The October 2023 issue of Voice Coil is packed full of loudspeaker knowledge. Vance Dickason kicks off the issue by writing about the recently announced new OEM Drivers from SB Acoustics and SB Audience. And that pretty much sets the tone for this magazine.In Acoustic Patents, James Croft reviews an interesting concept from Acoustic Metamaterials (from Scarsdale, NY), titled "Methods and Systems For Modifying Acoustics of a Loudspeaker Back Enclosure Using Active Noise Control." This patent, granted in November of 2021 to Gopal Prasad Mathur (CTO of Acoustic Metamaterials), details an active acoustics management system for loudspeakers, which is effectively an active low-frequency enclosure system, incorporating multiple woofers intercoupled in what is known as an isobaric or “compound woofer” enclosure, as James Croft explains. This has been an extensive area of research as he details, but this updated approach seems to deliver an effective contribution to exploring its benefits. Dr. Gopal P. Mathur has a career spanning four decades and is recognized for his technical work dealing with noise control, and research in acoustics, acoustic metamaterials, and active noise control.
Mike Klasco and Nora Wong (Menlo Scientific) provide an updated directory of Integrated Electronics for Loudspeakers. This includes vendors in the obvious categories of amplifier modules and plate amplifiers to use in speakers, but also all electronics and DSP solutions required for powered, portable, and smart speakers, as well as the most sophisticated soundbars and integrated systems. Check the updated listings of OEM, ODM, and Contract Manufacturers of Integrated Audio Products.
Meanwhile, Vance Dickason has been keeping busy working on Test Bench. In this issue he offers three different driver characterizations. Starting with the AMT100H driver from Eighteen Sound. The AMT100H is the "little brother" of the Eighteen Sound AMT200P (with the XMT200 horn) air motion transformer (characterized in the November 2021 issue). Features for the Eighteen Sound AMT100H, include a rectangular throat with a Polyimide (Kapton) diaphragm, a neodymium magnet structure, and a net weight of 1.84lb (0.835kg). This driver has a nominal 8Ω impedance, AES power handling of 25W (50W continuous) above 1.2kHz, sensitivity of 93dB, and a recommended crossover frequency of 1.2kHz at 24dB/octave. This AMT also has a damped rear cavity that includes a black emissive coating and heatsink fins for cooling enhancement.
Next, Vance Dickason tests an updated version of the popular TW030WA23/24 tweeter from Wavecor, the latest in the company's 30mm tweeter lineup. The A23 is the 4Ω version reviewed, while the A24 is the 8Ω version and they are both available without a faceplate for custom mounting (the TW030A25/26 model). Voice Coil's Test Bench featured all the original versions of this tweeter in 2009, 2012, and 2015. While the TW030WA23/24 have a very similar feature set to the Wavecor TW030WA13/14 tweeters, the biggest difference is a new graphene reinforced textile (Tetoron) 30mm soft dome. Like the TW030WA13/14, the feature set for the TW030WA23/24 includes a 30mm wide surround precision-coated cloth diaphragm optimized for high-frequency cutoff above 20kHz, internal chambers below the dome and surround, copper-clad aluminum voice coil winding with a vented voice coil former, flexible lead wires for large excursions with crossovers below 3kHz, and black anodized motor parts for enhanced cooling including a rear mounted aluminum heatsink.
Finally, Vance Dickason measures the Scan-Speak D2008/2010, the revised version of the classic dome tweeter from the Danish brand. The D2010 and the D2008 are two revised classic Scan-Speak 19mm soft dome tweeters, originally launched more than 35 years ago. Scan-Speak basically discontinued production of the original 19mm ferrite magnet soft dome models and replaced them with these new 19mm textile dome neodymium motor versions. Both are virtually identical except for the faceplates. The new D2008 has a solid plastic 92mm diameter faceplate), while the D2010 has a 98mm diameter plastic faceplate with an acoustic damping rubber insert. The feature set for the Scan-Speak D2008/D2010 tweeters include a low resonance dual rear chamber (Fs=550Hz) and a vented pole piece, rated for long-term maximum power handling of 150W (using a second-order 4kHz high-pass filter), and 89dB sensitivity.
The October 2023 issue of Voice Coil wraps up with Industry Watch, where Vance Dickason pays tribute to Kenton Forsythe (1944-2023), noted for his pioneering professional audio loudspeaker designs and known as the co-founder of Eastern Acoustic Works (EAW). Vance also reveals the fact that his Loudspeaker Design Cookbook Volume II is now available. Coincident with the recent publication of the 8th Edition of the Loudspeaker Design Cookbook Volume I, KCK Media has also released the Loudspeaker Design Cookbook Volume II, the retitled and re-released Loudspeaker Recipes book by Vance Dickason.
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