AES Warsaw 2015
Poster Session P10
P10 - (Poster) Transducers
Friday, May 8, 16:00 — 18:00 (Foyer)
P10-1 Loudspeaker Systems by Linear Motion Type Piezoelectric Ultrasonic Actuators—Daichi Nagaoka, Tokyo University of Technology - Hachioji-shi, Tokyo, Japan; Juro Ohga, Shibauro Institute of Technology / Mix Corporation - Kanagawa, Japan; Hirokazu Negishi, Mix Corporation - Kanagawa, Japan; Ikuo Oohira, Consultant - Kanagawa-ken, Japan; Kazuaki Maeda, TOA Corporation - Hyogo, Japan; Kunio Oishi, Tokyo University of Technology - Tokyo, Japan
The research group of authors have been developing completely new loudspeaker constructions that are driven by piezoelectric ultrasonic motors. This paper proposes two sorts of applications of piezoelectric linear actuators to both direct radiator and horn loudspeakers. A direct-radiator loudspeaker with a cone radiator driver by piezoelectric actuators shows smooth frequency characteristics in low frequency region because its radiating motion includes no significant resonance in the working frequency region. Therefore, it is useful for radiation of the lowest frequency part of audio signal. A horn loudspeaker by the same actuators works in rather moderate frequency region that is higher than the cut-off frequency of hones of ordinary size.
Convention Paper 9283 (Purchase now)
P10-2 Low Frequency Nonlinear Model for Loudspeaker Transducers—Shaolin Wei, Guo Guang Electric Corporation (GGEC) - Guangzhou, China; Tony Xie, Sr., Guo Guang Electric Corporation (GGEC) - Guangzhou, China; Hunter Huang, Sr., Guo Guang Electric Corporation (GGEC) - Guangzhou, China
In this paper a nonlinear loudspeaker transducer model and its solution are presented. A simple and effective iteration procedure to obtain the solution of the nonlinear equation is proposed. This procedure is a powerful tool for determination of a periodic solution of a non-linear equation of motion. Further, the sound pressure of fundamental, second order, and third order harmonic distortion are also calculated. The solutions obtained using the present iteration method can give the directions to how to lower the second and third harmonics.
Due to unavoidable circumstances this poster will not be presented.
Convention Paper 9284 (Purchase now)
P10-3 Active Control of a String Instrument Bridge Using the Posicast Technique—Liam B. Donovan, Queen Mary University of London - London, UK; Andrew McPherson, Queen Mary University of London - London, UK
This paper presents an active bridge allowing for precise audio-rate manipulation of a string’s termination for the purposes of modifying string instrument timbre. The design of the bridge actuator and height sensor is discussed, and the benefits of using feedforward posicast control over a feedback compensator for controlling the dynamics of the severely underdamped bridge actuator system are established.
Convention Paper 9285 (Purchase now)
P10-4 Efficiency Optimization in Class-D Audio Amplifiers—Akira Yamauchi, Technical University of Denmark - Kgs. Lyngby, Denmark; Arnold Knott, Technical University of Denmark - Kgs. Lyngby, Denmark; Ivan H. H. Jørgensen, Technical University of Denmark - Kgs. Lyngby, Denmark; Michael A. E. Andersen, Technical University of Denmark - Kgs. Lyngby, Denmark
This paper presents a new power efficiency optimization routine for designing Class-D audio amplifiers. The proposed optimization procedure finds design parameters for the power stage and the output filter, and the optimum switching frequency such that the weighted power losses are minimized under the given constraints. The optimization routine is applied to minimize the power losses in a 130 W class-D audio amplifier based on consumer behavior investigations, where the amplifier operates at idle and low power levels most of the time. Experimental results demonstrate that the optimization method can lead to around 30% of efficiency improvement at 1.3 W output power without significant effects both on the audio performances and on the efficiency at high power levels.
