Last Updated: 20050401, meiMonday, May 30, 09:00 — 13:00
Chair: David Clark, DLC Design - Wixom, MI, USA
J-1 Direct Acoustic Digital to Analog Conversion with Digital Transducer Array Loudspeakers—Jorge Mendoza-Lopez, Simon C. Busbridge, University of Brighton - Brighton, East Sussex, UK; Peter A. Fryer, B&W Loudspeakers Ltd. - Steyning, West Sussex, UK
A digital transducer array (DTA) loudspeaker, which produces a quantized sound field directly from binary-weighted bit streams has been developed. Theoretical investigation shows that it is possible to generate an acoustic wavefront from an assemblage of air quanta. Line and circular DTA prototypes made of moving coil-transducers are studied in terms of frequency response and total harmonic distortion measurements. Other acoustic effects, e.g., filtering are presented. Results obtained with newly developed stiff diamond diaphragms demonstrate the importance of the transient response to the conversion process. Further results and simulations are presented comparing different transducer diaphragm materials and giving the DTA sound field distortion for different array geometries.
Convention Paper 6417 (Purchase now)
J-2 Structural and Acoustic Analysis of Multi-Actuator Panels—Martin Kuster, Fraunhofer Institut Digitale Medientechnologie IDMT - Ilmenau, Germany; Diemer de Vries, Delft University of Technology - Delft, The Netherlands; Daniel Beer, Sandra Brix, Fraunhofer Institut Digitale Medientechnologie IDMT - Ilmenau, Germany
Multi-actuator panels (MAPs) are a possible solution to satisfy the requirement of a large number of loudspeaker channels inherent in wave field synthesis. The structural acoustic behavior of Multi-Actuator Panels has been measured with a laser doppler vibrometer, and acoustic radiation simulation has been performed using a discretized Rayleigh I integral. The analysis shows that, due to the large structural damping, the acoustic radiation is almost entirely produced by the near-field around the excitation point on the panel. It is concluded that the model of an infinite panel is more appropriate than that of the widely known distributed mode loudspeaker when describing the panel’s performance.
Convention Paper 6418 (Purchase now)
J-3 On the Sound Field of a Membrane in an Infinite Baffle—Tim Mellow, Nokia UK Ltd. - Farnborough, UK; Leo Kärkkäinen, Nokia Research Center - Helsinki, Finland
The sound radiation characteristics of a fluid-loaded membrane are calculated analytically and use a finite element model. It is shown that good correlation between the two calculation methods can be achieved, providing the elements are small enough. The model can be applied to electrostatic or other membrane type loudspeakers with a very large back cavity. Although this is seldom possible in practice, this model provides an indication of what the theoretical limit of the bass performance actually is as well as an analytical benchmark for the finite element modeling of fluid-structure coupled problems.
Convention Paper 6419 (Purchase now)
J-4 Influence of Material and Shape on Sound Reproduction by an Electrodynamic Loudspeaker—Nicolas Quaegebeur, Antoine Chaigne, UME, ENSTA (École Nationale Supérieure de Techniques Avancées) - Palaiseau, France
A key point in electroacoustics is to determine the transfer function between an input electrical signal and the radiated sound pressure. Since electrodynamic transducers radiate in a large frequency range, lumped parameter models are usually not sufficient to provide a realistic simulation of the vibroacoustical behavior of the system. In this paper preliminary results on the use of modal equations for predicting the time domain sound field in free space radiated by a spherical shell in the audible range are presented.
Convention Paper 6420 (Purchase now)
J-5 An Alternative Approach to Minimize Inductance and Related Distortions in Loudspeakers—Marco Carlisi, Mario Di Cola, Audio Labs Systems - Milan, Italy; Andrea Manzini, 18 Sound, a Division of A.E.B. S.r.l. - Cavriago, Reggio Emilia, Italy
Magneto-dynamic loudspeakers are affected from a wide variety of problems due to the voice coil inductance. This inductance is not a constant parameter but is dependent on the frequency, the displacement, and the actual current flowing in the coil. Moreover these last two dependencies are also nonlinear. Several causes of distortion, affecting mainly the vocal range, are derived from these phenomena. A practical solution to minimize the inductance is investigated. This solution is based on an additional fixed coil positioned in the gap provided with two additional terminals offering various connection possibilities. This device is referred to AIC (Active Impedance Control). Advantages of this approach will be discussed and measurement results will be shown as well.
Convention Paper 6421 (Purchase now)
J-6 Large Signal Performance of Tweeters, Micro Speakers, and Horn Drivers—Wolfgang Klippel, Klippel GmbH - Dresden, Germany
Loudspeakers dedicated to high-frequency signals may also produce significant distortion in the acoustical output. The nonlinearities in motor and suspension can be modeled by equivalent circuits and dynamically measured by a system identification technique-based voltage and current monitoring. The identified model is the basis for numerical prediction of the large signal performance and reveals the effect of each nonlinearity. The paper uses this technique for the diagnosis of three different drivers, compares measured and predicted distortion, investigates the thermal power compression, and discusses the impact on the perceived sound quality.
Convention Paper 6422 (Purchase now)
J-7 Linear Phase Analog Crossover Systems Revisited—Neville Thiele, The University of Sydney - Sydney, Australia
Design procedures and worked examples are described for asymmetrical linear phase, or "constant voltage," crossover systems whose summed output remains constant, "flat," in amplitude and phase response across the whole audio spectrum without making impractical demands on the power handling capability or precision of their components. Alternative procedures are demonstrated for optimum performance in respect of power handling, cone excursion, and equalization.
Convention Paper 6423 (Purchase now)
J-8 DSP-Based Sensorless Velocity Observer with Audio Applications in Loudspeaker Compensation—Mingsian Bai, Chih-Chung Lee, National Chiao-Tung University - Hsin-Chu, Taiwan
Cone velocity of loudspeakers has been long recognized as an important parameter for loudspeaker compensation. In this paper a cone velocity observer that requires no sensor is developed on the basis of state-space estimation. Linear quadratic Gaussian (LQG) theory in conjunction with multirate processing is employed in the design of the observer. The experimental results show close agreement between the velocities obtained by using the proposed technique and the measurement by a laser vibrometer. In addition, the system allows for self-identification and automated filter synthesis. The compensation filters are designed using the quantitative feedback technique (QFT) and implemented on a digital signal processor (DSP). The system is applied to two audio problems in loudspeaker compensation: bass enhancement and room response equalization. Experimental results are discussed.
Convention Paper 6424 (Purchase now)
©2005 Audio Engineering Society, Inc.