AES London 2011
Paper Session P2

P2 - Loudspeakers

Friday, May 13, 09:30 — 12:30 (Room 1)

John Vanderkooy

P2-1 Vibrations in the Loudspeaker Enclosure Evaluated by Hot Wire Anemometry and Laser InterferometryDanijel Djurek, AVAC (Alessandro Volta Applied Ceramics) Laboratory for Nonlinear Dynamics - Zlatar-Bistrica, Croatia; Nazif Demoli, Institute of Physics - Zagreb, Croatia
Vibration states of the loudspeaker enclosure were examined by the laser interferometry and hot wire anemometry. According to simple expressions, air pressure in the enclosure is independent on air density. This statement has been tested by the use of gases indicated by very different densities (air, He, SF6), and interferometric data show a strong dependence of vibration states of the enclosure walls on density, when driving frequency increases from 500 Hz up to 1 kHz. The main reason for a deviation resides in the imaginary part of the Morse impedance exerted by the vibrating gas within the enclosure.
Convention Paper 8321 (Purchase now)

P2-2 Losses and Coupling in Long Multi-Wire Loudspeaker CablesXavier Meynial, Guennolé Gapihan, Active Audio - Saint-Herblain, France
It is quite frequent in PA systems to use very long loudspeaker cables. These PA systems sometimes carry several audio signals in adjacent wires of the same cable, or several cables may be neighboring over very long distances such as several hundreds meters. This paper deals with losses and coupling in these long cables. It is shown that even though losses and coupling may introduce significant crosstalk between wires and affect the amplifier loads, it is possible to use very long loudspeaker cables to connect line arrays in PA systems. Coupling between cables is also investigated, and strategies for reducing losses and coupling are presented.
Convention Paper 8322 (Purchase now)

P2-3 Subwoofers in Rooms: Modal Analysis for Loudspeaker PlacementJuha Backman, Nokia Corporation - Espoo, Finland, Aalto University, Espoo, Finland
Use of multiple subwoofers in a room is known to help in reducing the variation of response both as a function of frequency and a function of place, but simple geometry-based placement rules guarantee good results only in symmetrical cases. The paper discusses the use of experimental modal analysis and numerical optimization based on modal behavior to determine the optimal placement of single or multiple subwoofers in rooms with arbitrary geometry and surface properties.
Convention Paper 8323 (Purchase now)

P2-4 Losses in Loudspeaker EnclosuresClaus Futtrup, Scan Speak A/S - Videbæk, Denmark
In recent papers a lumped parameter model, which can simulate the impedance of conventional electro-dynamic transducers accurately has been presented. The new model includes frequency-dependent damping, which questions traditional engineering practices in simulations of loudspeaker enclosures and, in particular, associated losses. In this paper the consequences of frequency-dependent damping are evaluated to aid the development of simulations and models of loudspeaker enclosures.
Convention Paper 8324 (Purchase now)

P2-5 Comparison of Measurement Methods for the Equalization of Loudspeaker Panels Based on Bending Wave RadiationLars Hörchens, Diemer de Vries, Delft University of Technology - Delft, The Netherlands
Spatially extended panel loudspeakers based on bending wave radiation, such as distributed mode loudspeakers or multi-actuator panels, exhibit a complex radiation pattern with frequency-dependent directivity characteristics. This paper seeks to determine the kind, position, and number of measurements needed to obtain an average radiation spectrum enabling efficient equalization. To this end, three approaches are compared: wave field extrapolation of the panel surface normal velocity, extrapolation of a near-field pressure measurement, and actual in-situ measurements at a number of random positions inside the listening space. The choice of the positions and the required number of measurements are discussed. Measurements taken on a multi-actuator panel are used to compare the different approaches and present numerical results.
Convention Paper 8325 (Purchase now)

P2-6 The Effect of Finite-Sized Baffles on Mobile Device Personal AudioJordan Cheer, Stephen J. Elliott, University of Southampton - Southampton, UK; Youngtae Kim, Jung-Woo Choi, Samsung Electronics Co. Ltd. - Korea
To reduce the annoyance from the use of loudspeakers on mobile devices, previous work has investigated the use of acoustic contrast control to optimize the performance of small arrays of loudspeakers. These investigations have assumed that the baffle dimensions are negligible so that the loudspeakers are omnidirectional, which is reasonable at low frequencies; however, in practice the effect of a finite-sized baffle on the optimized performance is important at higher frequencies. This paper reports the results of using a finite-element model of a two-source array, positioned on a mobile phone sized baffle, to investigate the influence of the baffle on the predicted array performance. The baffle is shown to reduce the performance of the array at frequencies greater than around 1 kHz, but then the directivity of the individual drivers enhances performance at these higher frequencies.
Convention Paper 8326 (Purchase now)

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