The Latest in Loudspeaker Knowledge and Developments in Voice Coil October 2023

In the October 2023 issue of Voice Coil, James Croft reviews an active noise control enclosure system, and Mike Klasco and Nora Wong provide an updated directory of Integrated Electronics for Loudspeakers. Vance Dickason offers three different driver characterizations, starting with the AMT100H driver from Eighteen Sound. Next up, he tests an updated version of the popular TW030WA23/24 tweeter from Wavecor. And finally, measures the Scan-Speak D2008/2010, the revised version of the classic dome tweeter from the Danish brand.

In this article, James Croft discusses a patent granted to Curtis Graber (Woodburn, IN) that describes a radial acoustic speaker assembly including a transducer and a plurality of segmented spiral horns acoustically coupled to the transducer, each with its acoustical path. This new patent by prolific audio inventor, Curtis Graber, uses a new multi-spiral waveguide structure driven by a single transducer and has clear advantages over prior art. This article was originally published in Voice Coil, May 2018.

This article discusses a patent originally claimed in 2013 on a Double Coil Speaker design, which was granted in 2017 to Friedrich Reining (Vienna, Austria), on behalf of Sound Solutions International. The abstract from the patent details an audio system comprising an electro-acoustic transducer having two stacked voice coils mechanically linked to a membrane. James Croft discusses multiple approaches in similar concepts, and notes that the current state of technology might finally create a way to explore it in commercial products. This article was originally published in Voice Coil, March 2018.

Renowned audio speaker design, David W. Gunness, now with Fulcrum Acoustic, and previously with Electro-Voice and Eastern Acoustic Works, is no stranger to this field of research where he holds numerous patents.This review is a fascinating read, especially given that Fulcrum has already proven the validity of the proposed designs in actual products. It seems clear that Gunness achieved “a very good design that should advance the art in the category of cardioid devices,” as Croft notes.

This article reviews two patents titled simply "Speaker Device" from four Japanese inventors, on behalf of Pioneer Corp. of Japan. The original and expanded patent describes a flat speaker device capable of emitting loud reproduced sound, using a mechanical structure that converts a linear voice coil motion in one axis to an orthogonal mechanical diaphragm displacement. The system functions much like a scissor-jack you would use to raise your automobile to change a tire. The linear motion of the threaded rod coverts the axial force to a 90° lift movement.

This patent, granted to MrSpeakers, the company from San Diego, CA that is now Dan Clark Audio, was granted in the same month that this review was published in Voice Coil. The patent details a headphone driver that should also be of note for the speaker industry. As Croft notes, the patent office initially rejected the claims due to prior patents, eventually accepting the inventor's arguments, in 2016. The review provides the historical context for planar magnetic transducers, and explains why this is an important patent.

This article examines a notable patent from VUE Audiotechnik, describing a loudspeaker system with one driver providing a direct radiating output from the front, and a second driver on a ported side chamber, sharing a ported common chamber, where at least one port of the ported common chamber exits the front of the loudspeaker system. As Croft notes, this is an innovative advanced system - that was patent-pending at the time - and provides a unique combination of technology, offering real-world advantages. The patent was granted in 2021.

This review highlights a patent granted to Bose Corp, part of an interesting series of bass reflex and tuned pipe enclosure architectures explored by Bose, which James Croft reviews and explains in detail. The patent describes a single chamber, single tuned, bass reflex enclosure system, using a more advanced, single Helmholtz tuned bass reflex design, with a port that is folded and extended. A great patent review with lots of informative details. This article was originally published in Voice Coil, October 2017.

Voice Coil June 2023 features an extensive patent review in James Croft's Acoustic Patents column. The topic is a 2014 patent awarded to Nokia, offering an opportunity to revisit the history of electrostatic loudspeakers, with insights from Tim Mellow, one of the two listed inventors. In Test Bench, Vance Dickason focuses on the D8404-552000 Ellipticor cloth diaphragm dome midrange from Scan-Speak, and characterizes the SB Acoustics TW29BNWG beryllium dome and waveguide from the brand's prestigious Satori line.

This review looks at a speaker patent, awarded to inventor Shengbo Li from Guangdong, China, on behalf of Harman International. The abstract from that patent details a speaker including one or multiple transducers, an enclosure, and a suspension mounted on the enclosure, wherein the suspension and the enclosure are configured such that the enclosure is capable of vibrating as a result of operation of the transducer so as to produce audible sound. You read it right, the enclosure is also a passive radiator!