Preserving Precious Sounds with audioXpress November 2018

October 9 2018, 13:00
In this edition, audioXpress pays tribute to one of its most esteemed and prolific writers, Ron Tipton (1936–2018). In our cover feature, Scott Dorsey details his fascinating visit to the Library of Congress National Audio-Visual Conservation Center. Tom Perazella concludes the construction of his flagship Egg Speakers, Andy Lewis explains more about Back EMF, Peter Lehmann shares his time-alignment design for a two-way speaker, and Ethan Winer shares his experience with the affordable LabNation SmartScope USB oscilloscope. And that's just the start of another great edition, now available in print and online.
There are times when we just need to stop and look back to appreciate and be thankful for those who share their work and lives with us and unfortunately have departed. Just in the past few weeks we have mourned the loss of Siegried Linkwitz (1935–2018) and David Clark (1941–2018). Great engineers, brilliant minds, friends which will be missed. In Voice CoilOctober 2018, Vance Dickason writes and honors the memory of Siegried Linkwitz.
Unfortunately, we also received news of the passing of a very close friend and contributor for audioXpress, Ron Tipton. Born in Chicago, IL, Ron studied electrical engineering in New Mexico State University and was retired from an engineering position at White Sands Missile Range. In 1957 he started Testronic Development Laboratory (TDL Technology, Inc.) to develop audio electronics. During the 1960s and 1970s, TDL built active filters and audio test equipment for well-known companies such as Bose Corp. and Acoustic Research. He remained the TDL president and principal designer until 2015. In this edition, audioXpresspays tribute to one of its most esteemed and prolific writers. Ron Tipton (1936–2018)
In our cover feature, Scott Dorsey details his fascinating visit to the Library of Congress, which was an essential part of the recent Audio Engineering Society (AES) International Conference on Audio Archiving, Preservation, and Restoration. This sold-out event, held at the Library of Congress National Audio-Visual Conservation Center (NAVCC) Packard Campus in Culpeper, VA, June 28-30, 2018, enabled Scott to get close with the world's foremost experts at playing records, and the people who spend all day at work collecting records, repairing and preserving records, and playing back records. 
As in the past two editions of audioXpress, the November issue continues to focus on speaker design and construction. In this edition, Tom Perazella concludes the construction of his flagship Egg Speakers, using the latest generation of SB Acoustics' Satori high-end drivers, with a powerful low-frequency extension base featuring Dayton Audio woofers. In this third part of the series, Perazella wraps up the construction and assembly of his three-way double cabinet design, detailing the automotive-grade paint finish and the crossover design.
Also focusing on speaker design, Andy Lewis returns with another installment of his fascinating exploration of Back EMF Phase Relationships in Moving-Coil Loudspeakers. This article explores the Electrical and Newtonian filters and their intersections, observations on reactive parallel filters as pertains to Back EMF and energy losses, and expands upon concepts hinted at in his previous articles on Back EMF.
And for those looking to explore a different concept, Peter Lehmann discusses a Reflective-Way Two-Way Speaker, which is better described as a speaker system with an integrated reflector for the tweeter, allowing better control over the time of arrival of high frequencies. This is the first part of a well-documented project where the author explores the concept, before providing construction details and his own test data.
And because a well-equipped lab bench is an essential component for any audio-related activity, Ethan Winer shares his experience with an affordable new USB test and measurement platform, the LabNation SmartScope. In his review, Winer explains why this digital oscilloscope, signal generator — analog and digital — and eight-channel logic analyzer from LabNation turned out to be perfect solution for his needs. "Besides doing everything I need and then some, it’s only slightly larger than a pack of cards. So I bought my own and have used it with great success for several months."
Another fascinating read is Richard Honeycutt's third article on Modulation Distortion in Loudspeakers and Its Detectability, now focusing on experimentation to find the threshold of detectability of Doppler distortion. After having discussed the detectability of Doppler distortion in previous theoretical and experimental studies, in this article Richard presents the results of a small human study, and compares its results with those of previous researchers. This study was reported at the May 28, 1971, meeting of the North Carolina Regional Chapter of the Acoustical Society of America.
In his column, Hollow-State Electronics, Richard Honeycutt also discusses screen-grid biasing, and compares several methods of setting screen-grid voltage in power amplifiers to see their distortion performance.
This edition also features a trip to the past, with a review by Morgan Jones of a true audio classic, High Fidelity Circuit Design, by Norman H. Crowhurst and George F. Cooper. This book, originally published more than 60 years ago, has been republished by Linear Audio.
And in the second half of a two-part book review, Gary Galo details the remaining chapters and shares his final thoughts on Douglas Self’s recently published book Electronics for Vinyl.
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