audioXpress Magazine      September 2020

  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
'Cause Everything Changes
audioXpress' unique role in serving the industry.
Editorial By J. Martins, Editor-in-Chief

Speaker Special Features
26 Altec Lansing's Voice of the Theatre Speakers
What You Need to Know
By Scott Dorsey

Altec Lansing's Voice of the Theatre systems
originally targeted movie theaters. The entire series
was gradually expanded for use in general sound
reinforcement and later converted in extreme high-end
audio segments for hi-fi home use. This article
explains what we need to know about these still highly
sought-after speakers.

32 Loudspeaker Measurements at Home
A Guide for Building Your Own Test Chamber
By Geoff Hill

Like so many builders, designers, and engineers in
these crazy times, Geoff Hill no longer has access to an
anechoic chamber. So how is it possible to still make
useful loudspeaker measurements? In this article, he
explains how to build a basic tetrahedral chamber to
use at home, and then put together a measurement
system and check the results.

38 Fast and Reliable End-of-Line
Acoustic Defect Detection
By Stefan Irrgang and Wolfgang Klippel

This article discusses end-of-line testing, a crucial step
in production, which requires very specific procedures
and measurements. Specifically, the authors focus on
testing irregular acoustic defects (also known as Rub &
Buzz) to reduce the test time, and optimal solutions to
speed automatic testing in a production environment.

44 How Virtual Product Development
Improves the Quality of Consumer and Pro Audio Products
By Alfred Svobodnik and Thomas Gmeiner

This article addresses how modern methods of
acoustical virtual product development make
it possible to assess and optimize quality and
performance problems throughout the entire
product development process. Using a combination
of modeling, simulation, and measurement tools,
everything can be analyzed in-depth before building
the physical product, the two authors explain.

Features
8 The Magnepan LRS
Back to the Future
By Oliver A. Masciarotte and Kent Peterson

For those of you familiar with Magnepan,
its Little Ribbon Speaker (LRS) is a fullrange
quasi-ribbon speaker that was
created to whet your audio appetite.
Oliver Masciarotte provides his opinion
of the speakers, while Kent Peterson
measures its performance.

50 The APR-17 Aperiodic Loudspeaker (Part 2)
Measurements and Final Details
By George Ntanavaras

In the final part of this article, George
Ntanavaras shares the APR-17's crossover
design and discusses the measurements
he took to evaluate the aperiodic loaded
loudspeaker. He also describes a passive
equalizer that he used to boost the
loudspeaker's low-frequency response.

58 The RSX
A Large, Modern DIY Speaker
By Chris Biese

Chris Biese shares his design for the
RSX speakers, which won first place
in the Dayton Audio category at the
2019 Midwest Audiofest hosted by Parts
Express.

Columns
Sound Control
16 From Acoustics to Electroacoustics
The Roots of Early Live-Sound Speakers
By Richard Honeycutt

Audio Scope
22 How Do We Generate
Measured Noise Plots for Op-Amps?
By Michael Steffes

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