The June 2022 Issue of Voice Coil provides a good dose of all the things that make this publication an essential resource for the loudspeaker industry. Starting with a useful overview by Vance Dickason of the Multi-Tone Measurement Module (MTON) available for the Klippel KA3 Analyzer in Industry News & Developments. While Voice Coil’s Test Bench reviews only make use of the Large Signal Identification (LSI) data from the Klippel Analyzer, the reality is that there are 30 modules available for the KA3 that are seriously valuable for transducer and system development. And Vance Dickason regularly discusses a number of these modules in Voice Coil. The MTON module is a Klippel RnD module, which provides a complete measurement of the device under test (DUT) using a multi-tone stimulus, delivering, among other things, valid mechanical and thermal compression limits, or SPL measurements according to IEC and ANSI standards.
As Voice Coil does every year, this June edition contains an updated Directory of Headphone Test & Measurement Equipment, compiled by Mike Klasco and Nora Wong (Menlo Scientific). In this 2022 updated resource, the two industry experts looked at the evolution of audio test & measurement instrumentation and the latest trends and players in headphones, both in software and hardware development. As headphones continues to be a fast-growing category, the requirements for artificial ears, HATS manikins, and related jigs and fixtures, as well as new approaches for system design and architecture are also evolving. In this directory, our readers will find full company and product range characterizations of companies, including Audio Precision, Audix, Austrian Audio, CRY Sound, GRAS Sound & Vibration, HEAD acoustics, Hottinger Bruel & Kjaer, Klippel, Warkwyn Larson Davis/PCB Piezotronics, Listen, Loudsoft, miniDSP, Parts Express, and Zumi Systems.
In this issue's Acoustic Patents, we revisit James Croft's column archives to rediscover a "Loudspeaker With Internal Negative Stiffness Mechanism" patent, filed in 2004, and granted in 2008, to inventor Shuji Saiki, on behalf of Panasonic Corp. (Japan). This is an interesting review to re-read, since it explores the implications of a loudspeaker device, where the interior space of a cabinet is divided in two chambers, featuring two ring-shaped fixed magnets on two diaphragms, where vibration of the diaphragms vibrated by sound pressure from each speaker unit is intensified by forces of attraction of the magnets in order to reduce an acoustic stiffness of the cabinet and equivalently increase a cabinet volume. The goal is to improve bass reproduction in a smaller cabinet. Sounds interesting? Well, that patent has expired. Read to learn more.
Next up, Vance Dickson serves another generous dose of his Test Bench characterizations, starting with the latest Celestion CDX1-1412 Compression Driver, a compact 1” unit intended for professional audio applications, and a traditional segment for the UK-based OEM manufacturer. This driver is the latest member of Celestion's extensive CDX line of neodymium (neo) motor compression drivers, totaling 12 models at this time. This compression driver as has a 25mm (1”) throat diameter driven by a 34mm (1.4) diameter voice coil wound with round copper clad aluminum wire (CCAW) on a nonconducting former driving a single piece polyimide diaphragm and surround. Other features include a FEA-optimized neodymium ring magnet motor structure, a nominal power handling of 35W with a 70W continuous power handling rating, a 2kHz recommended crossover frequency (with a minimum 12dB/octave high-pass network), and 106dB sensitivity (1W/1m measured on a typical horn), and a two bolt M5 mounting configuration. Along with the CDX1-1412, Celestion supplied its new 1" H1-9050 90°x50° constant directivity horn.
Next in Test Bench is an interesting recent 3" dome midrange from Tang Band Speaker (aka TB Speaker), model 75-1558SH, intended for high-end and home audio applications. Tang Band is increasingly recognized as one of the most innovative and prolific OEM speaker manufacturers from Asia, and the company once again submitted a unique and creative transducer design. The unit sent to Voice Coil is a new 75mm diameter soft dome midrange, using a coated cloth diaphragm and surround, a 75.5mm diameter voice coil wound with round copper wire on a black anodized vented aluminum voice coil former with magnetic fluid in the gap area. The motor system on this model 75-1558SH consists of large neodymium slug magnet with a low carbon content steel return cup with a black emissive coating that also incorporates a distortion reducing shorting ring. The steel cup has a foam damped vent that loads into a shaped and 100% polyester-filled injection-molded back enclosure. The driver is rated for 25W power handling (200W on program material) with nominal 8Ω impedance, with 90dB 1W/1m sensitivity.
This June 2022 issue of Voice Coil also features the valuable Industry Watch section, detailing the latest on Sonos $100 million acquisition of Mayht Holding BV, a Netherlands-based company that has invented a new, revolutionary approach to audio transducers, Perlisten Audio appointing Erik Wiederholtz as the company’s new chief technical officer (CTO), and the publications of the new AES75 Standard for Loudspeaker Measurement, which is already being praised by the industry. Also discussed is HEAD acoustics' latest Multi-Dimensional Audio Quality Score (MDAQS) tool and method for audio quality assessment. This important development is the world’s first binaural perception-based software tool that replaces human evaluation with novel metrics in the audio device development process.
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