Authors: Davy, Manuel; Doncarli, Christian
Loudspeaker fault detection is a difficult industrial problem for both manufacturing fault detection and maintenance. A new brief (<100-ms), nonstationary test signal aimed at detecting acoustic loudspeaker faults is presented. This signal is composed of four simultaneous chirp components and contains all the frequencies in the loudspeaker frequency range. The signal processing technique used to process the recorded loudspeaker responses is based on optimized time frequency representations (TFRs). The TFR corresponding to a given loudspeaker is compared to a reference TFR using a time frequency distance measure. The efficiency of the proposed test procedure, as well as its practical interest, are shown with real data.
Authors: Omoto, Akira; Hiratsuka, Chizuko; Fujita, Hiroaki; Fukushima, Tetsuhiko; Nakahara, Masataka; Fujiwara, Kyoji
Most of the recent numerical simulations in room acoustics focus on estimating impulse responses. However, the accuracy of the calculated impulse response may be called into question. This problem can be regarded as the difficulty in judging the similarities of sound fields based on impulse responses. The aim of the present study is to examine the possibility of a calculable parameter that assesses the similarities of sound fields. Fundamental to the discussion are the relationships among the following four items: 1) similarities of appearance of the impulse response waveforms, 2) various calculable parameters that may support the visual impressions, 3) various physical parameters, such as C and EDT, and 4) similarities of sounds generated by the convolution of impulse responses with a dry source.
Authors: Leach, Jr., W. Marshall
When the series resistance is separated and treated as a separate element, it is shown that losses in an inductor require the ratio of the flux to MMF in the core to be frequency dependent. For small-signal operation, this dependence leads to a circuit model composed of a lossless inductor and a resistor in parallel, both of which are frequency dependent. Mathematical expressions for these elements are derived under the assumption that the ratio of core flux to MMF varies as wn - 21, where n is a constant. A linear regression technique is described for extracting the model parameters from measured data. Experimental data are presented to justify the model for the lossy inductance of a loudspeaker voice coil. A SPICE example is presented to illustrate the effects of voice-coil inductor losses on the frequency response of a typical driver.
Authors: Button, Douglas J.
Although the electrodynamic drive topology incorporating two axially (not concentrically) placed coils is not a new idea and dates back to the 1950s, recent interest in the design has started a proliferation of the design conception professional and consumer markets. The fundamental design involves two coils that are opposite in phase and reside in oppositely polarized magnetic gaps, thus providing a Lorentz force in the same axial direction. The two gaps are formed from the same magnetic circuit, and both coils are wound on the same form, separated by some distance, connected or wound out of phase, and attached to a single diaphragm. Different design options with magnetic materials, magnetic circuit geometries, and voice-coil topologies are described. The focus is on performance tradeoffs and advantages in weight, power handling, power compression, and distortion relative to a single-gap design.
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