audioXpress Magazine      January 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.

Editorial: The Things That Stand Out
As we start a new year for this publication, it's time to offer some perspective
about the things that inspire us for 2024.
Editorial By J. Martins
Following my previous reference to the Urbanista Malibu, the world's first self-charging wireless speaker using an integrated Powerfoyle membrane that charges the battery whenever exposed to indoor or outdoor light, Exeger, the developer of the Powerfoyle technology, is now top of mind for 2024. We will attend Exeger's press conference, selected to be part of the Official CES 2024 Media Days, which is in itself a significant honor and a sign of the impact this Swedish company is having on the technology world. Exeger has also announced a strategic partnership with Tymphany, one of the largest OEM / ODMs of speakers and audio systems in the world, to produce a self-powered speaker that will be unveiled at CES 2024.
---> Editorial: The Things That Stand Out.

5 Supporting Companies

Features
20 Loudspeaker Bass Reflex Alignments
By Claus Futtrup
This article describes the evolution of enclosure
designs based on electrical filter theory, and includes
the concept of an alignment chart.

30 TPCD Technology In Headphones
Engineering To Control Diaphragm Resonances
By Martin Turesson
Thin-ply carbon diaphragm (TPCD) technology,
pioneered by Composite Sound, tries to control the
negative effects of resonances rather than trying
to reduce them. Now, the company is entering the
over-ear headphone market with the TPCD diaphragm
technology, enabling headphones with better sound
quality, improved bass performance, and higher
sensitivity.

38 An Afternoon With Robert Munnig Schmidt
By Jan Didden
What do motional feedback, silicon wafer steppers,
voice coils, and Class-D amplifiers have in common?
Everything, as far as Prof. Ir. Robert Munnig Schmidt
is concerned. audioXpress Technical Editor Jan Didden
decided to find out why and interview the man known
as “mister motional feedback.

46 The Role of Resonance In Audio Clarity
By Roger Tall
Years of research have shown that resonance from the
body of a capacitor in a loudspeaker crossover circuit
has an audible impact on sound quality. This article
details the extensive testing, measurements, and
conclusions, which allowed perfecting a manufacturing
process minimizing resonances in capacitors.

50 Composite Amplifiers
By Paul Marchese
This article presents a fairly in-depth analysis of
composite amplifiers, including the effects of local
as well as global feedback. In his exploration, the
author looks at stability in detail and debunks a few
rules of thumb, before applying clever measurement
techniques to measure the very low distortions.

58 Is Digital Jitter Really A Problem?
By Ethan Winer
Since the dawn of the digital era decades ago, the
timing error known as "jitter" has been accused of
harming audio fidelity in A/D/A converters. In this
article Ethan Winer explains what jitter is, what
causes it, and — most important — lets you hear jitter in
controlled amounts so you can decide for yourself how
damaging it really is.

Market Update — Drivers and Transducers
8 New Options For Improved Designs
By J. Martins
From home speakers to high-end speakers, from soundbars to subwoofers, the world of
transducers continues to evolve mostly outside of the spotlight, with crucial innovations
occasionally breaking through. audioXpress highlights those that stand out.

Columns
Hollow-State Electronics
62 How Can I Learn?
By Richard Honeycutt
Learning about hollow-state electronics used to be as easy as DIY trial-and-error, getting
information from a family member or friend, or reading technical books and magazines
such as Popular Electronics. Even today with all the information available online, finding a
knowledgeable and patient mentor and lots of practice still seem to be key factors.

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