As planed, audioXpress April 2023 covers the exciting world of technology that is converging around the ear. From self-fitting hearing aids to augmented audio, from hearables to Headphone 3.0, all the latest product designs, technology platforms, and cutting-edge possibilities of edge AI, active noise cancellation and transparency, voice separation and recognition, and the ultimate in personalization. All the pieces of the fast-evolving puzzle converging around true wireless earbuds, headphones, hearing enhancement, communications, and unavoidably... hearables. From April 2022 to April 2023, true wireless earbuds and all the surrounding efforts to create product concepts in the hearables class have evolved dramatically. That’s why this year's Market Update article "State of the Hearables Industry" focuses on projecting the evolution and the new possibilities, including all the cutting-edge solutions for low power, battery-powered designs presented at CES 2023.
And because there are so many related developments happening in the audio test and measurement front - many directly motivated by the need to support this exciting technology evolution - this issue of audioXpress also features a report on Headphones Test and Measurement. From the latest ear simulators and couplers to the software that enables manufacturers (or reviewers) to obtain accurate and reproducible test results.
Also as promised, the April 2023 issue of audioXpress brings great articles on audio electronics. And we start with Burkhard Vogel, an expert in the field that many of our readers recognize from his books and magazine articles about tube audio and electronic noise topics. In the previous issue of audioXpress, Marcel van de Gevel wrote a review of Vogel's latest work, titled Slopes and Levels, Spice Models to Simulate Vintage Op-Amp Noise. In this April issue and the next, audioXpress offered the author himself the chance to detail the expanded work addressed in that book. The first article presents the deviations from realistic noise figures in datasheets, based on measurements and calculations for real op-amps, before focusing on the noise source correlations and models themselves next month.
Combining audio electronics with a great DIY approach, Bruce E. Gillingham brings us the first part of his monoblock power amplifier, featuring a novel precision bias controller that he developed. The project is a high-power (300W into 4Ω), bipolar, Class-AB, monoblock amp, featuring voltage feedback, a wide open-loop bandwidth (> 20kHz) approach, and an instrumentation amplifier architecture. This first article details the whole design and the schematics.
Also for DIYers, speaker builder Ken Bird decided to attempt a different approach to the now ubiquitous soundbar, creating a simpler integrated system. Called a Soundbase, the project details an active speaker for those who just want to improve the sound of a TV and increase the height of a TV without a wall mounting. The Soundbase has a built-in two-channel amplifier and subwoofer channel and uses eight Peerless 2" full-range drivers and two 4" Dayton subwoofers.
In another valuable article in his Simulation Techniques series, modeling design expert René Christensen writes about acoustic topology optimization, one of the most interesting new technologies in vibroacoustics. These powerful tools enable engineers to find optimal solutions to problems related to their specific applications and this article presents multiple examples in different areas.
For this month's Sound Control article, Richard Honeycutt writes about the Wrong Things “Everybody Knows” About Acoustics, based on the many misconceptions that he encountered numerous times as an acoustics consultant. Always great to have a reference piece that sets the record straight.
This issue of audioXpress, full of great content, also includes a new part in Chuck Hansen's article series on Power Transformer Parameters, Selection, and Testing. Having detailed the history of transformer cores, their construction methods, materials, testing methods, and their losses, Part 6 focuses on commercial AC power quality, electrical component reliability, and the design of current transformers.
For an enjoyable suggestion, after you finish reading audioXpress, Scott Dorsey reviewed an interesting book written by David Hewitt, one of the many well-known engineers who made history doing live recordings of rock concerts during the 1970s and 1980s - and continued to pioneer this approach to make great recordings of live events. On the Road: Recording the Stars in a Golden Era of Live Music, is an interesting first person testimony of some of the greatest moments in music recording history.
As always, there are more than enough reasons to dive in and start reading this issue. Subscribe if you haven't yet in order not to miss future issues, or renew your subscription, because audioXpress is only going to get better. Subscribing to the digital online version allows immediate access and is available here: audioXpress Subscription Services
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