Convention Paper 9286 (Purchase now)
P10-5 Investigation of Energy Consumption and Sound Quality for Class-D Audio Amplifiers Using Tracking Power Supplies—Akira Yamauchi, Technical University of Denmark - Kgs. Lyngby, Denmark; Henrik Schneider, Technical University of Denmark - Kgs. Lyngby, Denmark; Arnold Knott, Technical University of Denmark - Kgs. Lyngby, Denmark; Ivan H. H. Jørgensen, Technical University of Denmark - Kgs. Lyngby, Denmark; Michael A. E. Andersen, Technical University of Denmark - Kgs. Lyngby, Denmark
The main advantage of Class-D audio amplifiers is high efficiency that is often stated to be more than 90% but, at idle or low power levels the efficiency is much lower. The waste energy is an environmental concern, a concern in mobile applications where long battery operation is required and a concern in other applications where multiple amplifier channels are generating heat problems. It is found that power losses at low power levels account for close to 78% of energy consumption based on typical consumer behavior investigations. This paper investigates the theoretical limits of ideal stepless power supply tracking and its influence on power losses, audio performance, and environmental impact for a 130 W class-D amplifier. Both modeled and experimental results verify that a large improvement of efficiency can be achieved with a new challenge for a self-oscillating controller to keep the audio quality in such a system. The energy consumption may be reduced by up to 72%. The investigation is extended to a commercialized class-D amplifier as well.
Convention Paper 9287 (Purchase now)
P10-6 Soundbar System with Embedded Multichannel Digital Amplifier SoC—Jeongil Seo, Electronics & Telecom. Research Institute (ETRI) - Daejeon, Korea; Jae-Hyoun Yoo, Electronics and Telecommunications Research Institute (ETRI) - Daejeon, Korea; Taejin Park, Electronics and Telecommunications Research Institute (ETRI) - Daejeon, Korea; Taejin Lee, Electronics and Telecommunications Research Institute (ETRI) - Daejeon, Korea; Myunggeun Yoo, NeoFidelity - Seongnam-si, Gyeonggi-do, Korea; Geunho Jang, NeoFidelity - Seongnam-si, Gyeonggi-do, Korea; Jae-Hee Won, NeoFidelity - Seongnam-si, Gyeonggi-do, Korea; Yeongha Choi, NeoFidelity, Inc. - Seongnamsi, Kyunggido, Korea
This paper presents collaboration approach results between an audio signal processing algorithm and a digital amplifier structure for efficient implementation of soundbar applications. If we want to provide a virtual surround sound image with a linear loudspeaker array, high performance DSP and multichannel digital amplifiers are required. The required performance for DSP is depended on the algorithm complexity for creating a virtual surround sound image. However the final computation before generating the output loudspeaker signals (e.g., 16 channels) is generally composed of simple delay and sum computations from an input audio signal (e.g., 5.1 channels) to output multichannel loudspeaker signals. Therefore we redesigned the audio signal processing software by two-block processing, and the second block for simple delay and sum computation is implemented at the multichannel digital amplifier, which has an independent DSP core. Through computational simulation and hardware implementation, the proposed system showed equivalent performance with the conventional one block processing system.
Convention Paper 9288 (Purchase now)
P10-7 Loudspeaker Impedance Emulator for Multi Resonant Systems—Niels Elkjær Iversen, Technical University of Denmark - Kongens Lyngby, Denmark; Danmark; Arnold Knott, Technical University of Denmark - Kgs. Lyngby, Denmark
Specifying the performance of audio amplifiers is typically done by playing sine waves into a pure ohmic load. However real loudspeaker impedances are not purely ohmic but characterized by its electrical, mechanical, and acoustical properties. Therefore a loudspeaker emulator capable of adjusting its impedance to that of a given loudspeaker is desired for measurement purposes. An adjustable RLC-based emulator is implemented with switch controlled capacitors, air gap controlled inductors, and potentiometers. Calculations and experimental results are compared and show that it is possible to emulate the loudspeaker impedance infinite baffle-, closed box-, and the multi resonant vented box-loudspeaker by tuning the component values in the proposed circuit. Future work is outlined and encouraged that the proposed impedance emulator is used as part of a control circuit in a switch-mode based impedance emulator.
