The first issue of 2025 is now available, and it is another solid example of why, after 38 years, Voice Coil remains the reference periodical for the loudspeaker industry.This issue opens with another great article by Claus Futtrup, this time with direct support from Jeff Candy, the two creators of Speakerbench, the free to use web-based application for low-frequency analysis and design of loudspeakers. For the January 2025 issue Claus Futtrup brings us another follow-up article for the “Computation of Bass Reflex Alignments” article series that was published in Voice Coil’s May through October 2024 issues. This time, the article discusses the important Quasi-Alignment Families where the fundamental idea is trying to approach a roll-off similar to the Butterworth B4 alignment (a maximally flat response) but compatible with real systems for which the driver Qt will not allow a true B4 alignment. Something that Neville Thiele defined earlier as a QB3, or Quasi Butterworth alignment.
The next article in this issue comes from Dave Morrison, the founder and president of IsoAcoustics, talking about "Spikes & Isolation: The Art of Speaker Decoupling for Optimal Audio Performance." Dave Morrison founded Ontario-based IsoAcoustics in 2010 after several years of research, resulting in a series of patented isolating stands that quickly conquered the studio monitor world and evolved into a whole range of isolation products now embraced in high-end audio, installation, and backstage guitar amplifiers. For Voice Coil, Dave Morrison wrote an interesting piece that sums up his vast experience in the field, working with professional audio engineers, loudspeaker designers, and music lovers all over the world. His article explores how speakers physically interact with their supporting surfaces, the key factors that affect speaker decoupling, and the pros and cons of many common approaches.
As scheduled for the January issue every year, Nora Wong and John Lam (Menlo Scientific) compiled another valuable edition of the Earphone and Headphone Manufacturers Guide, containing an updated list of many of the leading OEM/ODM headphone and earphone factories and a subdirectory of headphone parts vendors. This parts subdirectory lists suppliers of acoustic resistance woven and non-woven fabrics, wire meshes and diaphragm membranes, ear cushions and ear tips, plus complete headphone drivers.
For this month's Test Bench, Vance Dickason has spent some time characterizing the new Scan-Speak D3004/666000 tweeter, the first to combine a metamodal Thin-ply Carbon Diaphragm (TPCD) dome with the company's AirCirc motor. This new Scan-Speak tweeter is not a common "evolutionary" design but a joint manufacturing project with Swedish company Composite Sound to develop new second-generation TPCD diaphragms with the characteristics and able to rival the performance levels of a beryllium dome.
Metamodal TPCD diaphragms can be manufactured according to a targeted response, precisely controlling the cone modes and resonances by judiciously adjusting the location of weight and thickness in the diaphragm. This latest product expands on the previously released D3004/606200 1" TPCD, both of which are replacing Scan-Speak’s previous beryllium versions in the Illuminator series. For the D3004/666000 tweeter, Scan-Speak combined the thin-ply carbon metamodal designed diaphragm with an AirCirc motor design with six neodymium slug magnets and its proprietary SD-2 motor structure, a large roll coated cloth surround, and a black anodized machined aluminum faceplate that can be custom laser engraved.
The next driver in Test Bench might seem more conventional in comparison, but it's effectively an excellent example of performance optimization for low frequencies. The Dayton Audio UMII10-22 Ultimax II 10" Subwoofer is a recent example of the upgraded, high-performance subwoofers that succeeded Dayton Audio's original Ultimax subwoofer line. Available for now in four diameters (18", 12", 10", and 8"), the common feature set for the new line includes a large aluminum shorting ring and aluminum pole sleeve for lower magnetic distortion, a lightweight and rigid woven carbon fiber cone assembly, high Xmax (18mm on the 8" up to 28mm on the 18"), with a frame and motor designed with extensive thermal venting, all optimized for compact sealed enclosures.
The focus of this month's Test Bench is on the Ultimax II10-22 10" version, featuring a proprietary eight-spoke cast-aluminum frame that is substantial enough to support the heavy motor assembly and incorporates eight trapezoid vents located below the spider mounting shelf. Other features include a very stiff and thick curvilinear profile carbon fiber cone, further stiffened by a heavy paper cone section that attaches to the bottom of the carbon fiber cone to the voice coil neck joint. Suspension is provided by a FEA-optimized low-loss, high profile NBR surround plus two flat 6" diameter cloth spiders. All this is driven by a 2.5" diameter four-layer voice coil wound with flat copper wire on a vented aluminum former. The motor system powering the cone assembly utilizes two 20mm thick ferrite magnets sandwiched between a milled and polished 10mm thick front plate and a milled and polished shaped T-yoke.
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