Get Ahead on Cones, Woofers, Compression Drivers and More with Voice Coil February 2020!

January 27 2020, 17:00

For this edition of Voice Coil, Mike Klasco (Menlo Scientific, Ltd.) wrote the first part of an industry update on Speaker Cones. This Voice Coil Focus article explores the fabrication, materials, and performance aspects of this critical component in driver design. As Klasco writes in his introduction, "It is taken as a basic truth that most speaker factories can duplicate an existing design’s frame and magnetic structure, but getting the soft parts right is an art. The cone, surround, spider, and dust cap contain many of the secret ingredients in speaker design." With his extensive experience in dealing with innovative speaker designs and bringing concepts into production, Klasco details vital aspects of both paper pulp cone fabrication and polypropylene cones, addressing even the lesser known aspects, such as software simulation programs used to model results before starting tooling.

An ideal segue for this article is the comprehensive Directory of Loudspeaker Cone Industry Suppliers 2020, prepared by Nora Wong (Menlo Scientific, Ltd.). The scope of this year’s cone industry directory has been expanded to incorporate relevant material suppliers and component vendors such as specialized surrounds, spiders (dampers), and cone additives.

In his Acoustic Patents article, James Croft (Croft Acoustical) writes about an interesting "Self-Sealing Expandable Subwoofer," a recent patent awarded to Kenneth Harden, and assigned to BBY Solutions, Inc. (Best Buy) of Richfield, MN. This patent describes a subwoofer speaker assembly that has a housing that is convertible between a compact volume mode and an expanded volume mode, where the speaker assembly includes at least one driver contained within the housing. The housing itself comprises an internal frame and an external shell, moveable relative to the internal frame, allowing an expanded mode and greater volume. Positioned between the overlapping and parallel walls of the internal frame and the external shell is at least one sealing member, which provides an airtight seal between the internal frame and the external shell. As Croft comments, an interesting and novel aspect of this invention as compared to prior art is that the system includes a sensor that communicates with the amplifier to tell it what position, or expansion mode, the cabinet is in and adjusts the bass processing accordingly to optimize for the enclosure volume and the tuning frequency determined by the vent within the chosen enclosure volume. Read on.

For this month's Test Bench, Vance Dickason characterizes a new WAN103.01 10" woofer from Italian OEM transducer manufacturer, LaVoce. With manufacturing based in Jiashan, China (near Shanghai), all LaVoce products are designed at its headquarters in Potenza Picena, Italy, but with the logistic and price advantage of being manufactured at its purpose-built ISO 9001-certified production facility in China.

With a substantial feature set, WAN103.01’s applications are primarily as a midbass driver in multiway systems, combining a proprietary six-spoke cast-aluminum frame with enhanced voice coil cooling, combined with curvilinear waterproof coated paper cone and dust cap, and a motor design that utilizes a FEA-designed neodymium ring magnet structure and a 75 mm (3”) diameter voice coil wound with round copper-clad aluminum wire (CCAW) on a nonconducting Kapton former. The cast return cup includes a 0.9” diameter vent loading into a 1.5” diameter exhaust “tunnel.” Dickason clearly noted the excellent build quality, this being the first LaVoce piston range driver that he had the chance to characterize.

The next Test Bench explication focused on the 835PB ferrite 1.4” aluminum diaphragm compression driver, from Radian Audio Engineering, the company that was incorporated in 1988 by Dr. Richard Kontrimas and is now entering a new expansion phase under new ownership and having recently relocated to new facilities in Pomona, CA. After reviewing several of Radian’s neodymium series of compression drivers, Dickason now characterized one of Radian’s ferrite 1.4” aluminum diaphragm compression drivers and noted also how the 835PB continues to have the expected rich feature set that is the hallmark of the company.

Renowned for its mastery of diaphragms, compression drivers and coaxial loudspeakers, with the 835PB, Radian Audio shows how the company continues to offer excellent performance in a fairly high power handling package (200 W continuous power handing). Features for the 835PB 3" diaphragm, 1.4" exit, compression driver includes a 3” polyimide voice coil former with a copper clad aluminum edge wound ribbon wire voice coil, a self-aligning field replaceable diaphragm assembly, and the most important feature, a proprietary processed and hardened aerospace-grade aluminum alloy diaphragm over a three slit phase plug. The 835BP is also available with a beryllium diaphragm. Since Radian does not produce horns for its compression drivers, the measurements were made with a FaitalPro 1.4” LTH142 elliptical tractrix horn, which has a 60° × 50° coverage pattern and the same recommended crossover frequency of 800 Hz for the Radian 835BP.

The February 2020 edition of Voice Coil concludes with the traditional Industry Watch section.

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