audioXpress Magazine      April 2023

  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.

4 From the Editor's Desk: New Frontiers In Wireless
Working in audio technologies has never been more exciting.
Editorial By J. Martins
Often I find myself explaining why I remain optimistic and enthusiastic about what we do at audioXpress and the audio industry overall, particularly to those who insist that the "good old, golden days" are behind us and/or that "nothing is as it used to be." At the beginning of the year when I returned from CES full of energy and inspiration, I repeatedly heard the same statements, "...but, there were hardly any audio companies left at CES!" And that's the reason why I explain—and strongly recommend — not to limit one's perspectives. That's why I need to get out there, and follow the many professionals in the audio industry who are thriving and living the "golden days" while others are just starting. Yes, nothing stays the same. Things evolve and in a world of technology, that's precisely what you would expect.
---> New Frontiers In Wireless.

5 Supporting Companies

Features
28 Remote Recording In The Rock Era
David Hewitt's On the Road
Review by Scott Dorsey
There were many well-known engineers who made
their livings doing live recordings of rock concerts
during the 1970s and 1980s. One of the most popular
engineers was David Hewitt, who wrote a book about
his experiences. After a thorough read, Scott Dorsey
shares his review of the book.

32 Acoustic Topology Optimization For Vibroacoustics Applications
By René Christensen
Acoustic topology optimization is one of the most
interesting new technologies in vibroacoustics, and is
a powerful tool that enables engineers to find optimal
solutions to problems related to their applications.
In this article, several acoustic topology optimization
examples are shown.

40 Vintage Op-Amp Noise Simulation
Part 1 — Deviation From Realistic Noise
Figures in Datasheets
By Burkhard Vogel
This article is divided into two parts. Part 1 presents
the deviations from realistic noise figures in
datasheets, based on measurements and calculations
for real op-amps.

46 Monoblock Power Amplifier With Precision Bias Control
Part 1 — The Design
By Bruce E. Gillingham
The project described here is a high-power (300W
into 4 Ohm), bipolar, Class-AB, monoblock audio power
amplifier. The design utilizes voltage feedback, a
wide open-loop bandwidth (> 20kHz) approach, and
an instrumentation amplifier architecture. It also
features a novel precision Bias Controller that the
author developed.

56 Building A Soundbase
By Ken Bird
One of the most successful speaker categories today,
soundbars were originally intended to compensate
for the poor sound quality of thin-display TVs. This
project takes the concept up a notch in sound quality
and fidelity for any living room application.

62 Power Transformer Parameters, Selection, And Testing
Part 6 — Quality, Reliability, and Design
By Chuck Hansen
The initial group of articles 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.

Market Updates
8 State Of The Hearables Industry
By J. Martins
From April 2022 to April 2023, true wireless earbuds and
all the efforts to create product concepts in the hearables
class have evolved dramatically. That's why this year's article
focuses on projecting the evolution and the new possibilities.

20 More Choices For Headphones Test & Measurement
By J. Martins
This article is a brief update on test and measurement
solutions for headphones and earphones that we couldn't
fit in our March 2023 issue. An update on solutions that
perfectly complement our hearables-focused article.

Columns
Sound Control
36 Wrong Things "Everybody Knows" About Acoustics
By Richard Honeycutt
Our acoustic expert sets the record straight about some of the more common
misconceptions about acoustics that he has heard over the years.

30 New Microphone Technology
— Flat Response Curve, Set Sensitivity
By GRAS Sound & Vibration

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