audioXpress Magazine      August 2021

  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.

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4 Editorial: Making Acoustics Personal And Safe
Acoustic science is where everything starts, determining how sound and audio systems behave in practice.
Article By J. Martins, Editor-in-Chief

Features
44 Audio Precision APx517B Acoustic Audio Analyzer
True Turnkey Audio Measurements
By David Logvin
The Audio Precision APx517B Acoustic Analyzer
debuted at the end of 2020 as a solution specifically
built for the production-line testing of speakers,
microphones, headphones, headsets, and the wide
range of consumer electronics incorporating speakers
and microphones. In his review, David Logvin explores
audio measurements with this fully integrated
hardware with digital interface options and accredited
calibration.

52 Parameter Estimation And Box Simulation With Speakerbench (Part 1)
Model Parameter Comparisons
By Claus Futtrup and Jeff Candy
In this two-part article series, Claus Futtrup and Jeff
Candy investigate leakage loss as identified with
an advanced transducer model and verified with
measurements. This test is compared to classical
Thiele-Small modeling with the intention to motivate
the reader to further explore advanced parameter
estimation and box simulation with Speakerbench,
which is presented in Part 2.

56 The DH-220C MOSFET Power Amplifier (Part 2)
Construction and Testing Instructions
By Bob Cordell and Rick Savas
This reference DIY project describes an upgrade
construction project for the legendary Hafler
DH-220 lateral MOSFET power amplifier, but it can
also be used to upgrade other Hafler models or
even inspire new designs. In Part 1, the authors
discussed the design and performance of the DH-220C
upgrade amplifier. Here in Part 2, they describe the
construction and testing details.

62 A New Type Of Amplifier For Direct Driving Loudspeakers (Part 2)
Feedback and Power
By Paul Marchese
In Part 2 of this article, Paul Marchese takes a brief
look at magnetics — EMFs and questionable modeling —
and comes up with a practical feedback network on
the voltage feedback side. Then, he examines the
power delivered to a fairly accurate loudspeaker
load and the non-ideal effects of a real-world power
amplifier as well as variations of the VSCS design.

Focus on Acoustics: Market Update
8 Acoustical Solutions Round-Up 2021
A Growing Awareness of Acoustics!
By J. Martins
This article highlights some new products and designs,
while also discussing the progress made in new first-approach
acoustical treatment products. Because they are essential in
understanding acoustics, the article also discusses planning,
simulation, and measurement tools.

22 Acoustic Room Treatments
Taming the Gorilla
By Thomas Perazella
People can get so wrapped up in the details of a project
that they miss a major factor, affectionately called the
800-pound gorilla in the room. That is true in audio as well. But
for good sound reproduction in a home environment, that
factor is the room itself. Thomas Perazella shares his journey
in room treatment for a dedicated space in his new home.

32 An Introduction to Measuring Rooms
By Ethan Winer
Before you start measuring and playing around with your
new speakers, maybe you should know your room. This
article explains the importance of understanding the
acoustics of our own listening rooms and how a proper
measurement will help us with that essential knowledge.

Columns: Sound Control
40 Zooming Toward Better Online Audio
By Richard Honeycutt

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