audioXpress Magazine      October 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.

From The Editor's Desk
4 Home Theater And Home Entertainment
This issue has a balanced mix of content addressing
audio electronics knowledge, technology reviews and more.
Editorial By J. Martins

5 Client Index

Features
8 USound Megaclite 4.0 UH-R2040 MEMS Earphones
By Brent Butterworth
The Megaclite 4.0 UH-R2040 is a reference design
intended to prove that MEMS drivers can work well in
a standard earphone design. Brent Butterworth listens
and measures to see if this new technology from
USound is ready for the market.

28 The Complete Linear Audio Library On USB
Reviews by Gary Galo, Bob Cordell, and Dimitri Danyuk
Linear Audio, the bookzine created in 2010 by Jan
Didden, is now available on a USB with The Complete
Linear Audio Library. We asked three Linear Audio
and audioXpress authors to review it and share their
thoughts.

38 Ultra-Linear: Why It Works And When It Will Not (Part 1)
The Fundamental Questions
By Morgan Jones
This article reviews the story and the principles of
ultra-linear electronic circuits, looking in detail at
several tube types. This article is the first in a two part
series in which Morgan Jones not only shows how
ultra-linear works, but more importantly, predicts
when it won't.

44 Cascodes, Folded Cascodes, And Current Mirrors (Part 1)
Cascodes And Folded Cascodes
By Morty Tarr
Cascodes, folded cascodes, and current mirrors are
circuit topologies that are used to provide specific
functions for an amplifier design. These topologies
improve the performance of the devices, but also
add complications. In this first article, the author
discusses cascodes and folded cascodes.

50 Refurbishing Altec Lansing Vintage Speakers
By Bruce Heran
This article showcases how refurbishing these
highly coveted speakers continues to be a rewarding
experience.

56 The Tetrahedral Test Chamber Story (Part 2)
Consistent Loudspeaker Measurements
By Geoff Hill
In Part 2 of his article, Geoff Hill describes the initial
launch and refinement phase of his Tetrahedral Test
Chamber (TTC), proving the chamber's measurement
repeatability, and detailing its inclusion in the
international standards.

Market Update – Home Theater
14 Raising The Bar On Residential Entertainment
By J. Martins
This article focuses on home theater and residential
installation technology and solutions, with the goal to
project the market trends going forward. It addresses both
the products that appeal directly to the consumer, and
installation-oriented solutions for home entertainment.

Sound Control
32 A Tale Of Speakers In A Room
By Richard Honeycutt
Richard Honeycutt shows us why understanding the
strengths and weaknesses of different speaker designs
and modeling/comparing the best candidates will
ultimately lead to the best results for any space.

Hollow-State Electronics
60 Effects Of Negative Feedback
By Richard Honeycutt
In this Hollow-State Electronics article, Richard Honeycutt
uses LTSpice modeling to determine how different amounts
of negative feedback affect the output from a hollow-state
power amplifier.

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