audioXpress Magazine      March 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
Meeting The Standards
UWB high-resolution low-latency audio interface.
Editorial By J. Martins
Audio professionals working in product development, design, manufacturing, and system implementation always meet new challenges as technologies change and evolve. In professional or consumer applications, digital audio signals are being carried using a number of different platforms, technologies, and digital protocols, creating a complexity that no single company in the test and measurement (T&M) field is able to address on its own. Increasingly, T&M companies specific to the audio industry are being forced to focus on one specific angle (e.g., electronics product design, acoustic measurements, production line testing, etc.). On the software front, things look a bit more dynamic, with the availability of solutions that are more or less able to react quickly to new industry demands.
---> From The Editor's Desk: Meeting The Standards.

5 Supporting Companies

Features
32 A Look Inside Douglas Self's Small Signal Audio Design
By Jan Didden
After spending some time with Douglas Self's latest
book, our audioXpress technical editor provides his
refreshing take on this detailed small-signal audio
design tome.

34 The AVM-100 True-RMS Voltmeter
By George Ntanavaras
Learn how to build your own AVM-100 True-RMS
Voltmeter with a large analog moving coil meter to
indicate the measured voltage like the old-fashioned
voltmeters of the previous century.

44 The Second Harmonic Distortion Myth
By Uli Brüggemann
This article introduces a diversity of thoughts about
the myth of second harmonic distortion, how second
harmonic distortion sounds, and why people prefer it.
From perception to math.

50 Improving The Transfer Function Of Electrodynamic Loudspeakers
By Reinhold Lutz
This article reviews and compares motion feedback
technologies proposed or used to achieve a nearly
perfect electro-acoustic transfer function, including a
detailed control strategy of different types of sensors.

56 Hearing and Audio Part 1 — Frequency, Phase, And Time
By Milind N. Kunchur
This two-part article series addresses controversial
issues surrounding high-end audio and provides
insights into the sophistication of the human hearing
process. These concepts furnish a more enlightened
backdrop for managing expectations, as to what
might or might not matter for reproducing music to
the highest fidelity.

Audio Test & Measurement
Market Update
8 Evolution In Hardware And Software
By J. Martins
This market update offers an overview of several of the
latest software and hardware solutions for audio test and
measurement introduced in the past year.

20 Listen SoundCheck And AmpConnect 621 Audio And Acoustics Test Suite
Flexible Audio Testing For Pros
By Rens Tellers
When Listen, Inc. released SoundCheck 21, the latest
version of its flagship audio test software, audioXpress
scheduled this review. The experience also allowed us to
try out the latest Listen AmpConnect 621 USB-controlled
multichannel audio test interface.

26 Room EQ Wizard (REW)
Looking Back On Audio Measurement Software History
By Philipp Paul Klose
Discover how, within the last 20 years, Room EQ Wizard (REW)
has evolved from a problem solver to a comprehensive set of
useful tools bundled in a free software package. Professionals
and enthusiasts now use the application every day.

Columns
Hollow-State Electronics
61 The History of Ampeg Musical Instrument Amplifiers
By Richard Honeycutt
This article revisits the beginning of Ampeg's musical
instrument amplifiers and details how they have evolved
to present day.

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