audioXpress Magazine      April 2024

  audioXpress remains the authority on audio and reproduced sound by connecting manufacturers and distributors with developers, buyers and consultants around the globe! It's readers are the audio product designers, consultants, integrators, DIY enthusiasts, opinion leaders and your best customers. All of them agree that the coverage of trending topics, unique in the audio industry, make audioXpress a must read.

Every month, audioXpress combines the best educational articles on topic such audio electronics, speaker and headphone design, amplifiers (from tube to Class D), acoustics, practical test and measurement, audio engineering praxis, and standards. audioXpress provides inside stories on new audio developments, on R&D Stories, the most complete objective reviews of innovative products and software, and selects some of the best DIY audio projects from worldwide experts.

From the Editor's Desk
Doesn't Look Like It
The disruption will come from technology.
Editorial By J. Martins
While researching for this year's Earbuds and Hearables State of the Industry Market Update — a category that converges pure listening enjoyment and communications with hearing assistance and augmentation — I had to carefully review the results thus far from the much propelled over-the-counter (OTC) hearing aid policy, which was supposed to drive down costs, increase access, and open up a market space for innovation in hearing aids. And unfortunately, it seems that companies are basically using that ruling to launch products that are more basic hearing aids that allow self-fitting but still look like hearing aids, and do less than the "medically prescribed" hearing aids. A few exceptions from innovators such as Eargo made us believe that something could change, gradually.
---> Doesn't Look Like It.

5 Supporting Companies

Features
38 An Afternoon With Menno van der Veen
By Jan Didden
Menno van der Veen has made a name for himself
in the world of high-performance power and tube
output transformers. He is also the founder of
the TubeSociety, where he teaches the design,
construction, and testing of high-end tube amplifiers.
audioXpress visited van der Veen for this interview
in his home, in the flat lands of the north of The
Netherlands.

44 A High-Performance 60-Watt Class A Amplifier
Part 1 — Amplifier Design
By Andrew C. Russell
This project, named the ax-Amplifier, uses Augmented
Feedback Error Correction (AFEC) to achieve ultra-low
distortion and improve key audio performance
parameters without adding too much complexity and
cost. Published in two parts, this article details the
amplifier's design, with Part 2 discussing the power
supply system and conclusion with measurements.

54 Comprehensive AC Power Controller
By Thomas Perazella
To obtain maximum performance from your AC-powered
equipment and extend service life, several
potential problems of typical mains power must be
addressed. This article describes an AC mains power
controller for that purpose.

64 Hearing And Audio Part 2 — Auditory Resolution
By Milind N. Kunchur
Our hearing, the conversion of sound into neural
signals and the processing of these signals, is much
more complex than many of us realize. The two-part
article series addresses music reproduction
and fidelity in that perspective. This second article
addresses issues of resolution, detectability, and the
consequences for blind testing.

Hearables
Market Update
8 Earbuds And Hearables State Of The Industry
By J. Martins
True wireless hearing devices are changing the way we
listen to content, communicate, and perceive the world.
The evolution toward hearables continues to encourage
innovation in what is currently the most successful product
technology segment.

22 Microphone Array Beamforming With Optical MEMS Microphones
By Michael Tuttle and Jakob Vennerød
Microphone arrays are widely used to improve far-field audio
capture. This article describes how the sensiBel 80dB SNR
optical MEMS microphone provides significant performance
benefits for three main types of microphone array beamforming
algorithms.

32 Unveiling The Impact Of Ear Canal Geometry
for In-Ear Headphone Testing
By Brian Johansen, Per Rasmussen, and Morten H. Pedersen
Frequency response is not the only important factor in testing
in-ear headphones. In this article, the authors conducted
simulations to assess the pressure field and its impact on
different ear canal geometries.

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