AES Budapest 2012
Paper Session P20
P20 - Transducers
Sunday, April 29, 09:00 — 11:30 (Room: Lehar)
P20-1 Loudspeaker for Low Frequency Signal Driven by Four Piezoelectric Ultrasonic Motors—Juro Ohga, Shibaura Institute of Technology/MIX Corporation - Kamakura, Japan; Ryousuke Suzuki, Keita Ishikawa, Chiba Institute of Technology - Narashino, Japan; Hirokazu Negishi, MIX Corporation - Yokosuka, Japan; Ikuo Oohira, I. Oohira and Associates - Yokohama, Japan; Kazuaki Maeda, TOA Corporation - Takarazuka, Japan; Hajime Kubota, Chiba Institute of Technology - Narashino, Japan
The authors have been developing a completely new direct-radiator loudspeaker construction that is driven by continuous revolution of piezoelectric ultrasonic motors. It converts continuous revolution of ultrasonic motors to reciprocal motion of a cone radiator. This loudspeaker shows almost flat phase frequency characteristics in low frequency region, because it includes no resonance in low frequency region. Therefore it is useful for radiation of the lowest frequency part of the audio signal. At this convention the authors are going to present a practical model of this loudspeaker driven by co-operation of four ultrasonic motors.
Convention Paper 8670 (Purchase now)
P20-2 Comprehensive Measurements of Head Influence on a Supercardioid Microphone—Hannes Pomberger, Franz Zotter, University of Music and Performing Arts Graz - Graz, Austria; Dominik Biba, AKG Acoustics GmbH - Vienna, Austria
The directional pickup pattern of microphones is designed as to assist the audio engineer in avoiding acoustic feedbacks or interference from other sound sources. If the pattern deviates from the specified one, it is important for the audio engineer to know. This paper presents comprehensive measurements of a supercardioid microphone directivity under the influence of a dummy head. This dummy models the diffraction of a human talker or singer in front of the microphone. The discussed measurements collect information on a 15x15 degree grid in azimuth and elevation for different distances between the microphone and dummy head. Based on this data, we are able to discuss the influence of a singer’s body on the free field directivity of the supercardioid microphone, its directivity index, and its front-to-back random ratio in detail.
Convention Paper 8671 (Purchase now)
P20-3 Simulation of a 4” Compression Driver Using a Fully Coupled Vibroacoustic Finite Element Analysis including Viscous and Thermal Losses—René Christensen, Ulrik Skov, iCapture ApS - Gadstrup, Denmark
A 4” JBL compression driver is simulated using a finite element alanysis, FEA. Compared to a conventional electrodynamic driver a compression driver has a phase plug with slits in front of the diaphragm. The slits are acoustically narrow and the diaphragm is separated from the phase plug only by a thin gap so an accurate model must include viscothermal effects to account for the losses associated with the narrow air gaps. Air domains, structural domains, and viscothermal domains are all fully coupled to ensure the proper continuity of their variables. Simulated results are compared to experimental measurements and it is demonstrated how the viscothermal effects dampen out acoustic and structural modes.
Convention Paper 8672 (Purchase now)
P20-4 Design of Vented Boxes Using Current Feedback Filters—Juha Backman, Nokia Corporation - Espoo, Finland; Tim Mellow, MWT Acoustics - Farnham, Surrey, UK
A current feedback arrangement for a loudspeaker system that can be tuned to provide a pre-determined frequency-response shape over a fairly wide and continuous range of box volumes is discussed. A conventional high-pass filter only allows the system to be tuned to give a particular frequency-response shape if the box volume is correct. The traditional arrangement is either a flat response amplifier, a passive filter between the amplifier and loudspeaker, or an active filter before the amplifier. This paper discusses an alternative arrangement where current feedback and filter provide the desired amplifier output impedance and voltage transfer function characteristics. These interact directly with the complex load-impedance of the loudspeaker. Practical realizations of the current feedback implementations are presented.
Convention Paper 8673 (Purchase now)
P20-5 Midrange Coloration Caused by Resonant Scattering in Loudspeakers—Juha Backman, Nokia Corporation - Espoo, Finland
One of the significant sources of midrange coloration in loudspeakers is the resonant scattering of the exterior sound field from ports, recesses, or horns. This paper discusses a computationally efficient model for such scattering, based on waveguide models for the acoustical elements (ports, etc.), and mutual radiation impedance model for their coupling to the sound field generated by the drivers. This allows rapid evaluation of the effect of port placement, suitable for numerical optimization of loudspeaker enclosure layouts.
Convention Paper 8674 (Purchase now)
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