In this edition’s Industry News & Developments section, Vance Dickason explains why speaker and acoustic engineers need to pay attention to the latest APx500 software updates from Audio Precision (AP). The Oregon-based audio test company has added new measurement results, options, and test signals to establish its APx500 software as a reference solution for production testing of loudspeakers, headphone drivers, and microphones. Most importantly for the designers and manufacturers of speaker drivers, and products incorporating them, the software now offers the broadest set of methodologies available for detecting rub and buzz defects. Dickason looks in detail at the new detection methods, new stimulus signals and all the new features.
And this month's Voice Coil Spotlight makes way for Bruno Putzeys and Lars Risbo, co-founders of Purifi Audio, to share some details about the company's unique research with loudspeakers. In "Some Speaker Problems That Needed Solving," Putzeys and Risbo reveal their findings in looking for the roots of speaker nonlinearities and distortion mechanisms. These were in fact the efforts that led to the fundamental design used in Purifi's growing line of drivers, featuring many innovations including Force Factor Modulation (FFM) -optimized motors and Sd-neutral cone surround using alternating normal and inverse roll segments. A research effort that the authors believe deserves consideration from the industry, as a new set of standard parameters that should be included in datasheets.
This edition of Voice Coil also focuses on the vital coil winding business. In an updated 2021 directory of Global Voice Coil Winders and Converters, Nora Wong (Menlo Scientific) offers an overview of an industry that continues to persevere through rough times. As most North American speaker manufacturing has moved south of the border or to the Far East during the last two decades, it is even more important to understand the winding companies. The updated directory characterizes who these suppliers are, where they are located, and their specialties.
Complementing the directory on Voice Coil vendors, this August 2021 edition also includes an updated directory of Magnet Vendors and Distributors, compiled by Mike Klasco and Nora Wong (Menlo Scientific). Knowing that a comprehensive directory of magnet, plates, forgers, and material vendors would be the size on a phonebook, the two industry specialists filtered recognized vendors for the speaker industry.
In this month Acoustic Patents column, James Croft (Croft Acoustical) looks at a Grill-Integrated Low-Pass Filter and Speaker (Patent/Publication Number: US 2021/0185444), assigned to Bujeon Co., Ltd., with multiple inventors listed. This patent, granted in June 2021, covers a tubular-type low-pass filter conduit formed inside the speaker housing, designed to attenuate the higher frequencies of a subwoofer, woofer, or midrange. This acoustic approach, as Croft notes, can provide the benefit of attenuating the harmonic distortion, and can be configured to optimize a directivity waveguide for a secondary driver, or increase dispersion, or even to attenuate a narrow band resonance in more complex designs. Being the noted inventor of acoustic filters of this type, Croft is able to offer an expanded overview of prior-art and the unique benefits and desirable attributes of the multiple approaches, and specifically the patent now awarded to Bujeon.
For this month's edition of Test Bench, Vance Dickason received a new coaxial 5.25” driver from B&C Speakers. As Dickason notes, coaxial transducers are a growing, important category for professional audio and even home applications, and yet not many drivers of this type are submitted to Test Bench. In this article, he characterizes B&C Speakers' 5CXN44 model, a woofer/compression driver combo specifically built primarily for sound reinforcement applications. This driver is built on an eight-spoke (four twin spokes) cast-aluminum frame, with cooling exclusively provided by the motor mass, a substantial neodymium ring magnet that powers both high-frequency and low-frequency units. No other vents are required for the 300W power rating given by B&C Speakers to the 5CXN44, which is impressive. Diaphragm materials for the 5CXN44 include a curvilinear paper cone with a front-side waterproof coating for the woofer, and a High Temperature (HT) Polymer for the compression driver diaphragm. The woofer is driven by a 1.7" diameter voice coil with a Kapton former wound with round copper wire. The compression driver has a 1.4" diameter voice coil also with a Kapton former, but wound with aluminum wire. This HT Polymer diaphragm fires into a short aluminum conical-shaped horn, which brings the sensitivity to 101dB, with a recommended crossover frequency of 2kHz.
And, this month's Industry Watch pays tribute to DIY audio pioneer and author David B. Weems (1922-2021), known by many in the speaker design and building community for his prolific authorship of DIY books.
The August 2021 edition 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: audioxpress.com/page/Voice-Coil-Subscriber-Services.html
Access to Digital Subscriptions
The pandemic has affected everyone’s lives, including those who provide our delivery service. With a surge in delivery demands and travel restrictions, we realize some of you may be experiencing significant delays in receiving your magazines. So KCK Media opened up its digital subscription platform to all print subscribers for no additional fee. To access it, just login using your subscriber number and post/zip code as displayed on your mailing label.
