AES New York 2019
Engineering Brief EB5

EB5 - Transducers

Saturday, October 19, 9:00 am — 11:30 am

Alexander Voishvillo, JBL/Harman Professional Solutions - Northridge, CA, USA

EB5-1 The Application of Graphene Oxide-Based Loudspeaker Membranes in 40mm Headphone DriversWilliam Cardenas, ORA Graphine Audio Inc. - Montreal, Quebec, Canada; Robert-Eric Gaskell, McGill University - Montreal, QC, Canada
Graphene oxide-based materials have shown promise in loudspeaker membrane applications. The material allows the forming of highly stiff, low mass cones and domes for loudspeakers. The technology allows improvements in efficiency and linearity over other common loudspeaker membrane materials. This class of graphene material can be engineered to produce an excellent ratio of stiffness (Young’s modulus) to density (g/cm3) and damping (tan ? ). In a case study, acoustically optimized graphene materials were formed into membranes for headphone drivers. The performance of headphone drivers made with these membranes was analyzed and compared to standard polymer membrane headphone drivers. Relative to the polymer membrane drivers, the graphene membranes provide a significant reduction in both intermodulation and harmonic distortion while matching the sensitivity and producing a substantially smoother frequency response.
Engineering Brief 544

EB5-2 MEMS Loudspeakers - A New Chip-Based Technology for Ultra-Small SpeakersFabian Stoppel, Fraunhofer Institute for Silicon Technology ISIT - Itzehoe, Germany; Florian Niekiel, Fraunhofer Institute for Silicon Technology ISIT - Itzehoe, Germany; Andreas Männchen, Fraunhofer Institute for Digital Media Technology IDMT - Ilmenau, Germany; Daniel Beer, Fraunhofer Institute for Digital Media Technology IDMT - Ilmenau, Germany; Bernhard Wagner, Fraunhofer Institute for Silicon Technology ISIT - Itzehoe, Germany
Due to the ability to combine exceptional functionality with a very small size and a low price, micro-electro-mechanical systems (MEMS) have become the state-of-the-art solution for many miniaturized components like microphones and inertial sensors. Lately, strongly increasing efforts are being made to exploit the miniaturization potential and the advantages of semiconductor manufacturing processes to create ultra-small loudspeakers. In this context, a new technology for integrated chip speakers is presented. The MEMS speakers utilize multiple piezoelectric bending actuators, which are able to generate high sound pressure levels at low power consumption. Based on the results of an in-ear speaker system, an insight into the technology is given. Moreover, possibilities and challenges for MEMS speakers in general are discussed. [Presentation only; not available in E-Library]

EB5-3 A Case Study on a Dynamic Driver: How Electromagnet Can Improve the Performance of a Micro SpeakerMd Mehedi, Carpenter Technology Corporation - Philadelphia, PA, USA
How can designers improve the sound quality of next-generation audio products when the market is demanding smaller devices? Bigger sound requires bigger speakers, right? Not necessarily. One approach is to re-evaluate the materials you are using. Alloy materials used within speakers to conduct sound has not changed drastically in the last 10-15 years. However, developments in the performance of electromagnet alloys can replace standard electrical iron/low carbon steel and provide higher efficiency and performance. The result is better sound quality, smaller devices, and extended battery life. We studied the performance of the transducer with different electromagnets in magnet assembly and reported the comparison to provide better insight for the next-gen audio dynamic drives.
Engineering Brief 545

EB5-4 Alignment of Triple Chamber Eighth-Order Band-Pass Loudspeaker SystemsHao Dong, Nanjing University - Nanjing, China; Yong Shen, Nanjing University - Nanjing, Jiangsu Province, China; Rui Chen, Nanjing University - Nanjing, China
An eighth-order band-pass loudspeaker system consisting of three vented chambers is analyzed. Since its frequency response has equal low-pass and high-pass cut-off slopes of fourth-order, the response function can be aligned to an eighth-order symmetric band-pass filter obtained by the frequency transformation method. For any desired frequency response, required system alignment parameters can be calculated by solving a system of equations. Design examples are presented and compared in terms of the mid-band attenuation factor and the diaphragm displacement.
Engineering Brief 546

EB5-5 Analysis of a Vented-Box Loudspeaker System via the Impedance FunctionJames Lazar, Samsung Electronics - Valencia, CA, USA; Glenn S. Kubota, Samsung Research America - Valencia, CA, USA
The vented-box loudspeaker system is studied through a small-signal equivalent circuit model via the impedance function. Some traditional models are found to inadequately represent the system losses, lumping them together in an effort to simplify the design process. Here, a low-frequency small-signal equivalent circuit model is proposed, incorporating five loss elements. The impedance function is derived, and system parameters are determined by curve-fitting the impedance function to measured impedance data. It is shown that the reactive elements determine the critical frequencies, and the lossy elements determine the Q-factors or contribute to the impedance level. Moreover, the lossy elements affect the curve-fit in a unique way, allowing their values to be quantified.
Engineering Brief 547

