AES New York 2009
Paper Session P12

P12 - Transducers Manufacturing and Equipment

Sunday, October 11, 9:00 am — 1:00 pm
Chair: Alexander Voishvillo

P12-1 Time Varying Behavior of the Loudspeaker Suspension: Displacement Level Dependency—Finn Agerkvist, Technical University of Denmark - Lyngby, Denmark; Bo Rhode Petersen, Esbjerg Institute of Technology, Aalborg University - Aalborg, Denmark
The compliance of the loudspeaker suspension is known to depend on the recent excitation level history. Previous investigations have shown that the electrical power as well as displacement and velocity plays a role. In this paper the hypothesis that the changes in compliance are caused mainly by how much the suspension has been stretched, i.e., the maximum displacement, is investigated. For this purpose the changes in compliance are measured when exposing the loudspeaker to different levels and types of electrical excitation signals, as well as mechanical excitation only. For sinusoidal excitation the change in compliance is shown to depend primarily on maximum displacement. But for square pulse excitation the duration of the excitation also plays an important role.
Convention Paper 7902 (Purchase now)

P12-2 Fast Measurement of Motor and Suspension Nonlinearities in Loudspeaker Manufacturing—Wolfgang Klippel, University of Technology Dresden - Dresden, Germany; Joachim Schlechter, KLIPPEL GmbH - Dresden, Germany
Nonlinear distortions are measured at the end of the assembling line to check the loudspeaker system and to make a pass/fail decision. However, the responses of single components and total harmonic distortion have a low diagnostic value because they are difficult to interpret and do not reveal the particular cause of the defect. A new measurement technique is presented that measures the nonlinearities of motor and suspension system directly. The results are single-valued parameters (e.g., voice coil offset in mm), which are directly related with the geometry and large signal parameters of the loudspeaker system. The measurement is only based on the measurement of the electrical signals at the speaker’s terminals giving full robustness against ambient noise. The accuracy of the measurement results is investigated while performing measurements using short stimuli between 0.2 and 1.3 seconds. The paper discusses new possibilities for on-line diagnostic during end-of-line testing and the integration into production control to increase the yield of the production.
Convention Paper 7903 (Purchase now)

P12-3 A Novel Technique for Detecting and Locating Loudspeaker Defects—Yi Yang, Junfeng Wei, Haihong Feng, Zhoubin Wen, Chinese Academy of Sciences - Beijing, China
A novel technique for the measurement of rub and buzz using a fast tracking high pass filter is presented first in this paper. In the tests of 100,000 loudspeaker samples on a production line, the very low missed detection was 0.006% and the false alarm rate was 4.68% with this method compared with human hearing tests. Then a method consisted of detecting loudspeaker defect and estimating loudspeaker displacement without using a laser displacement sensor is launched. Only the current response of the loudspeaker is used to predict loudspeaker displacement. And there is less than 3% error in phase component according to the direct laser measurement. Several experiments proved this method was very effective.
Convention Paper 7904 (Purchase now)

P12-4 Practical Measurement of Loudspeaker Distortion Using a Simplified Auditory Perceptual Model—Steve Temme, Pascal Brunet, Listen Inc. - Boston, MA, USA; D. B. (Don) Keele Jr., DBK Associates and Labs - Bloomington, IN, USA
Manufacturing defects in loudspeaker production can often be identified by an increase in rub and buzz distortion. This type of distortion is quite noticeable because it contributes an edgy sound to the reproduction and is annoying because it often sounds separate or disembodied from the fundamental signal. The annoyance of rub and buzz distortion is tied intimately to human perception of sound and psychoacoustics. To properly implement automated production-line testing of loudspeaker rub and buzz defects, one has to model or imitate the hearing process using a sufficiently accurate perceptual model. This paper describes the results of a rub and buzz detection system using a simplified perceptual model based on human masking thresholds that yields excellent results.
Convention Paper 7905 (Purchase now)

P12-5 The Audio Performance Comparison and Effective Error Correction Method of Switching Amplifiers—Jae Cheol Lee, Haekwang park, Donghyun Lim, Joonhyun Lee, Yongserk Kim, Samsung Electronics Co., Ltd.
This paper introduces various open-loop and closed-loop switching amplifiers and then reviews merits and demerits when they are applied to consumer electronic products. Audio specifications in products that open-loop and closed-loop switching amplifiers are adopted to are measured and analyzed as to whether they have weak points. After that, the paper proposes a simple and effective method for the error control. The proposed method has the outstanding audio performance in consumer electronics products.
Convention Paper 7906 (Purchase now)

P12-6 Investigation of Switching Frequency Variations and EMI Properties in Self-Oscillating Class D Amplifiers—Dennis Nielsen, Arnold Knott, Technical University of Denmark - Lyngby, Denmark; Gerhard Pfaffinger, Harman/Becker Automotive Systems GmbH - Straubing, Germany; Michael Andreas E. Andersen, Technical University of Denmark - Lyngby, Denmark
Class D audio amplifiers have gained significant influence in sound reproduction due to their high efficiency. One of the most commonly used control methods in these amplifiers is self-oscillation. A parameter of key interest in self-oscillating amplifiers is the switching frequency, which is known for its variation. Knowledge of switching frequency variations is of great importance with respect to electromagnetic interference (EMI). This paper will investigate whether the switching frequency is depended on modulation index and audio reference frequency. Validation is done using simulations, and the results are compared with measurements performed on a 50 W prototype amplifier. The switching frequency is tracked through accurate spectrum measurements, and very good compliance with simulation results are observed.
Convention Paper 7907 (Purchase now)

P12-7 Design Optimizations for a High Performance Handheld Audio Analyzer—Markus Becker, NTi Audio AG - Schaan, Liechtenstein
All types of advanced mobile devices share certain design challenges. For example, incorporating a powerful embedded processor system to support comprehensive functionality via a full featured easy-to-use human interface at low power consumption. But designing a multi-function handheld audio analyzer adds further challenges based upon requirements for extremely low noise floor, wide measurement range, compatibility with measuring microphones and other demands, including standards compliance. Additional requirements include the efficient display of complex data onto a restricted size display, and efficient and safe operation in many different locations and environments. These place further design burdens on the user interface and the instrument package, respectively.
Convention Paper 7908 (Purchase now)

P12-8 The 48 Volt Phantom Menace Returns—Rosalfonso Bortoni, Wayne Kirkwood, THAT Corporation - Milford, MA, USA
Hebert and Thomas presented a paper at the 110th AES Convention [Convention Paper 5335] that described the “phantom menace” phenomenon wherein microphone phantom power faults can damage audio input circuitry. Now, a few years later, this paper brings and provides new information about the phantom menace fault mechanisms, analyzes common protection circuits, and introduces a new protection scheme that is more robust. In addition, new information is presented relating these input protection schemes to audio performance and recommendations are made to minimize noise and distortion.
Convention Paper 7909 (Purchase now)