Full-Range Loudspeaker Industry Coverage in Voice Coil April 2021

In this April 2021 edition of Voice Coil, we are proud to offer an outstanding Spotlight feature. "Practical Considerations for Quality Control Testing of Loudspeakers" is an article written by Daniel Knighten and Eric Hodges detailing how the latest Audio Precision APx517B acoustic analyzer, developed specifically with the manufacturing environment in mind, can be conveniently and efficiently adapted for different test strategies. Integrating a power amplifier, microphone power supply, and analyzer required for speaker tests, the article details how the APx517B can save time in the overall test process through reduced setup and configuration steps. The authors also explain how this new AP solution meets the need to balance the cost of test including time, test methods, and system cost, against "the cost of failure" that might result from the expense of warranty repairs, or the possible negative impact to brand from product returns. Read this article for valuable insights on manufacturing test considerations and applied strategies for efficient testing.

Also for this diversified edition, Mike Klasco and Nora Wong (Menlo Scientific) have prepared a new report on Audio Cables and Connectors, an area that continues to show an important pace of innovation by both the leading vendors and completely new companies. As the report expands, "within the speaker driver there is the voice coil leadout flex wire to the terminals. On the speaker enclosures, there are also the terminals (or audio connectors on amplified speakers), along with the internal wiring harnesses between speakers, amplifiers, crossovers, and the speaker system input or I/O panel. For designers of headphones and earphones, cables and connectors are a consideration for comfort, microphonic noise pickup, and reliability; and for passive speakers, there many cables and connectors between the amplifiers and the speakers."

This Voice Coil Focus article highlights some of the more interesting developments and innovations in this space, spanning from JackSavior, the startup that introduced a more robust connector for standard audio connections, to Hua Cheng, which is now manufacturing the unique Roboden elastic stretch wire under license from Asahi Kasei, and Danish industry leader and litz wire pioneer Estron, which just created the new T2 Dual Spring Connector System, the next-generation connector system for small personal audio devices, hybrid hearables, and in-ear monitors.

This Focus article is complemented with an updated directory of Cable and Connector Vendors of interest to the speaker industry.

In his Acoustic Patents column, James Croft (Croft Acoustical) explores the fascinating details of a recent "Multi-Baric Low Frequency Sound Transduction Loudspeaker with Rectified Ultrasonic-to-Audio Pressure Amplitude Modulation Conversion." A long name for a patent recently awarded to a Brazilian company from Sao Paulo. The result of an extensive academic research that only an experienced loudspeaker technology and patent expert could fully explore, the invention describes a revolutionary low-frequency woofer system employing a variable amplitude, ultrasonic transducer, operating at a fixed carrier frequency. This is complemented by a rotational multi-opening disc that is placed in front of the transducer, spinning at a synchronized rate of the carrier frequency. Read it to fully understand the implications of this ultrasonic subwoofer invention to the industry.

For the "pièce de resistance," in Test Bench, Vance Dickason has been measuring two recently introduced high frequency drivers from two well respected European manufacturers, Eighteen Sound from Italy, and Acustica Beyma, from Spain.

The first product on Test Bench is Eighteen Sound’s recent ND1TP Compression Driver and XT120 Horn. Already the result of the company's recent efforts in the aftermath of the Eighteen Sound (and Ciare) acquisition by B&C Speaker in 2018, this is the first review of a new Eighteen Sound driver since that transition. The company continues as a discrete brand separate from B&C, and they sent Voice Coil one of its latest 1" compression driver designs, the ND1TP, along with its XT120 elliptical-shaped 1" horn. The ultra-compact ND1TP compression driver has a 25mm (1") throat diameter driven by a 44mm (1.75") diameter edge-wound voice coil wound with copper-clad aluminum wire (CCAW) on a non-conducting Nomex former with a proprietary treatment. This specially treated Nomex former shows a 30% higher value of tensile elongation at operating temperatures (200° C) when compared to Kapton. This assembly drives the titanium diaphragm and PEN surround. The ND1TP also incorporates a proprietary phase plug design that has short openings and a high flare rate that, according to the company, reduces distortion and improves mid-range detail. The drivers features a computer-optimized neodymium magnet motor structure and is rated for a continuous power handling of 100W and 50W nominal power handling, with a 1.6kHz recommended crossover frequency. Along with the ND1TP, Eighteen Sound provided the 1" XT120 90° x 60° elliptical horn with a 1.5kHz cut-off frequency. Made from high-pressure injection-molded polyurethane foam, the XT120 has a smooth flare rate that provides constant directivity from 2.5kHz.

The second product in Test Bench is the recently released CD-11Nd compression driver and TD-194 horn from pro sound OEM, Acustica Beyma. Designed for use with 1" throat horns, the CD-11Nd has a 25.4mm (1") throat diameter driven by a 44.4mm (1.75") diameter voice coil wound both inside and outside of a non-conduction Kapton-type former with aluminum wire. The diaphragm and surround are composed of a single piece of PM4, which is a proprietary high-tech polymer that, according to the company, has never before been used for audio. The CD-11Nd also incorporates a cast-aluminum cover with a black emissive coating on the cover and the plates. Other features include a FEA-optimized neodymium magnet motor structure, a program power handling of 140W with a 70W AES power handling rating, a 1.5kHz recommended crossover frequency, and 1W/1m 111dB sensitivity (measured on a Beyma TD-164 horn). The TD-194 horn has a 90° × 40° coverage pattern and is made from cast aluminum. For ease of mounting, the horn is square and the horizontal and vertical orientation is molded into the outer edge.

This edition concludes as usual with a balanced dose of Industry Watch updates, where Vance Dickason pays tribute to the memory of audio industry pioneer and legend Rupert Neve (July 31, 1926 – February 12, 2021).

The April 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.

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