As Voice Coil enters its 37th publication year as an information resource for the loudspeaker industry, Vance Dickason reminds us how this "information super highway" for the loudspeaker industry came to be. The publication resulted from a conversation with Ed Dell (the founder and publisher of audioXpress) following the publication of the third edition of Loudspeaker Design Cookbook, which has just been released in its much-expanded 8th edition - for the first time available in full color and a hardcover collector's edition. Check it out here.In line with this issue's focus on bass, James Croft (Croft Acoustical) explores another loudspeaker-related patent, this time a Speaker Enclosure Venturi Expander invented by Ronald K. Taylor (Miami, FL). The use of the term "Venturi" relative to bass reflex system ports (or vents) has been adapted as a marketing term used to suggest a way to control flow and increase bass performance as popularized in the early 1970s by the B.I.C. Venturi loudspeakers, wherein a group of marketing folks and loudspeaker designers embarked on promoting the "Venturi Port." It is stated that according to B.I.C., the tapered duct used in Venturi speakers increased the sound pressure at the vent by as much as 140 times as well as providing improved loading of the rear of the speaker cone. The practical benefit was said to be high-efficiency bass performance from a compact enclosure, a combination normally difficult to achieve in an inexpensive speaker system. The subject of this month’s review is suggesting a different take on the "Venturi" concept, with a series of small shaped "steps" at the output of an expander that enhances the efficiency of the speaker enclosure.
The following contribution to bass response comes from Mike Klasco (Menlo Scientific), who once again explores speaker design techniques to achieve more bass, challenging Hofmann's Iron Law. Could be the same bass in a smaller enclosure, or deeper or louder bass for the same enclosure back volume, higher efficiency for a given alignment, or even cleaner lower distortion bass. Updating solutions discussed in previous articles, for this issue Mike Klasco talks about signal processing, box stuffing, and finally changes in the driver design itself. "When these different approaches are combined, the impact is multiplied, and achieving a game-changing product comes within reach," he says. Included in the report are Waves MaxxBass, the Bongiovi Virtual Subwoofer (VSub), SubVo, Servobass, Dinaburg Technology, WaveLock, the Klippel Controlled Sound (KCS) technology integrated in a Nuvoton audio amplifier, and other companies, products, and technologies.
And in Test Bench, Vance Dickason characterizes the 6" WF152BD09-04 midbass driver from Wavecor, part of a new line of midbass models using a unique proprietary interwoven Kevlar and carbon fiber cone material. The 7” version, the WF182BD13, was featured in Voice Coil August 2023. Wavecor's 4Ω WF152BD09 has a generous feature set that includes a cast-aluminum frame with six narrow tapered spokes, substantially open below the spider mounting shelf for voice coil cooling. Other features include a vented inverted dome-type phase plug (no dust cap) and a shallow profile low loss high Qm NBR surround, accompanied by a flat 4" diameter black cloth spider. All this is driven by a 1.25" diameter two-layer voice coil wound with round copper wire on a black fiber glass non-conducting former and the Wavecor Balanced Driver T-pole ferrite magnet motor system.
In a second Test Bench report, Vance Dickason measures the UF295FAS Thin-Profile Dipole 10" Woofer from Neotera. This new 10" thin-profile woofer comes from Neotera, a new company headquartered in Sweden, founded by a diverse group of loudspeaker/electronic design veterans, who have launched their first products in 2023 and plan to launch several others for professional and consumer audio applications in 2024. Maurizio Servadio is the engineer who invented the Neotera Ultraflat technology and is based in Italy where the UF295FAS is manufactured. This thin-profile woofer with a depth of 2.6" and with a low-frequency response down to 29Hz, also has an upper frequency response that allows it to be crossed over as high as 1kHz. However, what really distinguishes the UF295FAS is that it is specifically designed for dipole system applications. The cone is a fiberglass/Rohacell sandwich single piece (no dustcap), suspended by two narrow rubber surrounds. The cone is driven at its perimeter by a large 11" voice coil, somewhat similar to the Prescient Audio TD-12 subwoofer reviewed in the August 2015 issue of Voice Coil. The motor structure is also unique in that it uses a series of 72 28mm-high neodymium bar magnets to directly drive the 7mm-high voice coil for a 10.5mm Xmax.
This issue of Voice Coil is complemented with the traditional dose of Industry Watch updates, selected by Vance Dickason. Content includes details of recent acquisitions, such as Eminence by B&C Speakers, and JL Audio by Garmin. Also highlighted is the recent release by KCK Media, of Vance Dickason's Loudspeaker Design Cookbook Volume II, which is the re-released and re-titled Loudspeaker Recipes. The Recipes book has long been out of print and includes valuable speaker design tutorials, including a deep exploration of two-way passive network design that expands the crossover technology chapter from the Loudspeaker Design Cookbook. On request from Vance Dickason, the Loudspeaker Recipes was launched as Loudspeaker Design Cookbook Volume II, priced at $39.95 and now available here.
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