Patent Review: Bose Transmission Line Loudspeaker

In this Voice Coil Acoustic Patents article, James Croft discusses an interesting Transmission Line Loudspeaker patent assigned to three engineers from Bose regarding an electro-acoustic driver and acoustic waveguide that includes “an enclosure, an acoustic transmission line formed within the enclosure, and a plurality of acoustic transducers contained within the enclosure and disposed along a length of the acoustic transmission line.” As Croft notes, this seems to be an improvement over the Tapped Horn loudspeaker architecture patented by Tom Danley, assigned 10 years ago. This article was originally published in Voice Coil, June 2015

Voice Coil July 2021 is now available and full of valuable articles. Starting with Mike Klasco's insights on glue joints and attachment techniques used in speaker design. Followed by an updated and comprehensive directory of manufacturers and suppliers of adhesives, coatings, and treatments for the speaker industry. James Croft reviews the recent Bidirectional Speaker patent awarded to Resonado Labs, and Vance Dickason places the totally unique Purifi PTT6.5X04-NFA-01 midbass driver on Test Bench, followed by Beyma's 12LEX1300Nd 12” woofer with its unique Maltcross cooling system. Now available in print and online!

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.