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AES Amsterdam 2008
Paper Session P1

P1 - Loudspeakers - 1

Saturday, May 17, 09:00 — 12:00
Chair: Stanley Lipshitz, University of Waterloo - Waterloo, Ontario, Canada

P1-1 Audio Capacitors. Myth or Reality? Philip Duncan, University of Salford - Salford, Greater Manchester, UK; Paul Dodds, Nigel Williams, ICW, Ltd. - Wrexham, Wales, UK
This paper gives an account of work carried out to assess the effects of metallized film polypropylene crossover capacitors on key sonic attributes of reproduced sound. The capacitors under investigation were found to be mechanically resonant within the audio frequency band, and results obtained from subjective listening tests have shown this to have a measurable effect on audio delivery. The listening test methodology employed in this study evolved from initial ABX type tests with set program material to the final A/B tests where trained test subjects used program material that they were familiar with. The main findings were that capacitors used in crossover circuitry can exhibit mechanical resonance, and that maximizing the listener’s control over the listening situation and minimizing stress to the listener were necessary to obtain meaningful subjective test results.
Convention Paper 7314 (Purchase now)

P1-2 Perceptual Study and Auditory Analysis on Digital Crossover Filters Henri Korhola, Matti Karjalainen, Helsinki University of Technology - Espoo, Finland
Digital crossover filters offer interesting possibilities for sound reproduction, but there does not exist many publications on how they behave perceptually. In this paper phase and magnitude errors in digital implementations of linear phase FIR as well as Linkwitz-Riley crossover filters are studied perceptually and by auditory analysis. In a headphone simulation listening experiment we explored the just noticeable level of degradation due to crossover filter artifacts. In a real loudspeaker experiment we explored rough guidelines for "safe" filter orders of linear-phase FIR crossover filters, which would not produce audible errors. Possibilities to predict the perceived errors were then explored using auditory analysis, including also third-octave magnitude spectrum and group delay as simple auditory correlates. Linear-phase FIR crossovers were found to produce different kinds of phase errors than Linkwitz-Riley crossovers. The auditory analysis can qualitatively explain the perceptibility degradation.
Convention Paper 7315 (Purchase now)

P1-3 The Air Spring Effect of Flat Panel Loudspeakers Daniel Beer, Fraunhofer Institute for Digital Media Technology - Ilmenau, Germany; Michaela Schuster, Michael Jahr, Technical University Ilmenau - Ilmenau, Germany; Alexander Reich, Fraunhofer Institute for Digital Media Technology - Ilmenau, Germany
Flat panel loudspeakers are characterized by their low manufactured depth. Compared with conventional loudspeakers the space saving integration in existing surroundings is an advantage. From the acoustics point of view disadvantages come along with the low manufactured depth that influence the reproduction in the lower and middle frequency range. Based on measurements and FEM-simulations the reasons for this behavior were analyzed. Supplementary methods for solving this problem have been considered that are derived from conventional loudspeaker technologies.
Convention Paper 7316 (Purchase now)

P1-4 The Inertial Air Load of a Loudspeaker Diaphragm John Vanderkooy, University of Waterloo - Waterloo, Ontario, Canada, and B&W Group Ltd., Steyning, West Sussex, UK
A typical bass loudspeaker driver has an inertial air load, which is about 30% of its actual cone mass. This air mass is often poorly understood, but it is significant in defining the resonance frequency; and the purpose of this paper is to understand the concept, clarify important aspects, and present corroborative measurements. The immediate surroundings of the diaphragm determine the low-frequency air load, and measurements on a test driver with different mountings arrangements are made and assessed, including measurements in vacuum. A loudspeaker box presents its own complications. Simulations are used to show how the air load depends on baffle size. In general, the air load may not be accurately represented by the usual approximations that apply to a piston in an infinite baffle or to a freely oscillating disk, but they do give a rough estimate.
Convention Paper 7317 (Purchase now)

P1-5 Horn Loudspeaker Nonlinearty Comparison and Linearization Using Volterra Series Delphine Bard, University of Lund - Lund, Sweden
The characterization of a weakly nonlinear electroacoustic device with usual methods of measurement (THD, intermodulation) does not illustrate the nonlinearities themselves, but only some of their effects. Device linearization can be achieved by applying the inverse nonlinearity upstream of the device, under the condition that the nonlinearity law is known in detail. This paper presents nonlinearities behavior comparison of horn loudspeakers of different frequency ranges using an experimental method of weak nonlinearity characterization and compensation, based on a representation of the nonlinearity by Volterra series using multitone excitations.
Convention Paper 7318 (Purchase now)

P1-6 Audibility of Phase Response Differences in a Stereo Playback System. Part I: Headphone Reproduction of Wide-Band Stimuli Geoff Martin, Sylvain Choisel, Bang & Olufsen A/S - Struer, Denmark
The audibility of phase distortion in sound reproduction systems has been the subject of many studies. However, it remains a topic of controversy, in particular in the field of loudspeaker or headphone equalization. Most studies lead to the conclusion that, although phase distortion may be audible for specific stimuli, in realistic listening situations in a room, they will go largely unnoticed. These studies, however, have focused on monophonic phase distortion; a severe limitation, since ignoring phase response in equalization can result in different phase distortion in different channels. It is the purpose of the present study to investigate the audibility of stereophonic phase mismatch in the specific case of headphone reproduction. In addition, the implications on microphone design and production are discussed.
Convention Paper 7319 (Purchase now)

Last Updated: 20080612, tendeloo