As promised, audioXpress August 2023 features an extensive range of topics and offers a great exploration of cutting-edge trends in audio. On the cover of this audioXpress issue is the amazing Mary Flagler Cary Hall orchestral rehearsal room at The DiMenna Center for Classical Music in New York. That is where we had the opportunity and privilege to meet Steve Barber, the creator of the LARES active acoustics systems, the pioneer in the field of Electroacoustic Enhancement and Active Acoustics, now leading the remarkable advancements in this discipline with E-Coustic Systems. An interview and exploration of this state-of-the-art solution in a reference installation is detailed along with a complete overview of Active Acoustics published in this issue also features Meyer Sound's Constellation, Amadeus Acoustics, and L-Acoustics' L-ISA Ambience. Expanding the topic from our previous issue of audioXpress, Philipp Paul Klose writes about Noise Cancellation in Automotive Audio. Is it time to implement advanced Active Noise Cancellation (ANC) into the audio systems of cars? And why is this technology not already in every car? This article investigates how ANC can be beneficial in an automotive application and looks at the challenges in the development phase. It also provides an outlook for applications, products, and the industry adoption.
In Simulation Techniques, René Christensen details the model and possibilities of the SonicEdge transducer - a cutting-edge microspeaker based on a unique MEMS technology that generates sound using active ultrasound modulation. This completely new class of MEMS speaker devices can deliver constant volume velocity across audio frequencies and beyond. The article details how to model the transducer in lumped-element and finite-element acoustic simulations and how to tailor a desired SPL response using acoustic features.
Also featured is the AXPONA 2023 Show Report. As in previous editions, Oliver A. Masciarotte provides an interesting overview of the rooms he visited, the systems he listened to, and what stood out from the Chicago show. Revealing renewed vitality on the Home Audio front, the 2023 edition of AXPONA not only showcased some innovative products, it also drew a more diverse and interesting crowd than in years past.
A major highlight for audioXpress is the visit to the Western Electric vacuum tube factory, which Richard Honeycutt describes in his regular Hollow-State Electronics column. Planned for a long time, audioXpress was finally able to visit the manufacturing facilities of the legendary brand in Rossville, GA. Officially established in 2018, this facility has been continuously producing 300B single-ended triode tubes since 2020 and is already expanding production of other tube models. A visit guided by the entrepreneur responsible for Western Electric's revival, and its current president and CEO, Charles Whitener.
Moving on to Speakers, from a design and development perspective, Jørn Rune Kviserud (Tonalab of Norway) submitted a fascinating exploration of what should be the considerations for Designing a True Midrange Driver. In fact, he offers a 10-point list for the development of midrange drivers. "Many products on the market have met several of these points already, but it is important to note that many of them only work well when combined with other points on the list," Kviserud notes. "The mid frequencies in a multi-way speaker are often handled by a woofer. We are going to look at how one can trade the properties that makes a woofer usable as a woofer and instead end up with a more purpose-built midrange driver."
Also on Speakers, Gary Gesellchen (Vanatoo) offers Part 2 of his Bass Reflex Performance Envelope article, describing a novel approach to estimating the performance envelope available from ported loudspeakers, taking into account port and driver sizes and multiple applicable parameters, and comparison with the performance from a passive radiator. Part 2 expands on the system analysis, showing how driver and port sizes determine how loud and how low a system will play, and how that relates to generally available drivers.
For a DIY approach, this issue offers a high-quality project written by Bruce Gillingham, titled "Instrumentation Amplifier-Based Preamplifier Line Stage." Based on the author's own PA2 Preamplifier, which remains in service since 2002 without any modification other than the addition of two phono preamp modules, this article describes the line stage preamplifier that also includes time-delay-matched, fully balanced (voltage and impedance) outputs and adjustable gain from -51dB to +12dB in precise 1dB steps. All based on the traditional three op-amp instrumentation amplifier architecture, which is seldom used in home audio equipment, even though it has a lot of desirable characteristics for high quality audio.
Finally, there's another chapter of the fascinating article series by Chuck Hansen on Power Transformer Parameters, Selection, and Testing. For Part 10, we continue to test different types of transformers, for leakage flux and external magnetic shielding with both steel and aluminum, core loss sensitivity to the presence of these metals, and measurements of external magnetic leakage fields with distance, with and without shielding.
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