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.

The March 2015 edition of Voice Coil is now available online and in print. Vance Dickason reviews the ALMA International Winter Symposium 2015. Test Bench discusses the 12NDL88 from B&C Speakers. Mike Klasco does a roundup of Test & Measurement companies from the Nordic region. Voice Coil pays tribute to David John Graebener (1948-2015).

For our March 2015 edition, we have selected a series of articles dedicated to Test & Measurement, both from a practical and a DIY perspective. First is Ethan Winer’s (re)take on Practical Applications for SPL Meters, followed by an historical recap from Voice Coil magazine editor Vance Dickason, on his reputed Test Bench process used to characterize drivers. We also discuss Headphone Testing issues among other things.