120th AES Convention - Paris, France - Dates: Saturday May 20 - Tuesday May 23, 2006 - Porte de Versailles

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AES Paris 2006

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Last Updated: 20060404, mei

P19 - Loudspeakers and Sound Reinforcement

Monday, May 22, 14:00 — 18:20

Chair: Andrew Goldberg, Genelec Oy - Iisalmi, Finland

P19-1 On the Influence of the Geometry on Radiation for Electrodynamic LoudspeakersNicolas Quáegebeur, Antoine Chaigne, ENSTA - Palaiseau Cedex, France
The basic conception of loudspeakers has remained unchanged for decades. In particular, the shape of the diaphragm is nowadays designed as the association of a spherical cap and a truncated cone. The present paper focuses on the influence of the shape of the diaphragm on the sound radiation. A temporal model based on spatial impulse response has been developed to predict the sound radiation of an axisymetrical source subjected to an impulse. It is shown that nonplanar sources are less subject to off-axis amplitude and phase variations than planar sources. The comparison between convex and concave geometries is also studied. It is shown that transients are more accurately reproduced by convex structures.

Presentation is scheduled to begin at 14:00
Convention Paper 6775 (Purchase now)

P19-2 Methods to Improve the Horizontal Pattern of a Line Array Module in the MidrangeNils Benjamin Schröder, Tobias Schwalbe, Robert Mores, Hamburg University of Applied Sciences - Hamburg, Germany
This paper reviews methods for modeling the vertical directivity of the frequency range from 200 Hz to 1 kHz in line array configurations. It describes the advantages and disadvantages of the following concepts: the horn, the “V-Alignment,“ the flat alignment, and the partial coverage of the loudspeakers. We will shed light on the interrelationship between the angle of two cone loudspeakers and the resulting directivity. Symmetrical and asymmetrical configurations of mid-range drivers and horns are compared. We will outline a procedure to combine these solutions for superior results. One main result will be the desired match of the midsection’s directivity with the directivity of the hf-waveguide section. A concept for building systems with variable directivity over the whole frequency range will be drafted.

[Associated Poster Presentation in Session P26, Tuesday, May 23, at 09:00]

Presentation is scheduled to begin at 14:20
Convention Paper 6776 (Purchase now)

P19-3 The Performance and Restrictions of High Frequency Waveguides in Line ArraysNils Benjamin Schröeder, Tobias Schwalbe, Robert Mores, Hamburg University of Applied Sciences - Hamburg, Germany
It is necessary to form a plane coherent wavefront in the hf-section of line arrays. Several different concepts have been applied to reach this goal. We discuss these existing solutions. The different ideas on how to create a cylindrical wavefront will be explained and evaluated. Especially those waveguides that have their weak point in the theoretical design will be criticized. An explanation on how we developed a new waveguide will be given. Finally, we want to give some ideas on how the next generation of waveguides could be designed.

[Associated Poster Presentation in Session P26, Tuesday, May 23, at 09:00]

Presentation is scheduled to begin at 14:40
Convention Paper 6777 (Purchase now)

P19-4 Efficient Nonlinear LoudspeakersBo Rohde Pedersen, University of Aalborg - Aalborg, Denmark; Finn T. Agerkvist, Technical University of Denmark - Kgs. Lyngby, Denmark
Loudspeakers have traditionally been designed to be as linear as possible. However, as techniques for compensating nonlinearities are emerging, it becomes possible to use other design criteria. This paper presents and examines a new idea for improving the efficiency of loudspeakers at high levels by changing the voice coil layout. This deliberate nonlinear design has the benefit that a smaller amplifier can be used, which, in turn, has the benefit of reducing system cost as well as reducing power consumption.

[Associated Poster Presentation in Session P26, Tuesday, May 23, at 09:00]

Presentation is scheduled to begin at 15:00
Convention Paper 6778 (Purchase now)

P19-5 Advantages of FIR Filters in Digital Loudspeaker ControllersGuenter J. Krauss, Telex Communications Inc., EVI Audio GmbH - Straubing, Germany
Finite Impulse Response (FIR) filters for real-time audio applications can today be realized comparably easy and cost-effectively with state-of-the-art DSP technology. FIR filters have real advantages over regular Infinite Impulse Response (IIR) filters in loudspeaker controllers with regard to straight-forward linear-phase component equalization and significant improvements in the radiation pattern of cabinets with noncoincident drivers.