Convention Paper 9289 (Purchase now)
P10-8 How "Green" Is My Amp?—Jamie Angus, University of Salford - Salford, Greater Manchester, UK
This paper examines the potential threat of power restriction legislation on audio power amplifier design. By considering the interaction between the amplitude distribution of audio signals with the efficiency characteristics of the different amplifier classes it shows that some of the linear classes can perform well as regards energy consumption and thus can compete with switching class D systems. Furthermore, it discusses the possibility of optimizing some of the linear amplifier classes in conjunction with the amplitude probabilities of real audio signals to effect a further reduction in average power consumption. Thus resulting in the "greenest possible" amplifier for a given class of power amplification.
Convention Paper 9290 (Purchase now)
P10-9 An Investigation into Utilizing Opto-Sensors to Function as Parts of MIDI Controllers—Richard Corke, Southampton Solent University - Southampton, UK; Andrew J. Horsburgh, Southampton Solent University - Southampton, UK
The presented research focuses on the application of MIDI controllers utilizing opto-sensors to read and translate physical contact into controllable MIDI information. The described technology was found to provide improved interaction and degree of movement translation with other MIDI-capable devices. To demonstrate this, a projection controller using existing infrared technology will be used in conjunction with a microcontroller allowing for communication between analog and digital control signals.
Convention Paper 9291 (Purchase now)
P10-10 Investigation of Current Driven Loudspeakers—Henrik Schneider, Technical University of Denmark - Kgs. Lyngby, Denmark; Finn T. Agerkvist, Technical University of Denmark - Kgs. Lyngby, Denmark; Arnold Knott, Technical University of Denmark - Kgs. Lyngby, Denmark; Michael A. E. Andersen, Technical University of Denmark - Kgs. Lyngby, Denmark
Current driven loudspeakers have previously been investigated but the literature is limited and the advantages and disadvantages are yet to be fully identified. This paper makes use of a non-linear loudspeaker model to analyze loudspeakers with distinct non-linear characteristics under voltage and current drive. A multi tone test signal is used in the evaluation of the driving schemes since it resembles audio signals to a higher degree than the signals used in total harmonic distortion and intermodulation distortion test methods. It is found that current drive is superior over voltage drive in a 5" woofer where a copper ring in the pole piece has not been implemented to compensate for eddy currents. However the drive method seems to be irrelevant for a 5" woofer where the compliance, force factor as well as the voice coil inductance has been optimized for linearity.
Convention Paper 9292 (Purchase now)
P10-11 Design and Evaluation of Accelerometer-Based Motional Feedback—Henrik Schneider, Technical University of Denmark - Kgs. Lyngby, Denmark; Emilio Pranjic, Technical University of Denmark - Kongens Lyngby, Denmark; Finn T. Agerkvist, Technical University of Denmark - Kgs. Lyngby, Denmark; Arnold Knott, Technical University of Denmark - Kgs. Lyngby, Denmark; Michael A. E. Andersen, Technical University of Denmark - Kgs. Lyngby, Denmark
The electro dynamic loudspeaker is often referred to as the weakest link in the audio chain due to low efficiency and high distortion levels at low frequencies and high diaphragm excursion. Compensating for loudspeaker non-linearities using feedback or feedforward methods can improve the distortion and enable radical design changes in the loudspeaker that can lead to efficiency improvements. In combination this has motivated a revisit of the accelerometer-based motional feedback technique. Experimental results on an 8-inch subwoofer show that the total harmonic distortion can be significantly reduced at low frequencies and large displacements.
Convention Paper 9293 (Purchase now)
