AES San Francisco 2010
Paper Session P7

P7 - Loudspeaker Design and Amplifiers

Friday, November 5, 9:00 am — 1:00 pm (Room 236)

Christopher Struck

P7-1 An Improved Beryllium Dome Diaphragm Assembly for Large Format Compression DriversMarshall Buck, Psychotechnology, Inc. - Los Angeles, CA, USA; Gordon Simmons, Sam Saye, Brush-Wellman - Fremont, CA, USA
We describe the development, manufacture, and testing of a new large format compression driver diaphragm using a beryllium dome and new type of polymer surround that exhibits improved performance. This design promises to give long life and good reliability with little or no change in performance anticipated over the life of the diaphragm. A comprehensive set of tests of Beryllium, Aluminum, and Titanium diaphragm compression drivers is described including frequency response, distortion, and wavelet time domain analysis on a 2-inch plane wave tube. Substantial differences were measured in the performance categories, particularly in the frequency range above 4 kHz.
Convention Paper 8190 (Purchase now)

P7-2 Point-Source Loudspeaker Reversely-Attached Acoustic Horn: Improvement of Acoustic Characteristics and Application to Some MeasurementsTakahiro Miura, Teruo Muraoka, Tohru Ifukube, The University of Tokyo - Tokyo, Japan
It is ideal to measure acoustic characteristics by point- source sound. We proposed, at a previous convention, a point-source measurement loudspeaker that is designed to attach the mouse of hyperbolic horn to the diaphragm of the driver unit. The difference of directional intensity of the loudspeaker at the frequency range of 20 – 700 Hz were within 3 dB at any combination of azimuth and elevation. At the frequency range over 700 Hz, differences of azimuthal directional intensity were within 10 dB while that of the elevational ones were within 20 dB. Following these results, difference of directional frequency characteristics is discussed. Then we applied the loudspeaker for the measurement of acoustic characteristics of a hall.
Convention Paper 8191 (Purchase now)

P7-3 Ironless Motor Loudspeaker: Quantization of the Subjective Enhanced Sound QualityMathias Remy, Technocentre Renault - Guyancourt, France, Laboratoire d'Acoustique de l'Université du Maine, Le Mans Cedex, France; Guy Lemarquand, Technocentre Renault - Guyancourt, France; Daniele Ceruti, Faital S.p.A., Fabbrica Italiana Altoparlanti S.p.A. - Donato Milanese (MI), Italy; Gaël Guyader, Laboratoire d'Acoustique de l'Université du Maine - Le Mans Cedex, France; Romolo Toppi, Faital S.p.A., Fabbrica Italiana Altoparlanti S.p.A. - Donato Milanese (MI), Italy; Marc-François Six, Hutchinson S.A. - Chalette-sur-Loing Cedex, France
This paper presents a set of measurements realized on two automotive loudspeakers. These two loudspeakers have the exact same moving part and suspensions parts but different motors. The first one is equipped with a traditional production model motor made of ferrite and iron whereas the second one gets a prototype of ironless motor made totally of permanent magnets. Blind listening tests performed with these two loudspeakers showed a significant advantage of perceived sound quality for the ironless motor loudspeaker. Several types of measurements have been realized in order to try to quantify and explain this sound quality enhancement. Results are given in this paper.
Convention Paper 8192 (Purchase now)

P7-4 Air Velocity and Pressure Profiles in the Front of an Electrodynamic LoudspeakerDanijel Djurek, Allesandro Volta Applied Ceramics (AVAC) Laboratory for Nonlinear Dynamics - Zlatar Bistrica, Croatia; Ivan Djurek, Antonio Petosic, University of Zagreb - Zagreb, Croatia
Air velocity was recorded in front of an electrodynamic loudspeaker by the use of hot wire anemometric technique. Wire temperature response was detected up to 2 kHz and harmonics were analyzed by the use of the King formula. Near field effects were detected at the z-axis distances comparable to the loudspeaker diameter. Extended Greenspan theory was applied to explain measured data. It was stressed the importance of air viscosity in damping of Morse convection in near field regime. Near field effects at distances up to 30 cm were discussed in terms of the Morse convection indicated by the imaginary part of air impedance. According to continuity equation of air flow microphone signal was correlated to the fluid velocity divergence.
Convention Paper 8193 (Purchase now)

P7-5 New Techniques for Evaluating Audio Amplifiers via Measuring for Induced Wow and Flutter and Differential Phase DistortionsRon Quan, Ron Quan Designs - Cupertino, CA, USA
In the past, mechanical systems were measured for Wow and Flutter or frequency modulation but not amplifiers. Instead, amplifiers are typically measured for intermodulation and harmonic distortion. A new method for audio amplifier/device performance measures frequency modulation effects and differential phase distortion. Frequency and phase detectors are used to evaluate induced frequency and phase modulation from an amplifier under two conditions. The first condition has a low frequency signal inducing the modulation on a high frequency signal. The second condition has a high frequency AM signal inducing the modulation on a lower frequency signal. Practical design topologies for the new test methods are shown and the results of the new testing methods are tabulated.
Convention Paper 8194 (Purchase now)

P7-6 Analysis of Two-Pole Compensation in Linear Audio AmplifiersHarry Dymond, Phil Mellor, University of Bristol - Bristol, UK
An analysis of the two-pole compensation technique used in three-stage linear audio amplifiers is presented. An expression for the loop-gain of a linear amplifier incorporating two-pole compensation is derived, allowing the designer to easily select the unity loop-gain frequency and zero location by choosing appropriate values for the compensation components. Also presented is a simulation method that allows the designer to observe an amplifier’s closed-loop and loop-gain responses in a single pass without requiring modification to the circuit’s feedback path; and two separate modifications to the usual two-pole compensation approach that improve phase margin and significantly enhance negative-rail power-supply rejection ratio.
Convention Paper 8195 (Purchase now)

P7-7 A Robust Pseudo-Ternary Modulation Scheme for Filter-Less Digital Class D AmplifiersRossella Bassoli, Carlo Crippa, Germano Nicollini, ST-Ericsson - Monza Brianza, Italy
This paper presents a new pseudo-ternary modulation scheme for bridge-tied-load digital class D amplifiers that is more robust versus output stage distortions compared to existing ternary modulations. The effects of finite rise and fall times and their mismatches have been introduced for a classical ternary modulation scheme, where a large degradation of the dynamic range can be observed and then extended to reported high performance ternary modulators. It is shown that, even if linearization pulses are inserted to cope with the finite rise/fall time problem, also these modulators are somehow impacted by the edge mismatches.
Convention Paper 8196 (Purchase now)

P7-8 Switching/Linear Hybrid Audio Power Amplifiers for Domestic Applications, Part 1: The Class-B•D AmplifierHarry Dymond, Phil Mellor, University of Bristol - Bristol, UK
The analysis, design, and testing of a parallel switching/linear hybrid audio power amplifier rated at 100 W into 8 ohms are presented. The amplifier employs a hysteretically controlled switching stage and high-bandwidth linear amplifier whose high-gain negative-feedback loop controls the output signal. The majority of the output current is provided by the switching stage, enhancing efficiency. The amplifier’s fidelity has been tested with standard commercially available equipment, while efficiency has been evaluated across a very wide range of signal and load conditions using a custom active-load and automated test procedure. The combined fidelity and efficiency test results are analyzed, and the suitability for domestic applications of this amplifier configuration discussed.
Convention Paper 8197 (Purchase now)

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