Presentation is scheduled to begin at 15:20
Convention Paper 6779 (Purchase now)

P19-6 Efficient Resonant Loudspeakers with Large Form-Factor Design FreedomRonald M. Aarts, Joris A. M. Nieuwendijk; Okke Ouweltjes, Philips Research - Eindhoven, The Netherlands
Small cabinet loudspeakers with a flat response are quite inefficient. Assuming that the frequency response can be manipulated electronically, systems that have a nonflat SPL-response can provide greater usable efficiency. Such a nonflat design can deal with very compact housing, but, for small drivers, it would require a relatively large cone excursion to obtain a high SPL. However, mounting the driver in a pipe, the air column can be made to resonate, which enables the use of small drivers with a small cone excursion to obtain a high SPL. For these special loudspeakers, a practically relevant optimality criterion, involving the driver and pipe parameters, will be defined. This can be especially valuable in designing very compact loudspeaker systems. An experimental example of such a design is described and a working prototype is presented.

Presentation is scheduled to begin at 15:40
Convention Paper 6780 (Purchase now)

P19-7 A Dipole Multimedia LoudspeakerVladimir Filevski, Broadcasting Council of Macedonia - Skopje, Macedonia
A multimedia/computer loudspeaker usually stands on a desk, so the reflected sound from the desk interferes with the direct sound from the loudspeaker. This results in a comb-like frequency response, with first minimum deep at least -8 dB, followed higher in the frequency by a peak of about +4 dB, and so on. This paper describes the design of a dipole multimedia/computer loudspeaker, with less than +2 dB/ -2.4 dB of difference between resultant frequency response (including reflected sound from the desk) and anechoic response.

[Associated Poster Presentation in Session P26, Tuesday, May 23, at 09:00]

Presentation is scheduled to begin at 16:00
Convention Paper 6781 (Purchase now)

P19-8 Spatial Distribution of Distortion and Spectrally-Shaped Quantization Noise in Digital Micro-Array LoudspeakersMalcolm Hawksford, University of Essex - Essex, UK
A concept for a digital loudspeaker array is studied composed of clusters of micro-radiating elements that form individual digital-to-acoustic converters. In this scheme a large-scale array is composed of subgroups of micro clusters. To accommodate the finite resolution of each cluster, noise shaping is proposed and parallels are drawn with the processes used in digital-to-analog converters. Various elemental array geometries for each micro cluster are investigated by mapping transduction output into 3-D space to reveal the spatial distribution of both noise and distortion that result from noncoincident and quantized digital-to-acoustic elements.

Presentation is scheduled to begin at 16:20
Convention Paper 6782 (Purchase now)

P19-9 A Compact 120 Independent Element Spherical Loudspeaker Array with Programmable Radiation PatternsRimas Avizienis, Adrian Freed, Peter Kassakian, David Wessel, University of California at Berkely - Berkeley, CA, USA
We describe the geometric and engineering design challenges that were overcome to create a new compact, 10-inch
diameter spherical loudspeaker array with integrated class-D amplifiers and a 120-independent channel digital audio interface using Gigabit Ethernet. A special hybrid geometry is used that combines the maximal symmetry of a triangular-faceted icosahedron with the compact planar packing of six circles on an equilateral triangle ("billiard ball packing"). Six custom 1.25-inch drivers developed by Meyer Sound Labs are mounted on each of 20 aluminum triangular circuit boards. Class D amplifiers for the six loudspeakers are mounted on the other side of each board. Two pentagonal circuit boards in the icosahedron employ Xilinx Spartan 3E FPGA's to demultiplex digital audio signals from incoming Gigabit Ethernet packets and process them before feeding the class-D modulators. Processing includes scaling, delaying, filtering, and limiting.

