For this issue of Voice Coil, Mike Klasco and Nora Wong (Menlo Scientific) have once again compiled a useful directory of headphone test and measurement instrumentation. In the introduction, they comment on the fact that this is an area where we continue to see a great deal of activity, both in software and hardware development. The trend to update systems to wideband artificial ear couplers and the development of increasingly more sophisticated designs continues to motivate additional investments in this segment.
In the June 2023 directory, Voice Coil readers will find a complete list of vendors supplying artificial ears, head-and-torso simulator (HATS) manikins, and related jigs and fixtures, as well as established solutions such as audio analyzers and end-of-line QC solutions.
For this issue's Acoustic Patents column, James Croft offers an inspired and extensive review of a patent awarded to Nokia in 2014 and listing Tim Mellow, (Great Britain) and M. J. Karkkainen (Finland) as the inventors. The title of the patent, "Apparatus with Directivity Pattern" would normally fail to generate the deserved attention from Voice Coil readers, but James Croft was quick to notice that this is in fact a planar radiator loudspeaker design with interesting characteristics. In fact, this patent has important implications to the field of electrostatic loudspeakers, an area that James Croft knows extremely well.
For Voice Coil readers, this is a unique - and extremely enjoyable - opportunity to learn about the detailed history of electrostatic loudspeakers, which is essential to understand the scope and motivations for the present invention, implemented in Mellow Acoustics' (Tim Mellow's company) FrontRo loudspeaker. The fact that this patent was assigned to Nokia, indicates interesting potential for applications in other fields, beyond home audio, listening room applications.
This issue of Voice Coil is particularly of note because of the two Test Bench articles from Vance Dickason. The first focuses on the D8404-552000 Ellipticor cloth diaphragm dome midrange from Scan-Speak. This is the sixth Scan-Speak Ellipticor driver to appear in Test Bench, a design that uses an oval (elliptical) voice coil shape to defeat cone and dome standing wave modes, enabling an "infinite" number of Eigen frequencies, but with less contribution for each frequency and overall lower distortion. Driving the diaphragm symmetrically also generates a finite number of Eigen frequencies with a higher contribution, combining at certain frequencies producing the coloration modes.
The Scan-Speak D8404 is a large dome midrange with a large diaphragm area and respective voice coil diameter. For a motor system, Scan-Speak basically scaled up its currently successful AirCirc tweeter motor with 12 neodymium slugs, with copper shorting rings and a titanium voice coil former, all part of the patented Symmetrical Drive SD-2 motor format. Other features include a coated-cloth elliptical dome, aluminum face plate, clear plastic back cover, gold-plated terminals, and the same very slick aluminum trim ring that covers the mounting screws of all Ellipticor drivers.
The second Test Bench characterizes the SB Acoustics TW29BNWG beryllium dome and waveguide from the brand's prestigious Satori line. As Vance Dickason underlines, Voice Coil has characterized several of these SB Acoustics tweeters, including ferrite and neodymium motor models with beryllium, cloth and TeXtreme TPCD domes. All these Satori transducers are developed by former Danish Vifa/Scan-Speak engineers Ulrik Schmidt and Frank Nielsen at Danesian Audio (www.danesian.dk). The new high-end 29mm beryllium diaphragm neodymium dome, the Satori TW29BNWG incorporates a 170mm (6.7") diameter aluminum waveguide, an 8mm wide coated cloth surround, a 29mm (1.14") beryllium diaphragm, dual copper caps on the T-shaped pole piece, dual balanced compression chambers, non-reflective optimally damped rear cavity, and CCAW round voice coil wire. A great evolution of the Satori TW29BN tweeter.
As always, in Industry Watch, Vance Dickason highlights some interesting industry announcements, new products and trends, this time detailing the SEAS Excel T29X and the Excel W19NX, the first with a TPCD Textreme cone and the second with a dome of the same material, new drivers from Celestion and Lavoce, as well as updates from the Audio & Loudspeaker Technology International (ALTI) Association, which is gearing up to its ALTI-EXPO , in Orlando, FL.
This issue of Voice Coil is available for download and already in the mail to print subscribers. Subscribers can go to - www.gotomyvcoil.com - to download this issue.
Remember, Voice Coil is available in print and download for all registered subscribers, free for industry professionals. To qualify for a free subscription to Voice Coil, or renew your subscription, go to: Voice Coil Subscriber Services.
To access the digital subscription platform, just login using your subscriber number and post/zip code as displayed on your mailing label.
