From Speakers to Headphones in Voice Coil June 2019

May 24 2019, 09:25

The June 2019 edition of Voice Coil is now available, and this month's edition focuses on Headphone Measurement Equipment. Mike Klasco (Menlo Scientific) explores headphone measurement gear and discusses the latest artificial ears, head/torso R&D manikins, production line testers, and smartphone manikin head mount positioners. "Headphones are now one of the hottest audio categories and speaker engineers need to be able to test those headphones. For a speaker engineer to switch from testing a bookshelf speaker to testing a soundbar is trivial, but to test a headphone, let alone a wireless or an active noise canceling (ANC) design, is not the same. The test instrumentation category, which we have loosely categorized for 'headphones' includes passive, active and wired earphones, headsets (including microphones), and also solutions for mobile phones and the like."

Following Mike Klasco's introduction to the topic, this edition of Voice Coil includes a complete directory of Headphone Test & Measurement Gear 2019, and provides profiles of some of the better known vendors in the industry. The vendors compilation was also written by Mike Klasco and includes company profiles that allow a wide perspective on the tools that professionals need the design and evaluate headphones and earphones.

Next up, is a report on the recent Asian Trade Show Spring Marathon, where Mike Klasco and Nora Wong (Menlo Scientific) share their experiences while visiting some of the largest Asian consumer electronics shows that always happen at this time of the year, and normally repeat again in October. An important report to understand how to best leverage these shows and identify new products and partnerships. "Manufacturing mainstream audio products in the US is in the distant past and perhaps in the future, but product development combined with offshore factory partner selection is today’s reality. For getting a sense of the market and finding new vendors, we have trade shows," Klasco writes.

In this month's Acoustic Patents article, James Croft (Croft Acoustical) reviews a new Loudspeaker Enclosure with a Sealed Acoustic Suspension Chamber design, invented by Rohan Jaguste (Johanneshov, Stockholm, Sweden) and patented in 2018 on behalf of Swedish company Keyofd Aktiebolag, also based in Stockholm). This is a new approach to an area that has been extensively researched - and patented - in an effort to improve low-frequency performance in speakers. The specific design under review describes a loudspeaker enclosure housing a sealed acoustic suspension chamber, where a driver and a passive acoustic diaphragm on opposite sides are combined with a first bandpass chamber connected to the sealed acoustic suspension chamber by the passive unit in a curved structure. Using his extensive knowledge of the design, James Croft discusses prior art approaches, inherent problems and areas where some designs have been more effective than others, and looks at the potential for the new patented design to eventually provide significant large signal output advantages over current systems. A very detailed and informative review that will be valuable reading for any speaker designer.

For the June 2019 Test Bench, Vance Dickason characterizes two new woofers from Faital Pro and Wavecor. The drivers are the new 6” 6PR160 pro sound midwoofer/midrange from Faital Pro, and the new shallow mount 10" home audio subwoofer, the SW280WA-01, from Wavecor.

The Faital Pro 6PR160 is a pro-audio oriented woofer design that features a proprietary four-spoke cast-aluminum frame, and does not have venting below the spider mounting area. Cooling for this driver is provided by a 12 mm diameter pole vent with a 22 mm flared exit. The cone assembly consists of a curvilinear paper cone with a front side waterproof hydrophobic coating and a 2.2” diameter convex paper dust cap, both waterproofed. Compliance is provided by a triple-roll treated poloycotton pleated surround with the remaining compliance coming from a 4” diameter flat cloth spider with constant height waves. The motor design on the Faital Pro 6PR160 utilizes an FEA-designed neodymium ring magnet, with a 37 mm (1.46”) diameter voice coil wound with round aluminum wire on a nonconducting glass fiber former. The neodymium ring magnet is sandwiched between a milled and polished front plate and a cast-shaped T-yoke with a 13.5 mm bump-out.

The new SW280WA01 11” low-profile subwoofer from Wavecor, represents some interesting driver technology with applications in small narrow spaces. The SW280WA01 has a unique and interesting feature set that starts with an extremely shallow 76 mm (3”) depth proprietary eight-spoke vented cast-aluminum frame. If inset mounted into a 0.75” MDF baffle, the driver would only protrude into the enclosure by about 2.45 inches! Other features include the incorporation of a flat 10" glass fiber/PMI foam sandwich cone with dual surround and no-spider suspension, along with an innovative design that facilitates mounting the motor structure inside the frame. The cone is driven by a 39 mm diameter voice coil using a vented fiber glass former wound with round copper wire. Wavecor also incorporated its “balanced drive” motor configuration that features an extended and shaped pole piece. Motor parts have a black emissive coating for enhanced cooling, along with a dual flared 10 mm diameter pole vent. Last, the voice coil is terminated to gold terminals located on opposite sides of the frame to discourage rocking modes.

The June 2019 edition of Voice Coil is complemented with the customary Industry Watch, including an obituary for George Robert Koonce (December 11, 1935 – April 25, 2019), an esteemed speaker designer and author of many books and articles for Voice Coil and audioXpress, covering valuable perspectives in acoustics, electro-acoustics and computer-aided design projects. Dickason also writes about the just-announced “super” company, Purifi Audio, new products from Scan-Speak, and many other product, corporate and industry news.

All this is now available for download and already in the mail for print subscribers. Subscribers can go to - - to download this issue.

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