Happy 36th Anniversary Voice Coil! With the availability in print, digital, and online of the November 2022 issue of Voice Coil, we once again celebrate the launch of the periodical as an information resource for the loudspeaker industry. As Vance Dickason reminds us each year, the publication was born from a conversation with Ed Dell, about a dedicated information platform for the loudspeaker industry, which enthusiastically moved forward. Thirty-six years later, Voice Coil continues to play its fundamental role as "a world-class clearing-house of information for loudspeaker engineers, manufacturers, marketing specialists, and OEM suppliers."
For this month's issue, Mike Klasco (Menlo Scientific) - one of the earliest regular contributors to join Voice Coil - writes about "Enhancing Low-Frequency Performance" in the first part of a Focus article that this month explores how to generate More Bass. Based on his extensive experience as a loudspeaker industry consultant, Klasco explains what it means to "design for bass" and what innovations are available to increase low-frequency response while keeping the enclosure slim with higher acoustic output, overload protection, green design for reduced BOM, higher sensitivity, and even constraining bass leakage.
The article covers cutting-edge approaches, including the use of Klippel Sound Control (KSC) feed-forward speaker distortion nulling amplifier technology, negative output impedance to electrically synthesize Thiele-Small parameters, digital control loops with feedback, and even the promise of new compliance-enhancing mechanisms, as promised by Mayht's Heartmotion speaker, which inspired Sonos to acquire the Dutch startup for $100 million.
In direct complement of the topic, Mike Klasco offers a Directory of Bass-Enhancing Electronics Solutions, with the contact information for the technologies discussed in his focus article.
In his Acoustic Patents column, James Croft (Croft Acoustical) reviews US patent number 11,375,303, named "Near To the Ear Subwoofer," which was awarded to Mark William Ziemba (Livonia, MI) on behalf of Panasonic Corporation of North America. The recent patent, filed in January 25, 2021 and published June 28, 2022, discusses a loudspeaker arrangement for a seat within a motor vehicle with one or more localized sound output ports for low-frequency sound reproduction. The loudspeaker enclosure is situated below, behind, or in some fixed location around or within a vehicle seat, with the sound outputs ports situated at or near a headrest. This arrangement inspired James Croft to explore the approach and the potential advantages and drawbacks compared to prior art systems for automotive audio that are also conveyed to the headrest or directed at the vehicle occupants. Reference reading for automotive audio designers.
For this month's Test Bench, Vance Dickason characterizes a new professional audio coaxial driver from Italian manufacturer B&C Speakers. The 6CXN36 6.5" coincident coax transducer is fairly similar to the company's 5.25” 5CXN44 reviewed in Voice Coil, August 2021, which uses a nearly identical compression driver. The cooling for the 6CXN36 is exclusively provided by the motor mass, which is substantial given the large 80mm diameter (8mm thick) neodymium (neo) ring magnet that powers both the high-frequency and low-frequency units. No vents are required for the 200W continuous power handling rating given by B&C Speakers, which is impressive for a small diameter driver such as this.
Diaphragm materials for the 6CXN36 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. Driving the cone assembly is a 34mm (1.3") diameter voice coil with glass fiber former wound with round copper wire. The compression driver has a 36mm (1.4”) diameter voice coil wound on a Kapton former, but wound with aluminum wire. The short 90° aluminum conical shaped horn on the 6CXN36 makes it very suitable as a PA fill driver, or as a personal stage monitor.
The second Test Bench characterization in this issue of Voice Coil is for another very interesting full-range driver from Wavecor. The FR4X6WA01 is small oval diaphragm driver, built on a proprietary injection molded polymer four-spoke frame with the cone assembly consisting of a black anodized aluminum cone, with a 16mm diameter round black anodized aluminum dust cap. The black aluminum dust cap is directly coupled to the 16mm vented black non-conducting black fiberglass voice coil former, and suspended with a low loss (high Qm) NBR rubber surround and a 33mm diameter flat Conex spider (damper). Powering the cone assembly is a dual neodymium motor with a copper cap shorting ring and a milled return cup with black emissive coating. Tinsel leads connect on one side of the cone to a pair of solderable gold-plated terminals located on opposite sides of the frame, which discourages rocking modes.
To close the issue, there's another dose of Industry Watch topics, including a tribute to Billy Woodman, the founder of ATC Loudspeaker Technology (1946–2022).
This 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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