audioXpress September 2021 is now available online and in print and celebrates its Speaker Builder magazine origins, once again offering an expanded focus on loudspeaker building, design, and testing.
Highlighted on this edition's cover is a dedicated Market Update feature on Speaker Technology written by Mike Klasco. Discussing new ways to formulate speakers, this article looks at recent companies, products, and inventions that are pushing speaker design to new levels. From innovative speaker designs and new transducer topologies to feed-forward protection circuits, this is an overview of innovation happening right in front of us. Detailed in the report are technologies from Klippel and Nuvoton, Dinaburg Technology, Resonado Labs, Trulli Audio, Fibona Acoustics, Earthquake Sound, and Mayht Technologies.
One of the major highlights for this edition is certainly an excellent article by Claus Futtrup and Jeff Candy on Parameter Estimation and Box Simulation with Speakerbench. In the first part of this work published in our August 2021 edition, the authors discussed the difficulties in estimating cabinet losses using the classical Thiele-Small framework, and proposing a solution using an advanced transducer model. In this second and final article, the authors detail how Speakerbench offers an accurate and practical approach to this problem.
Speakerbench is a web-app and works on any computer, tablet, or smartphone with a browser, without any software installation required. It was created by Futtrup and Candy in an effort to provide more advanced modeling and high-quality transducer data even for the DIY speaker builder. In this article, the two speaker experts will demonstrate how users will be able to easily and accurately determine the best suitable box volume for a loudspeaker system.
And audioXpress is also proud to feature an article detailing how Geoff Hill, loudspeaker engineer, author, and inventor, developed the Tetrahedral Test Chamber to solve the longstanding problem of making consistent loudspeaker measurements. In "The Tetrahedral Test Chamber Story," Hill explains how the concept was born out of necessity, simple wavelength theory and Beranek's wedges, tetrahedral structure, measurement theory, and building upon experience gained in designing chambers in Europe, US, and Asia. This innovative loudspeaker test chamber is now defined in international standards and in use throughout the world and scalable to any size of loudspeaker driver.
In this speaker-focused edition, we pay tribute to the life and achievements of Roger Russell (1935-2021). Roger Russell was an unsung hero of loudspeaker design and development. Director of Acoustic Research at McIntosh Laboratory for 25 years, he wrote several articles for audioXpress about loudspeaker design and hearing. After his passing, those who knew him submitted comments about Roger, his impact on their lives, and his contributions to the loudspeaker industry. As part of the tribute, we are also publishing the last article that he submitted to audioXpress prior to his death, “The Sound of a Column” - a personal review of his career as a loudspeaker designer and his proudest achievements.
This edition also includes a nice DIY project from Ken Bird. In this simple speaker project, our veteran speaker builder and longtime contributor to audioXpress proposes a versatile and affordable dual column speaker design, great for home listening and matching with home entertainment systems. This system uses the principle of mass loading through a narrow duct to the port output, while its narrow configuration and tunnel partition provide a solid cabinet with low resonance. Driver choices include two Hi-Vi woofers and a Dayton Audio 1” dome tweeter, but the project can be easily modified with different options.
The next project include in this September 2021 edition, is also speaker-related. Peter H. Lehmann, an author who has focused his efforts on enhanced reproduction to “fix stereo,” designed an “upmix” solution to derive a “real” center channel from the left and right channels of any conventional stereo recording. The signal-processing unit's outputs can be fed to a center loudspeaker to supplement the quality and localization of the phantom center image.
Also featured in this edition is an extended review of the Parasound Halo JC 5 Stereo Power Amplifier by Oliver A. Masciarotte and Stuart Yaniger. Parasound offered to send the Parasound JC 5, its largest stereo power amplifier for audioXpress evaluation, and anticipating the fun of this John Curl design, Masciarotte accepted the challenge. The JC 5 delivers an aggressively biased 12W into 8Ω in Class A mode, plus 400W Class AB into 8Ω and 600W per channel into 4Ω. In stereo mode, it is stable into temporary loads as low as 1.5Ω, and can deliver 1200W into 8Ω when bridged. In this review, Yaniger confirmed the merits of this powerhouse with actual measurements.
And finally, Richard Honeycutt offers an enjoyable journey back in time to the revisit the early sound and music reproduction systems for home listening in his Hollow-State Electronics column.
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