purchase now)
