In this edition of Voice Coil, Mike Klasco writes about Dr. Kurt Müller’s 100-Year Anniversary, Mike Klasco and Nora Wong compiled an updated Integrated Electronics for Loudspeakers directory, and James Croft reviews an intriguing patent of a Vertically and Horizontally Balanced Subwoofer. For this issue’s Test Bench, Vance Dickason focused his full attention on another innovative driver from Purifi Audio, this time the PTT5.25X04-NFA-01 5.25” Midbass Woofer.
On Industry News & Developments, this edition of Voice Coil opens with the highlights of the recent software update for the Klippel Analyzer System, with various new features for both R&D and QC applications. This second 2022 update is now available and is free of charge for any users of dB-Lab major version 212 or QC 7 and includes a new Documentation module (DOC) for any dB-Lab operation (R&D or QC), a Transducer Electronic Data Sheet (TEDS) for any KA3 having QC-Card(s) installed, and a few more new useful features.
In this issue, Mike Klasco also writes about Dr. Kurt Müller’s 100-Year Anniversary and revisits the milestones of this important supplier of cones, suspensions, dust caps and surrounds company. Perhaps the oldest surviving cone factory in the world and certainly one of the most advanced, DKM was originally founded in 1922, in Berlin, and in 1970, extended its product range with the acquisition of Pulsonic Ultrasonics Limited (now known as Kurt Mueller UK Ltd) in the United Kingdom. Happy Birthday!
And since this is the October issue, Mike Klasco and Nora Wong have compiled the traditional Integrated Electronics for Loudspeakers Directory, with updated listings of key technology, parts and production suppliers for manufacturers of soundbars, smart speakers, and all powered speakers. Naturally, the directory includes amplifier modules and all the relevant sources of associated electronics and digital signal processing (DSP).
On Acoustic Patents, James Croft reviews an intriguing patent of a Vertically and Horizontally Balanced Subwoofer, filed in 2015 and granted in 2016 to inventor Robert G. Johnston (Amprior Ontario, CA), on his own behalf. This is one of those patents that James Croft is in a unique position to contextualize, given his extensive experience in the loudspeaker patents field. This patent describes a subwoofer with one transducer facing to the right and another transducer facing to the left, which effectively cancels out transducer cone mass induced vibration within the enclosure. The enclosure also has one passive radiator facing up and one passive radiator facing down, effectively coupling acoustic energy at very low frequencies into the floor. By avoiding vibration and cabinet motion, the invention addresses some of the most problematic aspects of low frequency designs. There is just one question, which is the number of prior art inventions already recognized in this field. Read what James Croft has to say.
For this issue’s Test Bench, Vance Dickason focused his full attention on another innovative driver from Purifi Audio, this time the PTT5.25X04-NFA-01 5.25” Midbass Woofer. This is the third Purifi woofer to be examined in Test Bench (see Voice Coil July 2021, for the 6.5” PTT6.5X04-NFA-01 and the November 2021 issue, for the 4” PTT4.0X04-NFA-01 woofers). As Vance Dickason stated in the previous explications, there is no question that this OEM driver manufacturer’s background is impressive and that Purifi’s transducer technology is some of the most advanced and out-of-the-box thinking in the current paradigm.
The Purifi Audio driver for this month’s Test Bench is the newest member of the Purifi midbass woofer family of drivers and the core technology is pretty much identical to the PTT6.5X and PTT4.0X, and includes the same constant Sd surround and low magnetic hysteresis motor design. The cone assembly consists of a slightly curvilinear profile paper cone made with a proprietary fiber mix, a 2.8” concave dust cap that covers about 90% of the cone surface, plus the addition of a rather large V-shaped edge reinforcing ring glued around the outside rim of the back side of the cone, with compliance provided by a unique NBR surround, which is again an entire story in itself, with a combination of alternating sections of both reverse roll and positive roll, plus some interesting undulations within the alternating sections. As it should be, Vance Dickason explored all the design aspects and measured all the relevant and unique features of this very original design.
This issue of Voice Coil closes as usual with a generous dose of Industry Watch news, carefully selected among the relevant announcements and appointments. As always, mandatory reading for speaker professionals.
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