This first issue of Voice Coil for 2024 includes an article written by Patrick Turnmire, the founder and principal of Redrock Acoustics, renowned for offering engineering and design services and which recently reopened access to its Klippel testing and transducer analysis services. Turnmire has tested thousands of driver samples during his career, including countless for Voice Coil's Test Bench. In a rare appearance as a writer, Turnmire talks about "Diagnosing Design Issues Using the Klippel Distortion Analyzer."In Industry News & Developments, Vance Dickason visits Audio Precision’s headquarters in Beaverton, OR, where he meets with Dan Knighten, AP's Product Line General Manager, to talk about the recently announced Audio Precision APx516 Analyzer.
In this month's Acoustic Patents column, James Croft (Croft Acoustical) addresses a patent filed in 2019 and recently awarded to Eduardo Mendes and Bérenger Roig on behalf of French manufacturer Devialet. Titled "Infinite Baffle with Low Stiffness" this is in fact an attempt to reduce internal enclosure volume while maintaining or improving bass extension and efficiency by way of harnessing the negative-spring principle. A very familiar concept that James Croft has extensively reviewed over the last 15 years or so — the acoustical equivalent of achieving a "perpetual motion machine." Devialet is an interesting company that pushes the envelope when it comes to offering "power" from a compact loudspeaker. Have they found the formula?
Next up, Voice Coil features an updated directory of 2024 Earphone and Headphone Manufacturers. For this year's updated listings, Nora Wong (Menlo Scientific) compiled many of the leading OEM/ODM headphone and earphone factories, which are recognized and available to supply the industry. This is followed by a dedicated directory of Headphone and Earphone Parts, listing suppliers of acoustic resistance woven and non-woven parts, diaphragms, and headphone drivers.
Finally, in Test Bench, Vance Dickason characterizes the new DE350-8 Ultra-Compact 1" Compression Driver from B&C Speakers. This ultra-compact (under 60mm diameter) driver was measured along with the B&C Speakers ME10v2 90°x60° coverage horn. In terms of features, the DE350-8 is designed for use with 1" throat horns and incorporates a 1.4" high temperature Polymer diaphragm driven by a 36mm (1.4") diameter voice coil, and a neodymium inside slug magnet. But the really cool feature is the patent-pending phase plug. Inside, the DE350 has a round symmetrical outside channel, and an inside channel with a patent-pending twist for overall improved frequency response. Weighing in at a mere 275 gram, it is an ideal candidate for the new generation of lighter, more compact line array loudspeakers.
The second driver for Test Bench is the eagerly awaited characterization of the new LM10n Wide Band Ribbon Transducer from Radian Audio Engineering. One of the most interesting drivers launched in 2023, it is recognized for its great sounding compression and coax drivers, Radian's latest planar transducers were designed by 35-year loudspeaker engineering veteran Igor Levitsky, with the LM10n being the latest and larger sized model (approximately 255mm (10”) x 116mm (4.6”)) of this recently updated series.
The LM10n is described as a wide range 120Hz to 20kHz ribbon planar transducer, which excels as a midrange when combined with a smaller ribbon device such as the Radian LT2 or LT3. Features for the LM10n include a FEA-optimized symmetric push-pull neodymium magnet motor structure, an advanced polymer diaphragm, thermally conductive polymer frames, constant directivity in the horizontal plane, and a continuous power handling of 70W AES with a 200W short-term IEC power handing. As Levitsky recommends, the LM10n can be utilized in both open-back (dipole) and closed-back (monopole) formats.
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