In this issue of Voice Coil, Mike Klasco (Menlo Scientific) recaps the exciting progress happening in magnets, a critical technology field for the loudspeaker industry, while reporting simultaneously on other ongoing developments in signal processing that will impact speaker design. This a great way to kickstart another issue of Voice Coil.As scheduled, Nora Wong (Menlo Scientific) compiled a new updated directory of Microspeaker Vendors for 2023, focusing on smartphone and laptop applications, with an additional subdirectory on MEMS microspeaker transducers. This last product segment is evolving rapidly and it's important to identify and characterize the leading players. MEMS speakers, combined with signal processing and in some cases even the amplifier, are finally entering the market in true wireless stereo (TWS) earphones and hearing aid applications. Many companies are exploring the technology's potential as tweeters and as an alternative to balanced armature (BA) transducers.
For this issue's Acoustic Patents column, James Croft offers an interesting perspective of an application that is proving critical for the latest-generation automotive audio systems, and not surprisingly is receiving strong attention from major players, resulting in many new patents. This review looks at three very complementary patents of loudspeakers that are acoustically coupled to the interior of a vehicle and externally ducted to the exterior. The two first patents are from Bose Corp., including one that results from its cooperation efforts with Porsche and therefore is assigned to both companies. The third one was assigned to Harman International.
In all three patents, the goal is to achieve a way to manage the pressure differential that exists between the interior and the exterior of the vehicle, therefore enabling a way to leverage the large "enclosure" volume represented by the vehicle cabin for low frequency extensions. Prior art reveals that this is an area that has been previously explored, but has now received further impetus due to the requirements of electric vehicles and the viability of using modern technology.
In Test Bench, Vance Dickason characterizes the new 1" PEEK Diaphragm compression driver from SB Audience, the pro audio brand of Sinar Baja Electric and SB Acoustics. The company recently released six new compression drivers — four with Polyether Ether Ketone (PEEK) diaphragms and two with titanium. For this Test Bench, the SB Audience Russo 44CDN-PK is combined with the H250 90°×60° exponential horn. The driver features a 44.3mm (1.75") diameter voice coil driving a single piece PEEK diaphragm and surround, and including a FEA-optimized neodymium ring magnet motor structure, annular phase plug design, and a cast-aluminum damped rear chamber. This driver has a 60W AES power handling rating (120W maximum), with a 1.8kHz recommended crossover frequency. The 90°×90° H250 horn that accompanied the 44CDN-PK is a constant directivity category device made from injection-molded ABS with a 600Hz cut-off frequency.
The second driver for this month's Test Bench is the B&C Speakers DCX354 ring radiator coaxial dual-diaphragm compression driver and respective horn. This is a similar design to its big brother, the B&C Speakers DCX464 that was featured in the October 2019 issue of Voice Coil. The DCX354 now makes a total of four coax compression drivers in the B&C Speakers line-up. While B&C Speakers made a significant number of improvements in the new DCX354-16, it is still basically a smaller version of the DCX464. The DCX354 has a 3" midrange diaphragm and a 2" and is good down to 400Hz. The horn tested with the DCX354-16 was the new B&C Speakers ME464, a very large horn device made of durable polyurethane plastic with an 80°×60° nominal coverage pattern.
The DCX354-16 ring radiator is a 1.4" (36mm) throat compression driver, and that is for both the midrange driver and the high-frequency driver, which means that B&C Speakers has found a way to mix both drivers in the same throat. The midrange compression driver has a 16Ω nominal impedance, continuous power handling of 180W, 112.7dB (1W/1m) sensitivity, and a frequency range of 400Hz to 6kHz. The high-frequency section is also 16Ω, and has a 160W continuous power handling rating, with a recommended high-pass crossover frequency from 4.5kHz to 5kHz.
And in this month's Industry Watch, before discussing the latest announcements from Eighteen Sound, Lavoce Italiana, Loudsoft, SEAS, and Listen, Vance Dickason discusses the 46th anniversary release of the his Loudspeaker Design Cookbook 8th Edition! Get all the exclusive information of the much-anticipated new and much-improved edition of the book!
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