Patent Review: Two Single-Ended Planar-Magnetic Speaker Patents

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.

In its August 2020 edition, Voice Coil featured an article by experienced speaker designer Igor Levitsky, highly recognized in the industry for developing some of the best planar magnetic speaker and headphone drivers for some of the most reputed brands, focusing precisely on this type of technology. It seems clear that we will see more and more headphones and speakers using thin-film drivers, as the industry is now perfecting the use of different types of diaphragms and materials. The August 2020 edition of Voice Coil includes the first part of this article, completed in the September 2020 edition.

The September edition of audioXpress is our always popular Speaker Builder - Speaker Focus edition. Once again, audioXpress focuses on loudspeaker building, design, and testing and for this issue we have combined two great DIY articles with a review of the PureAudioProject Trio15 Heil AMT speaker system. Ward Maas reports from the High End 2019 show in Munich, Jan Didden met with Purifi Audio's Bruno Putzeys and Lars Risbo and comments on the company's research, and much more.

In January and February 2001, audioXPress included a project from Thomas Perazella, describing in detail the design and construction of a speaker using the Bohlender Graebener RD-75 planar magnetic driver. This is the second part of the project, detailing the final part of the speaker construction, measurements and listening trials.

In January 2001, the first audioXPress magazine issue (Vol. 32 No.1) included this project from Thomas Perazella. Published in two parts, the articles described in detail the design and construction of a speaker using the Bohlender Graebener RD-75 planar magnetic driver, including references to previous experiments with dipole baffles. This is the first part of the project.