Thursday, September 29, 10:45 am — 12:15 pm (Rm 403A)
Christopher Struck, CJS Labs - San Francisco, CA, USA; Acoustical Society of America
P3-1 Power Considerations for Distortion Reduction of Loudspeakers—Ajay Iyer, Harman International - Salt Lake City, UT, USA; Douglas J. Button, Harman International - Northridge, CA USA; Russell H. Lambert, Harman International - Salt Lake City, UT, USA
Over the last 25 years, scientists and engineers have written extensively about methods to reduce distortion in loudspeakers with Digital Signal Processing (DSP). Despite the several proposed solutions, no formal product exists on the market today that employs distortion reduction. In this paper the answer to some fundamental questions about what is required to make substantial improvements in loudspeaker performance is investigated through computer simulations. This research examines the level of volume achievable while still maintaining acceptable levels of distortion. Transducer designs that are best suited for this application are studied and identified.
Convention Paper 9605 (Purchase now)
P3-2 Improving the Sound Balance with Dynamic Control of Membrane Excursion—Mikhail Pahomov, LG Electronics, Inc. - St. Petersburg, Russia; Ivan S. Tolokonnikov, LG Electronics Inc. - St. Petersburg, Russia; Victor Rozhnov, LG Electronics Inc. - St. Petersburg, Russia; Mikhail Gusev, LG Electronics Inc. - St. Petersburg, Russia
The electrodynamic transducers’ that are used in mobile devices are typically prone to voice coil overheating and excessive excursion of the membrane. The paper focuses on the second aspect. Nonlinear distortion is known to depend on membrane excursion amplitude. High sound pressure at low frequencies also requires the maximum vibration amplitude. But now the sound balance is at stake. Thus, we face the challenge of finding the optimal relation between the sound balance and the level of audible distortion to obtain the maximum subjective quality evaluation.
Convention Paper 9606 (Purchase now)
P3-3 Force Factor Modulation in Electro Dynamic Loudspeakers—Lars Risbo, Purifi - Hvalsoe, Denmark; Finn T. Agerkvist, Technical University of Denmark - Kgs. Lyngby, Denmark; Carsten Tinggaard, PointSource Acoustics - Roskilde, Denmark; Morten Halvorsen, PointSource Acoustics - Roskilde, Denmark; Bruno Putzeys, Purifi - Rotselaar, Belgium
The relationship between the non-linear phenomenon of “reluctance force” and the position dependency of the voice coil inductance was established in 1949 by Cunningham, who called it “magnetic attraction force.” This paper revisits Cunningham’s analysis and expands it into a generalized form that includes the frequency dependency and applies to coils with non-inductive (lossy) blocked-impedance. The paper also demonstrates that Cunningham’s force can be explained physically as a modulation of the force factor that again is directly linked to modulation of the flux of the coil. A verification based on both experiments and simulations is presented along discussions of the impact of force factor modulation for various motor topologies. Finally, it is shown that the popular L2R2 coil impedance model does not correctly predict the force unless the new analysis is applied.
Convention Paper 9607 (Purchase now)