The Voice Coil November 2024 issue features a fascinating Spotlight article detailing new Fiber-Reinforced Composite Technology for Vibration Reduction in High-Performance Applications. As the Chief Technology Officer and Principal of Countervail Products, Anthony Caiazzo details the Countervail family of vibration canceling materials, which features a patented approach that has been shown to provide exceptional levels of vibration damping in many common structural configurations.Countervail materials not only cancel vibrations, but they also contribute to the stiffness of the structure and typically don't significantly change the component manufacturing process. This innovative approach meets the demand for advanced fiber-reinforced composite materials to deliver the performance that both manufacturers and consumers demand, allowing for lighter products without unwanted vibrations that affect product performance or reduce service life.
As scheduled for this issue, Mike Klasco revisits the topic of new loudspeaker innovation for increased bass response. In an article titled simply "More Bass!", Klasco explores developments that allow speaker designers to "bend the rules" and challenge Hofmann's Iron Law, which states that one needs to pick between low-bass reproduction, small (enclosure) size, and high (output) sensitivity - where any two of the parameters always compromise the third. For this issue of Voice Coil, readers will learn that approaches combining psychoacoustic signal processing, feedforward/feedback amplifier-speaker error compensation, motional feedback, along with the weird science of virtual back volume, expanding meta-materials, and negative springs might allow a recipe for the much-sought-after improved bass response.
And appropriately for an issue that focuses on reinforced loudspeaker performance, James Croft (Croft Acoustical) also writes about negative-spring woofer concepts, and its compelling theoretical potential to overturn Hofmann’s Iron Law and provide significantly deeper bass from much smaller enclosures (at least 1 to 2 octaves lower than the “Iron Law” limits). For his Acoustic Patents article, Croft reviews a patent titled "Electroacoustic Drivers and Loudspeakers Containing Same" awarded to notable inventors Joseph Pinkerton, David Badger, James Andrews, William Lackowski, and William Everett, on behalf of Clean Energy Labs and Brane Audio. A second patent is also covered in the review, titled "Loudspeaker and Methods of Use Thereof," also awarded to Joseph Pinkerton and David Badger, on behalf of Clean Energy Labs. The first patent was granted in June 2024, and the second earlier in March 2023.
Of course, many Voice Coil readers have heard of Brane Audio and the company's claims for its Brane-X loudspeakers, which assert to utilize a "Repel/Attract Driver" (R.A.D.), incorporating a Magnetic Negative Spring. As James Croft notes, "over the last three decades of writing patent reviews for Voice Coil, I have reviewed and identified more than two dozen patents on Negative-Spring Woofer concepts." Apparently, the R.A.D. driver where these inventions are implemented, using a unique high-excursion position sensor, can rightfully claim a unique breakthrough in this concept, and Voice Coil readers can read all about it in this November 2024 issue.
Not surprisingly, given the extensive coverage of the topics mentioned, Vance Dickason could only fit one driver in his Test Bench section. And this month, the driver elected is the MT19CP-8, a new 7.5" coaxial driver from SB Acoustics' prestigious Satori line. This well-designed coaxial driver is built on a rather stylish aluminum-cast frame, totally open below the spider, with what appears to be a second part of the frame being an injection-molded rubber trim piece that is attached to the motor assembly. The woofer cone is SB's proprietary Egyptian Papyrus material with a three-roll coated cloth-type surround, driven with a 1.52" diameter voice coil and neodymium magnet. The high-frequency device is mounted on a pole inside the long woofer voice coil with a plastic housing that includes a 6mm long horn-loading ring. The 1" tweeter is comprised of a coated cloth-type dome diaphragm, powered by a neodymium motor, which incorporates a resonant back chamber design. Like the woofer motor, the voice coil for the tweeter is also wound with copper-clad aluminum wire (CCAW) on a fiberglass former and includes a copper cap-type shorting.
In a reference preamble to this month's Test Bench, Vance Dickason writes about the purpose of his long-lasting column, for those readers who are less familiar with the concept. The original "mission statement" for Voice Coil's Test Bench was to present a comprehensive objective measurement data set that would enable a speaker systems engineer (like Dickason) to decide whether or not to get a sample of the driver, which is why he always refers to them as explications. Test Bench articles were never intended as a review... Important to have in mind.
And in this month's Industry Watch section that closes the November issue, Vance Dickason signals the 38th anniversary of Voice Coil and highlights new transducers and audio industry initiatives of interest for loudspeaker engineers.
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