Transducers

Friday, October 20, 4:30 pm — 5:45 pm (Rm 1E11)

Chair:
Pascal Brunet, Samsung Research America - Valencia, CA USA; Audio Group - Digital Media Solutions

EB04-1 The Resonant Tuning Factor: A New Measure for Quantifying the Setup and Tuning of Cylindrical Drums—Rob Toulson, University of Westminster - London, UK
A single circular drumhead produces complex and in-harmonic vibration characteristics. However, with cylindrical drums, which have two drumheads coupled by a mass of air, it is possible to manipulate the harmonic relationships through changing the tension of the resonant drumhead. The modal ratio between the fundamental and the batter head overtone therefore provides a unique and quantified characteristic of the drum tuning setup, which has been termed as the Resonant Tuning Factor (RTF). It may be valuable, for example, for percussionists to manipulate the RTF value to a perfect musical fifth, or to simply enable a repeatable tuning setup. This research therefore considers a number of user interfaces for analyzing the RTF and providing a tool for quantitative drum tuning. 

EB04-2 Design and Implementation of a Practical Long-Throw High-Q CBT Array—D. B. (Don) Keele, Jr., DBK Associates and Labs - Bloomington, IN, USA; Marshall Kay, Keysight Technologies - Apex, NC, USA
This paper describes the design and construction of a very-tall 5m experimental passive long-throw high-Q CBT array that provides coverage in a large church general-purpose activity room with a full-size basketball court. The room is 7.8 x 20 x 30 m (H x W x L). The 5 m tall 20° circular- arc array contains 80 ea 63.5 mm (2.5”) full-range drivers, and provides a tight 15° vertical beamwidth. The mechanically aimed no-DSP passive segmented design is composed of five straight-front boxes each containing 16 drivers. Series-parallel connections, resistive attenuators, and two power amplifiers provide the frequency-independent four-bank CBT shading. This paper also provides detailed simulation data of the array’s predicted beamwidth vs. frequency, directivity, vertical polar response, axial foot prints and predicted frequency response at three different downward tilt angles. The array provides very-even coverage along the entire length of the 30 m room. 

EB04-3 Effects of Acoustic Center Position in Subwoofers—Mario Di Cola, Audio Labs Systems - Casoli, Italy; Paolo Martignon, Contralto Audio srl - Parma (PR), Italy; Merlijn van Veen, Merlijn van Veen - Soest, Utrecht, The Netherlands
As explained by J.Vanderkooy [1] the acoustic center of a direct radiating subwoofer unit is placed ahead respect to the driver membrane, at a distance depending on driver and cabinet dimensions. This has effects on acoustic simulations and it deserves some attention to avoid errors. Measurements are shown which confirm acoustic center position theoretical calculation and a discussion is made about its effect on the definition of models for accurate simulations. 

EB04-4 Design and Implementation of a Constant-Directivity Two-Way 12” Woofer Wedge Loudspeaker System—D. B. (Don) Keele, Jr., DBK Associates and Labs - Bloomington, IN, USA; Hugh Sarvis, Presonus Audio Electronics-Worx Audio Technologies - Baton Rouge, LA, USA
This paper describes the design and implementation of a two-way constant-directivity wedge loudspeaker system that houses a single 12” woofer and eight 2” drivers in a 20° circular arc mounted on a curved baffle that covers the LF driver. An individual system comprises a 20° wedge box with a four-channel plate amplifier with two bridged channels driving the woofer, and the two other channels individually driving each half of the eight-driver array. This basic wedge box is then used in multiples to form larger circular-arc arrays of one up to six boxes making arrays that provide various vertical beamwidths in the range of 15° to 90°. Appropriate amplifier gains are chosen to smooth the polar coverage for each array size. 

EB04-5 A Tutorial on the Audibility of Loudspeaker Distortion at Bass Frequencies—James Larson, Audioholics—Online A/V Magazine - South Elgin, IL, USA; Gene DellaSaia, Audioholics—Online A/V Magazine; D. B. (Don) Keele, Jr., DBK Associates and Labs - Bloomington, IN, USA
This tutorial paper goes into detail concerning the audibility and perception of loudspeaker distortion at low frequencies. It draws on many past references and publications to summarize many of the factors that contribute to low-frequency loudspeaker distortion. Items covered include: “What is distortion and how do we perceive it?,” causes of distortion, types of distortion and audibility: linear vs. nonlinear, THD vs. IM vs. intermodulation distortion etc., auditory masking and distortion thresholds, measurement methods including continuous sine wave, two-tone IM, tone-burst, and multi-tone log-spaced testing among others. In conclusion, this paper observes that distortion does occur, but by identifying the point at which distortion becomes audible, one can be prudent in choosing which distortions to ignore.