As our readers will notice from the cover, there's a very special report from Thomas Perazella discussing the recent 2022 Speaker Design Competition promoted by Parts Express. After a two-year hiatus due to the pandemic, Thomas was once again invited to be one of the three judges in the Speaker Design Competition, which is normally a core part of the Midwest Audio Fest. Held August 5-6, the event solely focused on the speaker competition, but it was still an amazing event, with new speaker builders from all over the country bringing incredible designs to Springboro, OH, to be appraised, compared, and enjoyed. Read all about the amazing speakers presented at this year's design competition. And on this issue's cover, we are featuring one of the speakers in the competition, the Carl & Stuart Minions by Nick Santorineos.
This issue of audioXpress also offers an extensive Market Update on Wireless Audio technology. In the first of two articles for this report, audioXpress editor-in-chief J. Martins writes about the evolution, the efforts, and the most promising platforms and technologies for wireless audio of the past 10 years. This article focuses on current Bluetooth technology and the transition for audio streaming from Classic Bluetooth to LE Audio. December will include an overview of wireless audio solutions over Wi-Fi and emerging technologies.
audioXpress November 2022 also features articles addressing Digital Signal Processing techniques. The first article comes from Matthew Mitschang (DSP Concepts) and discusses solutions for building Voice User Interfaces at the Network Edge and the role of digital signal processing. Voice interfaces require machine learning and neural computation processors directly on-device. The level of computation for voice processing at the edge requires levels of performance hundreds of times higher from traditional processing technologies. As these edge-AI optimized processors move from the cloud to low-power, always-on devices, they are increasingly used for highly sophisticated audio processing in applications from earbuds to automobiles.
Next up, Dave Betts, the Chief Science Officer at AudioTelligence, discusses the merits and challenges of using beamforming and blind source separation techniques to correctly process voice sources from the audio signals picked up by microphones in real-world situations. This valuable article explains how these signal processing techniques can help deal with the noises that make it difficult to pick out and clearly hear voice, and how to obtain clean audio signals picked up by microphones contaminated with interference, noise, and reverberation.
This month's Sound Control article by Richard Honeycutt revisits a topic that was motivated by an enquiry about smartphone apps for measuring sound pressure level (SPL). This is a topic that was originally addressed in some Sound Control articles published in audioXpress back in 2015. But Richard Honeycutt realized that information could be outdated and his research verified his suspicions. Turns out that more recent studies have also been done, some new apps are available, many devices no longer have a 3.5mm jack, and older apps are no longer offered. This article provides an updated look at the solutions currently available as audioXpress prepares to explore the latest software and apps for sound measurements.
Also featured in this issue are two essential articles on power supply design for high-end audio systems, and selecting and testing power transformers. The first topic is the second article by electronics audio expert Frans de Wit, where he considers all the factors and design options for a high-quality power-supply especially targeted toward preamplifiers, record players, and other low-power appliances. Expanding on the topic, in this continuation he performs simulations that demonstrate the real improvements that can be achieved.
The next article starts a new series by esteemed audioXpress author Chuck Hansen, who wrote what is probably the most comprehensive work on Power Transformers and its Parameters, Selection, and Testing for audio electronics. Based on his extensive experience in the design and specification of current transformers, including designing specialized test fixtures for a large aerospace contractor, in this issue Chuck explores ideal transformers, magnetic core materials, variations in properties, and cost factors for magnetic materials.
And speaking of transformers, Scott Dorsey spent the summer in Europe visiting companies in the Scandinavian region, and had the opportunity to visit the Lundahl Transformers factory, located in the small town of Norrtälje, just outside Stockholm, Sweden. The article reviews the company's interesting and unique history as of one of the most respected manufacturers of high performance transformers for audio applications. In the exclusive factory Tour, Scott was able to see how Lundahl makes those great transformers and shares some insights in conversation with Per Lundahl.
Finally, this month's Hollow-State Electronics article explores the history and operation of Voltage Regulator (VR) Tubes in Audio Amplifiers. These are not really vacuum tubes, as they are filled with a gas such as argon, or a mixture of gases. Not common today, these unusual tubes certainly added extra visual excitement, but the original reason why they were used in audio was to allow battery-operated radios to be used without expensive batteries of limited lifetimes. A great read to conclude this issue of audioXpress available in digital and in print.
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