Patent Review: Acoustic Resistive Elements for Ported Transducer Enclosure

This review highlights a patent granted to Bose Corp, part of an interesting series of bass reflex and tuned pipe enclosure architectures explored by Bose, which James Croft reviews and explains in detail. The patent describes a single chamber, single tuned, bass reflex enclosure system, using a more advanced, single Helmholtz tuned bass reflex design, with a port that is folded and extended. A great patent review with lots of informative details. This article was originally published in Voice Coil, October 2017.

This review looks at a speaker patent, awarded to inventor Shengbo Li from Guangdong, China, on behalf of Harman International. The abstract from that patent details a speaker including one or multiple transducers, an enclosure, and a suspension mounted on the enclosure, wherein the suspension and the enclosure are configured such that the enclosure is capable of vibrating as a result of operation of the transducer so as to produce audible sound. You read it right, the enclosure is also a passive radiator!

This patent awarded to inventor Matthias Larrieu, on behalf of French company NEXO (owned by Yamaha Corp.) was the topic of this detailed review by James Croft. From the abstract it might be difficult to visualize what exactly differentiates the patented design from a standard bass reflex system. Basically, Larrieu created two V-shaped slices at the opening either centered or with one at each side of the port, helping to reduce amplitude and phase anomalies in the midrange due to port resonances, while improving mid-band directivity.

This article examines an important patent filed in 2014 by F. Bruce Thigpen (Tallahassee, FL) and granted in June 2016. Appearing both as the inventor and assignee, Thigpen describes a rotary sound transducer having an improved output at higher frequencies. Thigpen has been working on this type of device for more than a decade and has advanced what was already a very difficult engineering achievement, to a more sophisticated structure that apparently raises the general performance and high frequency limits beyond what was thought possible with this architecture. This article was originally published in Voice Coil, July 2017.

This review addresses an important patent awarded to Joseph F. Pinkerton (Austin, TX), on behalf of Clean Energy Labs, LLC. The patent describes an audio speaker having one or more passive radiators, and more specifically, an audio speaker having a passive radiator with dynamically adjustable resonant frequency. Croft reviews the patent and compares it with previous attempts to achieve this useful development, with significant potential if its full capability is realized.

This article analyzes a patent awarded in March 2017 to Yeh-Feng Chou (Taiwan), on behalf of Meiloon Industrial Co., Ltd., of a new Passive Radiator Structure, which adds some desirable attributes and improved performance. As the abstract details, the passive radiator structure includes a surround suspension, a frame, and a web-like spider having a plurality of suspension arms integrally extended to between the diaphragm and the frame, which together minimize sound distortion, increase compliance and upgrade efficiency.

This review looks at a patent awarded in October 2016 to George Bullimore, on behalf of Tymphany. Considering the number of patents on shallow drivers, and the fact that the inventor also previously developed transducers for Harman International and holds other key patents, this is no doubt an interesting document to analyze in depth. This article was originally published in Voice Coil, May 2017.

This review looks at a patent of parametric loudspeaker awarded in November 2016 to Luke Batchelder (Somers, NY), and J. Samuel Batchelder (Somers, NY) on behalf of Convey Technology, Inc. (Somers, NY). As James Croft (Croft Acoustical) comments in this patent review: "The parametric loudspeaker is one of those technologies that get rediscovered and “invented” about every 10 years." This article was originally published in Voice Coil, February 2017.

The patent reviewed here was granted to inventors Robert G. Johnston (Amprior Ontario, CA), and Sanford M.Gross (Owings Mills, MD), respectively the head of engineering of GoldenEar Technology, and one of its co-founders. The patent describes a subwoofer with two drivers on each side plus one passive radiator facing up and one passive radiator facing down. The passive radiator facing down effectively couples acoustic energy at very low frequencies into the floor.

Having reviewed previously one of the early Mayht Holding B.V. patents covering their general bipolar, interleaved multiple motor structure architecture, James Croft reviews the most recent US publication (2022). This one addresses the most dramatic claim for the Mayht transducer technology of the ability to provide a greater-than 10x reduction in enclosure volume, while maintaining the same efficiency and bandwidth as compared to the current state of the art. This article was originally published in Voice Coil, August 2022