AES New York 2013
Paper Session P14

P14 - Transducers—Part 2: Headphones and Loudspeakers

Saturday, October 19, 2:30 pm — 6:00 pm (Room 1E07)

Christopher Struck, CJS Labs - San Francisco, CA, USA

P14-1 Application of Matrix Analysis to Identification of Mechanical and Acoustical Parameters of Compression DriversAlexander Voishvillo, JBL/Harman Professional - Northridge, CA, USA
In previous work of the author special measurement methods were used to obtain the transfer matrices of compression drivers. This data was coupled with the results of the FEA simulations of horns. It made it possible to simulate the frequency amplitude and directivity responses of horn drivers without building actual physical horns. In this work, a different set of measurements is used to obtain the transfer matrix of a vibrating diaphragm. This approach results in a more detailed and flexible method to analyze and design compression drivers. Other parameters used in the identification process are the electrical parameters of the motor and the acoustical parameters of compression chamber and phasing plug. The method was used in design and optimization of the new JBL dual-diaphragm compression driver to be used in a new JBL line array system.
Convention Paper 8988 (Purchase now)

P14-2 Application of Static and Dynamic Magnetic Finite Elements Analysis to Design and Optimization of Transducers Moving Coil MotorsAlexander Voishvillo, JBL/Harman Professional - Northridge, CA, USA; Felix Kochendörfer, JBL/Harman Professional - Northridge, CA USA
Transducer motors are potential source of nonlinear distortion. There are several nonlinear mechanisms that generate nonlinear distortion in motors. Typical loudspeaker nonlinear models include the dependence of the Bl-product and the voice coil inductance Lvc on the voice coil position and current. These effects cause nonlinearity in the driving force, electrodynamic damping, and generate nonlinear flux modulation and reluctance force. In reality, the voice coil inductance and resistive losses depend also on frequency. To take these effects into account the so-called LR-2 impedance model is used. The L2 and R2 elements are nonlinear functions of the voice coil position and current. In this work detailed analysis of a nonlinear model incorporating these elements is performed. The developed approach is illustrated by the FEA-based design and optimization of a new JBL ultra-linear transducer to be used in a new line array system.
Convention Paper 8989 (Purchase now)

P14-3 End-of-Line Test Concepts to Achieve and Maintain Yield and Quality in High Volume Loudspeaker ProductionGregor Schmidle, NTi Audio AG - Schaan, Liechtenstein
Managing high volume, multiple line, and location loudspeaker production is a challenging task that requires interdisciplinary skills. This paper offers concepts for designing and maintaining end-of-line test systems that help to achieve and maintain consistent yield and quality. Topics covered include acoustic and electric test parameter selection, mechanical test jig design, limit finding strategies, fault-tolerant workflow creation, test system calibration and environmental influence handling as well as utilizing statistics and statistic process control.
Convention Paper 8990 (Purchase now)

P14-4 Advances in Impedance Measurement of Loudspeakers and HeadphonesSteve Temme, Listen, Inc. - Boston, MA, USA; Tony Scott, Octave Labs, LLC - Eastchester, NY, USA
Impedance measurement is often the sole electrical measurement in a battery of QC tests on loudspeakers and headphones. Two test methods are commonly used—single channel and dual channel. Dual Channel measurement offers greater accuracy as both the voltage across the speaker (or headphone) and the reference resistor are measured to calculate the impedance. Single Channel measurement methods are more commonly used on the production line because it only requires one channel of a stereo soundcard, which leaves the other free for simultaneous acoustic tests. They are less accurate, however, due to the test methods making assumptions of constant voltage or constant current. In this paper we discuss a novel electrical circuit that offers similar impedance measurement accuracy compared to complex dual channel measurement methods but using just one channel. This is expected to become popular for high throughput production line measurements where only one channel is available as the second channel of the typical soundcard is being used for simultaneous acoustic tests.
Convention Paper 8991 (Purchase now)

P14-5 Auralization of Signal Distortion in Audio Systems—Part 1: Generic ModelingWolfgang Klippel, Klippel GmbH - Dresden, Germany
Auralization techniques are developed for generating a virtual output signal of an audio system where the different kinds of signal distortion are separately enhanced or attenuated to evaluate the impact on sound quality by systematic listening or perceptive modeling. The generation of linear, regular nonlinear and irregular nonlinear distortion components is discussed to select suitable models and measurements for the auralization of each component. New methods are presented for the auralization of irregular distortion generated by defects (e.g., rub & buzz) where no physical models are available. The auralization of signal distortion is a powerful tool for defining the target performance of an audio product in marketing, developing products at optimal performance-cost ratio and for ensuring sufficient quality in manufacturing.
Convention Paper 8992 (Purchase now)

P14-6 Free Plus Diffuse Sound Field Target Earphone Response Derived from Classical Room Acoustics TheoryChristopher Struck, CJS Labs - San Francisco, CA, USA
The typical standardized free or diffuse field reference or target earphone responses in general represent boundary conditions rather than a realistic listening situation. Therefore a model using classical room acoustics is introduced to derive a more realistic target earphone response in a direct plus diffuse sound field. The insertion gain concept as applied to earphone response measurements using an ear simulator equipped test manikin is detailed in order to appropriately apply the model output to a typical earphone design. Data for multiple sound sources, multiple rooms, and variants of the direct 0° on-axis free field response are shown. Limits of the method are discussed and the results are compared to the well-known free and diffuse field responses.
Convention Paper 8993 (Purchase now)

P14-7 Listener Preferences for In-Room Loudspeaker and Headphone Target ResponsesSean Olive, Harman International - Northridge, CA, USA; Todd Welti, Harman International - Northridge, CA, USA; Elisabeth McMullin, Harman International - Northridge, CA USA
Based on preference, listeners adjusted the relative bass and treble levels of three music programs reproduced through a high quality stereo loudspeaker system equalized to a flat in-room target response. The same task was repeated using a high quality circumaural headphone equalized to match the flat in-room loudspeaker response as measured at the eardrum reference point (DRP). The results show that listeners on average preferred an in-room loudspeaker target response that had 2 dB more bass and treble compared to the preferred headphone target response. There were significant variations in the preferred bass and treble levels due to differences in individual taste and listener training.
Convention Paper 8994 (Purchase now)

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