Patent Review: Acoustic Transducer Comprising a Plurality of Coaxially Arranged Diaphragms

This is a review of a design patent, submitted on behalf of Tymphany, trying to address the shortcomings of the work of Dr. Oskar Heil with his Air Motion Transformer (AMT) woofer system. The patent describes an acoustic transducer comprising one or more electromagnetic motors that drive one or more sets of multiple diaphragms to provide acoustically efficient loudspeaker systems in compact dimensions.

This article reviews an intriguing new patent awarded to Turtle Beach Corp. addressing a new emitter circuit for providing a bias voltage, which is key for the development of electrostatic loudspeakers. Extremely aware of the techniques and historical perspective of the development in this area, Croft provides a complete overview of all the challenges, implications and merits of this patent and prior art. This article was originally published in Voice Coil, July 2018.

James Croft (Croft Acoustical) reviews a very curious patent from Amazon Technologies, Inc. (Reno, NV), filed in 2013, and awarded in April 2017. Basically, the patent discusses a new technique to tune a port of a loudspeaker, in this case multiple ports that will be open or selectively closed, in function of an analysis of the frequencies of the signal being played. This article was originally published in Voice Coil, June 2018.

James Croft looks at two patents from Resonado Labs, the young speaker company that has been pursuing a new speaker topology — originally called Flat Core Speaker (FCS), and now rebranded as Res-Core — using a reconfigured speaker with a planar voice coil mounted perpendicularly to its flat diaphragm. This review covers two of the company's patents granted in 2022, titled "Speaker Comprising Split Gap Plate Structure," and "Flat Speaker Driven by a Single Permanent Magnet and One or More Voice Coils.".

In this article James Croft reviews a patent claimed by Leeg Hyun Cho (Gyeonggi-do, Korea), Youngil Cho (Chicago, IL), and Christian Femrite (Westminster, CO) on behalf of Resonado. The patent in question will be familiar to many Voice Coil and audioXpress readers who have followed the news about this young company's developments. As an experienced patent reviewer and speaker technology expert, Croft adds valuable context to the awarded patent. This article was originally published in Voice Coil, July 2021

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.