Friday, October 10 2:00 pm – 4:00 pm
Session B Loudspeakers, Part 1

B-1 An Acoustical Measurement Method for the Derivation of Loudspeaker Parameters—Brian E. Anderson, Timothy W. Leishman, Brigham Young University, Provo, UT, USA
Because loudspeaker drivers are electro-mechano-acoustical transducers, their parameters may be measured from physical domains other than the electrical domain. A method has been developed by the authors to determine moving-coil loudspeaker parameters through the use of acoustical measurements. The technique utilizes a plane wave tube and the two-microphone transfer function technique to measure acoustical properties of a baffled driver under test (DUT). Quantities such as the reflection and transmission coefficients of the DUT are first measured. Driver parameters are then extracted from the measurements using curve-fitting techniques and theoretical solutions to equivalent circuits of the composite system. This paper discusses the acoustical measurement apparatus, system modeling, and a comparison of acoustically measured parameters to those measured using common electrical techniques. Parameters derived from the various methods are also compared to reference parameters to establish bias errors.

B-2 The Active Pulse-Modulated Transducer (AT)—A Novel Audio Power Conversion System Architecture—Karsten Nielsen, Lars Michael Fenger, Bang & Olufsen ICEpower a/s, Copenhagen, Denmark
A novel audio power conversion system architecture is presented in the attempt to provide a step forward in overall system efficiency and performance. The active pulse-modulated transducer system converts power directly from AC mains or from a DC power supply to the acoustic output in one simplified topological stage.

B-3 Implementation of a Wide-Bandwidth, Digitally Steered Array—Nathan Butler, David Gunness, Eastern Acoustic Works, Inc., Whitinsville, MA, USA
Many potential applications of digital steering require a wide bandwidth implementation in order to benefit from the flexibility and control offered by this technique. The requirements for effective steering are explained with examples and used to establish physical criteria for a practically useful system. An implementation is described which meets these criteria with a high-density, multi-way source array and integrated processing and amplification. The design parameters, the capabilities, and the practical limitations of this system will be explored and demonstrated.

B-4 Low-Frequency Polar Pattern Control for Improved In-Room Response—Juha Backman, Nokia Mobile Phones, Espoo, Finland; Helsinki University of Technology, Espoo, Finland
A loudspeaker arrangement, consisting of two individual drivers and delay units, having omnidirectional polar pattern at low frequencies and first-order gradient pattern at middle frequencies is presented. This system combines the low-frequency dynamic range of conventional speakers with the ability of gradient speakers to reduce room-induced coloration. The benefits and limitations of mid-frequency directivity are analyzed through simulations of room-speaker interaction for omnidirectional, cardioid, and dipole loudspeakers.