Patent Review: A Circular Shaped Planar Speaker System

The patent in review was granted in February 2015 to inventor Zhijun Zhao (West Bloomfield, MI) on behalf of Harman International Industries. As James Croft notes, planar magnetic transducers are often preferred for their thin form factor, ideal for shallow mounting spaces where a standard transducer may not fit, such as in-wall systems and automotive applications. The patent in review offers a practical solution for an oval or circular format planar magnetic transducer for such applications. This article was original published in Voice Coil, April 2015.

Following a recent exchange with loudspeaker designer and inventor John J. Gaudreault, we decided to revisit the very original Planar-Pivot (Planot) Transducer, and make available the two related articles that were published by Voice Coil in its May 2011 edition, and the respective Patent Review by James Croft published in the August edition of that same year. Hoping this will inspire some commercial implementations of this interesting concept, available for licensing.

In this edition of Voice Coil, Steve Temme explains "How to Measure Free-Field Speaker Response without an Anechoic Chamber," Mike Klasco writes about "Plastics and Composites for Audio Products in 2021," and there's an updated Speaker Enclosure Vendor Directory. James Croft provides a fascinating patent review of a speaker assembly design for low-frequency control using an acoustic dipole. And Vance Dickason characterizes two new tweeters: the D2404 Ellipticor Tweeter from Scan-Speak, and the Satori AT60NC-4 AMT Tweeter from SB Acoustics. Now available in print and online!

James Croft reviews two loudspeaker-related patents as a tribute to David John Graebener, who passed away on January 3, 2015. First James Croft reviews the planar-magnetic electro-acoustic transducer he patented together with Graebener, followed by a single-end planar magnetic speaker system, David’s key patent. These were the first and second of the Single-Ended, Neodymium planar magnetic transducer patents David Graebener was granted. This article was originally published in Voice Coil, March 2015.

The February 2021 edition of Voice Coil offers an overview of the Cone Industry in 2021, with an updated directory of loudspeaker cone, diaphragms and suppliers of relevant materials and components. Next up, James Croft reviews an interesting patent for a "Directional Loudspeaker," claimed by Dutch & Dutch BV, and Vance Dickason focuses his measurements on two small-sized drivers, typical of today's most popular consumer products. The first in Test Bench is the Wavecor FR070WA05, a 2.75" aluminum cone full-range driver, and the second is the AUGWL0006-JN01, a new 2.25" woofer from Eastech’s Punktkilde lineup.

This patent review looks at a “Loudspeaker with a Wave Guide” (Patent Number: US20140369543) by inventors Jussi Vaisanen and Ilpo Martikainen from Finish company Genelec. This patent relates to the Genelec 8351 Acoustically Coaxial Smart Active Monitor (SAM) monitor, originally launched in 2016. Later in 2017, Genelec expanded the concept into a complete series of Coaxial Active Monitors, “The Ones”. This article was originally published in Voice Coil, February 2015.

James Croft looks at an interesting new patent covering a “Compact Stand-Alone Stereo Loudspeaker” by inventor Jes Mosgaard from Libratone A/S (Denmark). This patent submitted in 2010, was granted in 2013, and describes a compact and portable stereo loudspeaker system that is capable of providing a spacious sound field using an internal stereo pair of loudspeakers arranged in a dipole configuration. This article was originally published in Voice Coil, February 2015.

Looking forward to serving the loudspeaker industry for another year, Voice Coil starts strong with a focus on Headphone OEM Devices and Parts, and a Spotlight article on speaker design, written by Brian Cho, the CEO of Resonado Labs. In his first Acoustic Patents column for 2021, James Croft writes about a signal processing system, allowing users to control a lower frequency acoustic range of a loudspeaker system, and Vance Dickason kicks off his Test Bench characterizations with the new Bold North Audio BWX-6502 Midbass, and the Wavecor TW022WA09 22mm textile dome tweeter.

James Croft reviews a patent claimed by Polk Audio and granted in 2015, describing “a single-enclosure loudspeaker system that projects multichannel surround sound into a listener’s room, and so replaces multiple conventional surround channel loudspeakers.” The patent also describes, in one embodiment of the invention, that the “surround channel program material is pre-processed by an integrated wireless transmission device that performs certain digital signal processing and channel mixing steps in advance of wireless surround signal broadcast to a receiver.” This article was originally published in Voice Coil, January 2015.

Every month on his Voice Coil's Acoustic Patents column, James Croft (Croft Acoustical) discusses different loudspeaker patents and inventions that are relevant to the audio industry. In the January 2015 edition. Croft reviewed a “Loudspeaker for Eliminating a Frequency Response Dip” patent, granted in November 12, 2014 to Harman International Industries, describing “a speaker system that includes a speaker enclosure having a front end, a rear end, and a first transducer. This article was originally published in Voice Coil, January 2015.