Get Your Copy of Voice Coil September 2019 Before Heading to CEDIA!

In Industry News & Developments, Vance Dickason highlights the reasons why this year’s Custom Electronic Design & Installation Association (CEDIA) Expo is an important event for the loudspeaker industry. Once again being held in Denver, CO, at the Colorado Convention Center from September 10–14, with the actual exhibit part of the show taking place from September 12–14, apart from the outstanding exhibits, there will be a wide selection of workshops, classes, and seminars of interest to any loudspeaker professional.

In Spotlight for this month's edition, Mike Klasco (Menlo Scientific) anticipates the main highlights for the 2019 AES International Conference on Headphone Technology, happening in San Francisco, CA, as this edition is published. The Audio Engineering Society’s second International Conference on Headphone Technology is an invaluable learning opportunity for anyone who works in the headphone industry and Voice Coil provides an essential insider's preview.

In Acoustic Patents, James Croft (Croft Acoustical), reviews a new Multi-Driver Loudspeaker with Cross Coupled Dual Wave-Columns, recently awarded to the author (yes, he provides full-disclosure) together with Michael Smithers (AU) and Garth Showalter (US), listed as inventors and assigned to Dolby Laboratories. The abstract describes a dual wave-column, dual-driver loudspeaker enclosure, where the two drivers are cross-coupled through their respective front and back sides by two single exit wave columns. At the 1/4 wavelength frequency of the waveguide length, both drivers resonate with the waveguides, and cone motion is minimized while output is maximized. At the 1/2 wavelength frequency, the front wave of the first driver is in-phase with, the rear wave of the second driver such that the output is increased, reinforced, and smoothed at that frequency. At the 1/3 wavelength frequency, the two wave-column mouth outputs exhibit acoustic mutual coupling, which boosts acoustic output and reduces cone motion at the critical maximum displacement frequency.

The review discusses previous tapped wave-column designs and patents awarded to Tom Danley, of Danley Sound Labs, an earlier 1952 concept from Jensen Manufacturing, and a first patent granted for the technology in US to William E. Glenn in 1956, as well as related patented designs from Bose and Matsushita (Japan), and even existing DIY designs, to explain how the inventors have achieved an improved differentiated design.

For this month's Test Bench, Dickason characterizes the PD.124NR1, a new high power 12” neodymium midbass driver from Precision Devices and from Eastech’s Punktkilde line, the FSA044010-0802, a 1” titanium dome tweeter.

The Precision Devices 12” PD.124NR1 finds applications as a midbass driver in multiway systems or as a dedicated woofer bass reflex or horn-loaded designs. Its feature set is like most high performance pro sound drivers, fairly substantial, starting with the proprietary six-spoke cast-aluminum frame incorporating six 30 mm × 2 mm rectangular vent holes in the area below the spider mounting shelf for enhanced voice coil cooling. The cone assembly consists of a curvilinear paper cone along with a 5” diameter paper dust cap. Compliance is supplied by pleated coated cloth M-type surround and from two silicone 6” diameter flat spiders (dampers) mounted back to back on an aluminum standoff at the base of the frame. The PD.124NR1’s motor design is unique, and utilizes a radial charged neodymium magnet structure, a 101.6mm (4”) diameter voice coil wound with round copper clad aluminum wire (CCAW) on a non-conducting glass fiber former. Motor parts, such as the return cup and rear heatsink plate are coated with a black heat emissive coating for improved cooling, with the cooling additionally enhanced by a 35 mm flared pole vent (flare extends to 60 mm), plus six 10 mm diameter vents over the vertical placed neodymium magnets.

The second transducer is from Eastech's new Punktkilde line of home hi-fi drivers built in China and designed in Denmark by Scan-Speak engineers. The FSA044010-0802 is a recently released Punktkilde tweeter, featuring a 1” damped titanium dome diaphragm, dual magnet neodymium motor, a cast-aluminum anodized red faceplate (other colors are available), and an 8 Ω voice coil. This is a very cosmetically attractive tweeter with a polished return cup with a metalized stick on the back.

And of course, Voice Coil September 2019 also includes the usual compilation of important updates in its Industry Watch section, compiled by Dickason.

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