v7.0, 20040922, me

Friday, October 29, 4:00 pm – 6:00 pm
Session Z4 Posters: LOUDSPEAKERS, Part 2
NOTE: During the first 10 minutes of the session all authors will present a brief outline of their presentation.

4:00 pm
Z4-1 Impulse Response and Frequency Response of a Line Loudspeaker Array—Chao Jiang, Jian Zou, Yong Shen, Nanjing University, Nanjing, P. R. China
A uniform method is presented to calculate impulse response of an arbitrary point of sound field radiated by a line loudspeaker array. The frequency response is also obtained by applying FFT technology to the impulse response. It is shown that, in any point of a sound field, the frequency response is similar to a low-pass filter, and the cut off frequency varies with the position of the observation point.
Convention Paper 6248

4:00 pm
Z4-2 Real-Time Voice-Coil Temperature and Cone Displacement Control of Loudspeakers—Constâncio Bortoni, Sidnei Noceti Filho, Rui Seara , Rosalfonso Bortoni, Federal University of Santa Catarina, Brazil
With loudspeakers operating in a high power environment (common in PA systems), the voice-coil overheating and the excessive cone displacement are the main causes of damage and faults. These drawbacks are related to the low efficiency and cone displacement limitation, respectively. This paper proposes a procedure to measure and control both the voice-coil temperature and cone displacement by using a digital signal processor (DSP). The voice-coil temperature and cone displacement are indirectly obtained from the coil DC resistance variation and the cone acceleration, respectively. This approach takes into account (by measuring) some real characteristics of the loudspeaker, as its inherent nonlinearities. Thus, we can obtain the most from the sound system, since it may now work without the usual safety margin needed for these systems.
Convention Paper 6249

4:00 pm
Z4-3 Loudspeaker Transducers with an Alternative Tubular Form Factor—Andrew Unruh, Tymphany Corporation, Cupertino, CA, USA; Robert True, True Technologies, Inc. Pleasant Prairie, WI, USA
Three different multi-diaphragm loudspeaker transducers with a tubular form factor are investigated. The transducers consist of a conventional motor structure, a tubular housing, and multiple diaphragms. In one design, sound is generated by the relative motion between a housing that is driven by a single motor and diaphragms that are attached to the housing via flexible surrounds. In a second design, a single motor drives one set of diaphragms and sound is generated by the relative motion between the diaphragms and the fixed housing. In the final design, two motors are used to drive two sets of diaphragms in opposition, and sound is generated by the relative motion between them.
Convention Paper 6250

4:00 pm
Z4-4 Higher Order Harmonic Signature Analysis for Loudspeaker Defect Detection—Dan Foley, Listen, Inc., Boston, MA, USA; Robert Celmer, Benjamin Sachwald, James Anthony, Tony Pagliaro, Shane Thompson, University of Hartford, West Hartford, CT, USA
Loudspeaker assembly faults, such as a rubbing voice coil, bent frame, loose spider, etc., have traditionally been detected using experienced human listeners at the end of a production line. Previous attempts to develop production measurement systems for on-line testing typically analyze only low-order harmonics for the primary purpose of measuring total harmonic distortion (THD), and thus are not specifically designed to detect defective rub, buzz, and ticking sounds. This paper describes a new method wherein the total energy of high-order harmonics groups, for example, 10th through the 20th or 31st through the 40th, are measured and analyzed. By grouping high-order harmonics and resolving their respective total energies, distinct signatures can be obtained that correlate to the root cause of audible rub and buzz distortions (Temme, 2000). The paper discusses loudspeakers tested with specific defects, as well as results of a computer-based electroacoustic measurement and analysis system used for detection.
Convention Paper 6251