[Associated Poster Presentation in Session P26, Tuesday, May 23, at 09:00]

Presentation is scheduled to begin at 16:40
Convention Paper 6783 (Purchase now)

P19-10 Polar Plots at Low Frequencies: The Acoustic CenterJohn Vanderkooy, University of Waterloo - Waterloo, Ontario, Canada; David J. Henwood, B & W Group Limited - Steyning, West Sussex, UK
This paper studies some aspects of how polar plots should be carried out when measuring loudspeakers. At low frequencies the effect of the cabinet becomes simpler as the wavelength of the sound becomes large relative to the cabinet dimensions. This allows a particular point to be picked out that acoustically acts as the center of the loudspeaker at the lower frequencies. This concept is verified by acoustic simulation, and also theoretically by expressing the source radiation into a multipole expansion. Some general criteria are presented to give estimates of the acoustic center for different geometrical aspects of the cabinet. Polar plots pivoted about the acoustic center display very consistent low-frequency characteristics. The discussion includes a number of other considerations regarding the acoustic center.

Presentation is scheduled to begin at 17:00
Convention Paper 6784 (Purchase now)

P19-11 Constant Directivity End-Fire Arrays for Public Address SystemsFilip Verbinnen, University of Southampton - Southampton, UK
The directivity of current public address systems is controlled very well in mid and high audio frequencies using arrays or horns. Low frequencies, though, are mostly still omnidirectional. The cardioid subwoofer is making its introduction but has some drawbacks limiting the maximum sound pressure level achievable by this type of system. As a possibly better alternative, the end-fire line array is considered as a directive bass system. Some research has already been done on end-fire arrays but none exploited the current potential of digital signal processing techniques. Using a linear end-fire array of loudspeakers each with its own digitally-processed input, the possibilities and limitations of these tapered end-fire linear arrays were examined with the main goal to create a constant directivity end-fire array with a usable frequency range from 20Hz to 200 Hz.

[Associated Poster Presentation in Session P26, Tuesday, May 23, at 09:00]

Presentation is scheduled to begin at 17:20
Convention Paper 6785 (Purchase now)

P19-12 DGRC Arrays: A Synthesis of Geometrical and Electronic Loudspeaker ArraysXavier Meynial, Active Audio - St. Herblain, France
Loudspeaker arrays offer an efficient way of achieving both uniform SPL coverage and high sound clarity over a large audience area. Two types of arrays have been proposed over the last 15 years: geometrically steered J shape arrays, mainly for high power sound reinforcement; and electronically steered vertical arrays, mainly for speech diffusion in public spaces. This paper introduces the Digital and Geometric Radiation Control (DGRC) principle, which combines the advantages of geometrical arrays and electronic arrays; an array that is vertical so that it can be mounted on a wall; that is controlled with great flexibility using its DSP; and that the power is evenly distributed upon loudspeakers.

[Associated Poster Presentation in Session P26, Tuesday, May 23, at 09:00]

Presentation is scheduled to begin at 17:40
Convention Paper 6786 (Purchase now)

P19-13 Universal System for Spatial Sound Reinforcement in Theaters and Large Venues—System Design and User InterfaceFrank Melchior, Gabriel Gatzsche, Michael Strauss, Katrin Reichelt, Martin Dausel, Joachim Deguara, Fraunhofer IDMT - Ilmenau, Germany
Sound reinforcement for large venues is a challenging task. Up to now most of the systems and concepts are focused on a more or less stereophonic reproduction. Beside these concepts a promising technology exists, which enables a spatial sound reinforcement for a larger audience. Spatial sound reinforcement is an important aspect especially in high quality applications like opera houses and venues for classical music. This paper presents an innovative system- and multi-user interface concept for dynamic automation and interactive control of sound source positions and other properties for variable reproduction systems in live sound reinforcement applications. The system has been designed in close cooperation with experts in sound reinforcement for opera houses. The developed user interfaces are described in addition to a detailed view on the practical realization and audio processing in such a system.

[Associated Poster Presentation in Session P28, Tuesday, May 23, at 09:00]

Presentation is scheduled to begin at 18:00
Convention Paper 6787 (Purchase now)

  (C) 2006, Audio Engineering Society, Inc.