In Industry News & Developments Vance Dickason discusses the problems of detection of audible resonances in transducers and loudspeaker systems. As highlighted in a paper on the subject that was published in September 2007, “Detection of Audible Resonances,” by Ivo Mateljan (the author of ARTA analyzer software), Heinrich Weber, and Ante Doric, by measuring the energy of the resonance - and not just resonance level and Q-factor - the authors have determined the actual influence of resonances on the frequency response and group delay. The interesting conclusions provide a completely different perspective than standard cumulative spectral decay (CSD) plots and burst decay waterfall plots, which provide a more accurate depiction of the listeners' actual perception and make those measurements easier to read. As Vance notes, this doesn't completely invalidate CSD plots (originally popularized by the MLSSA analyzer), but we need to be aware of the bias the technique imposes and this work highlights the fact that there is a more realistic way to view resonances at different frequencies.For this December 2022 issue of Voice Coil, Mike Klasco (Menlo Scientific) offers the second part of his article about ways to Enhance Low-Frequency Performance and obtain Even More Bass. Following an overview of smart amplifier speaker overload protection with distortion canceling, amplifier control of the loudspeaker’s Thiele-Small (T-S) parameters through motional feedback, and feedback network integrated circuits optimized for sensor servo control of speaker drivers, all offered in Part 1 of this valuable article, Part 2 offers an update of other less known techniques, starting with Servo Feedback, where a speaker voice coil or diaphragm position sensor is used to reduce distortion and extend bass response. Specific examples of companies and solutions include SubVo, DSP solutions such as Waves' MaxxBass, passive cardioid speaker designs, and the innovative and novel approach from Dinaburg Technology, among others.
As scheduled for this issue, Nora Wong compiled an updated directory of Measurement Microphones vendors, an always essential tool for loudspeaker designers, installation professionals, sound reinforcement engineers, and acousticians. From ACO Pacific to GRAS, Hottinger Bruel & Kjaer (HBK), iSEMcon, and PCB Piezotronics, all the companies providing or applying measurement microphones are listed for our readers' convenience.
For this edition of Test Bench, Vance received two of the latest products to come out of the R&D labs of Acustica Beyma, the Spanish pro sound OEM transducer manufacturer, which celebrated 50 years in 2019 and has introduced some significant proprietary technologies in its transducers. The company continues to expand its R&D team, with results now visible in a new set of transducers that crossover from pure professional audio applications into the studio and high end world. Specifically, Vance characterizes two models from Beyma's new Near and Mid Field (NMF) series, all introduced in 2022, and which continue that innovation tradition.
Beyma sent the first two tweeters in the NMF series, the T-25M aluminum/magnesium alloy metal dome tweeter, and the T-25S silk dome tweeter. Both of these new tweeters share a similar feature set.
First in Test Bench is the T-25M NFM 1” dome tweeter, which features a reinforced black anodized aluminum/magnesium diaphragm with a large wide polymer-based surround, a CCAW voice coil wound on an vented aluminum former, a FEA-designed ferrite magnet sandwiched between a cast T-yoke, and a polished CNC’d front plate with shaped cavity areas below the diaphragm. The vented pole piece is fitted with a copper cap plus three types of damping material: dense felt on the pole surface, open-cell foam in the pole vent, and felt behind the vent in the rear cavity. The rear cavity is cast aluminum and is constructed so that it screws to the back of the aluminum front plate holding the entire assembly together rather than the magnet assembly being screwed from the front, like the majority of tweeters in the industry. This results in a particularly clean-looking front plate cosmetic appearance. Specifications detail a 20W AES power handling, recommended crossover frequency of 2.5kHz (with a 12dB/octave high-pass filter), and 88dB at 2.83V/1m sensitivity.
Next in Test Bench is the Beyma T-25S 1" silk dome tweeter, with a feature set that is nearly identical to the T-25M, with the exception of the polymer-impregnated silk dome and wide 6mm polymer based surround. Specifications detail 15W AES power handling, and a 92dB at 2.83V/1m sensitivity.
As usual, this issue of Voice Coil wraps up with a generous dose of Industry Watch news updates, which also mention the latest drivers launched in the market, new updates from test and measurement companies, and update from the Audio & Loudspeaker Technologies International (ALTI) Association, which is hosting its first ALTI CES Hospitality Suite in Lido 3101B on the third floor of the Venetian Convention Center. A B2B space that will be mandatory for any loudspeaker professionals and speaker companies attending CES 2023. The ALTI Suite at CES 2023 is supported directly by audioXpress and Voice Coil magazines, and visitors will be able to pick up the latest issues at the reception desk.
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