EB5-6 Designing Listening Tests of SR/PA Systems, A Case StudyEddy Bøgh Brixen, EBB-consult - Smørum, Denmark; DPA Microphones - Allerød, Denmark
It is very common to arrange for comparisons of SR/PA-systems. However, often, these comparisons are organized in a way leaving procedures less transparent and results rather unclear. Standards for the assessment of loudspeakers do exist. The assessors basically must be trained for the purpose, and the set-up should support double-blind testing. However, in the test of big systems, the listening panel is not necessarily trained, and the practical problems of rigging huge arrays to some degree may weaken the procedures and the results. This paper describes considerations for the comparative assessment of SR/PA systems. The paper also reports the outcome of an experiment where considered principles were applied.
Engineering Brief 548

EB5-7 Noise and Distortion Mechanisms Encountered in Switching Audio Power Amplifier DesignRobert Muniz, Harmonic Power Conversion LLC - Doublas, MA, USA
When designing a switching power amplifier, many phenomena are encountered that leave the designer wondering why performance falls short of what theory predicts. While many sources of non-linearity and noise in the conversion process are known and intrinsic to the sub-systems involved, other sources of error are more subtle. The intent of this paper is to outline the noise, distortion, and error mechanisms commonly encountered in practice when designing a switching (Class-D) power amplifier. By understanding the root cause of these mechanisms, a more heuristic approach can be employed in switching power amplifier design. The focus will be on analog systems employing clocked, naturally sampled modulators, but the bulk of the material will be broadly applicable to any modulation scheme.
Engineering Brief 549

EB5-8 Acoustic Metamaterial in Loudspeaker Systems DesignLetizia Chisari, Contralto Audio srl - Casoli, Italy; Mario Di Cola, Contralto Audio srl - Casoli, Italy; Paolo Martignon, Contralto Audio srl - Casoli, Italy
Materials have been used to control waves propagation ever since, and optics is a prime example. In Loudspeaker Systems applications, there have also been approaches in the attempt of controlling waves by acoustic lenses. Metamaterials are artificial structures, typically periodic, composed of small meta-atoms that, in the bulk, behave like continuous material with unconventional effective properties without the constraints normally imposed by nature. This talk offers the opportunity to share what can be done with acoustic metamaterials in audio industry, especially in Loudspeaker Systems Design. The presentation brings back some approaches from the past that can be revisited using today’s technologies. Moreover, this talk shows some of the already developed technologies that employ these extremely innovative materials.
Engineering Brief 550

EB5-9 Application of Matrix Analysis for Derivation of Acoustical Impedance of HornsAlexander Voishvillo, JBL/Harman Professional Solutions - Northridge, CA, USA; Balázs Kákonyi, Harman Professional Solutions - Northridge, CA, USA; Brian McLaughlin, Harman Professional Solutions - Northridge, CA, USA
The direct measurement of a horn’s acoustical impedance requires knowledge of both the sound pressure and volume velocity at the throat of the horn. While measuring sound pressure is trivial, the measurement of volume velocity requires special equipment. This work proposes a new derivation method for the acoustical impedance of a horn. The method is based on matrix analysis and consists of two stages: derivation of the compression driver’s square transfer matrix of A-parameters, and measurement of electrical impedance and sound pressure at the throat of the horn. These functions yield two matrix equations that relate measured sound pressure and electrical impedance, which allows for an acoustical impedance derivation of the horn. A comparison with COMSOL simulation is provided.
Engineering Brief 551

EB5-10 Application of Modulated Musical Multitone Signal for Evaluation of Horn Driver Sound QualityAlexander Voishvillo, JBL/Harman Professional Solutions - Northridge, CA, USA; Balázs Kákonyi, Harman Professional Solutions - Northridge, CA, USA; Brian McLaughlin, Harman Professional Solutions - Northridge, CA, USA
This work introduces a new type of test signal called Modulated Musical Multitone (MMM): sinusoidal tones outlining E-minor triads in several octaves with amplitude modulation providing a variable crest factor which can match specific musical signals. Three different signals are used in the corresponding experiments including MMM, sinusoidal sweep, and music. An evaluation of sound quality is conducted for an FIR-filtered single horn driver. The effect of masking is observed when a matching linear low-pass channel is added to the signal. The multitone response is post-processed to obtain the distortion products spectrum.
Engineering Brief 552

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