audioXpress Magazine      June 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.

Comment
4 From The Editor's Desk 
A Glimpse Of The Future, Inside A Car
Editorial By J. Martins, Editor-in-Chief

5 Client Index

Columns
Sound Control
32 Using Line Arrays to Control Directivity
By Richard Honeycutt

Features
38 KEF LS50 Meta Loudspeaker
An Material Improvement
By Oliver Masciarotte and Kent Peterson
In 2020, British brand KEF updated its extremely
popular LS50 speaker design and introduced the LS50
Meta, an improved version of the original LS50 passive
design. Here, Oliver Masciarotte reviews the updated
speaker and Kent Peterson provides the measurements.

48 Measuring Vibration with Piezoelectric
Sensors (Part 3)
The Piezoelectric Amplifier
By George Ntanavaras
In this article series, George Ntanavaras describes his
research on measuring vibration using Piezoelectric
Sensors. In the third and final part of this article
series, he describes the design and construction of the
piezoelectric amplifier and presents the measurements
he took to evaluate the system.

56 Noise Is Everywhere — Even In MC Input Transformers (Part 2)
Additional Proof for Skeptics
By Burkhard Vogel
In this article, Burkhard Vogel demonstrates that
it is good practice to measure a transformer with
an input load, and that a MC step-up transformer
(SUT) produces noise because of its insignificant but
non-zero impedance. He concludes his article with
a step-by-step approach to noise measurements,
simulations, calculations, and conclusions.

62 The Science and Physics of High-End Mic-Preamp Design (Part 5)
The Best Practice
By Mike Meechan
In the previous articles, Mike Meechan considered the
physics that play a fundamental part in microphone
pre-amplifier design, explored its inhabitance in the
real practical world to retain the fidelity of the mic
signal along its path from transducer to output, and
looked at what (theoretically) contributes to perfect
active mic preamps. He concludes his article series
with the golden rules of low-noise, mic preamp
design.

68 Class-D Amplifier Output Filters
For Next-Generation Audio Devices
By Rien Oortgiesen
As consumers demand even more audio performance
in ever-smaller packaging, Infineon's new MERUS™
family of Class-D amplifiers uses an innovative
multilevel technology to deliver new levels of efficiency
across the whole audio frequency spectrum while
significantly relaxing the requirements for filtering.
These improved efficiency levels open up new
possibilities for the audio system designer.

Automotive Audio Solutions
8 Tech for the Automotive Framework
By J. Martins
In this brief Market Update we focus our attention on a few key technologies, platforms,
and innovations that should be on every developer's radar when working on automotive
audio projects. Audio solutions that are transversal to the vehicle's design and human
interface.

20 The Changing Automotive Environment in 2021
By Roger Shively
This update on the automotive audio
industry discusses what is new in the
user interface to the audio system, how
cockpits are changing, and the approach
to optimizing them for the end user's
audio needs. It also looks at how audio
systems are changing and examines
new challenges for OEM audio system
designs and how they are being met.

28 Vehicle Electrification And Active Noise Cancellation
The Driving Forces Behind Innovation
in Future In-Vehicle Infotainment
(IVI) Systems
By Krunal Maniar
This article examines noise sources
in automobiles and discusses various
noise cancellation technologies to
better understand the future of sound
management in car audio systems. 

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