The September edition of audioXpress is our always popular Speaker Focus issue, as loudspeakers and speaker building are at the core of this publication. And that's precisely why we start with a complete Market Update on "Speaker Design and Testing Tools," where we revisit some of the tools that speaker designers, developers, and DIY builders have at their disposal, from free software to the latest hardware, from a home bench and R&D to production line testing. A great overview that offers a broad perspective for those who depend upon those tools for their work or passion.
And featured prominently on this issue's cover, Michael Kastner offers a detailed description on the "Design and Development of the Holoplot X1 Matrix Array." Headquartered in Tempelhof, Berlin, Holoplot is a company on a mission to transform the audio industry. In 2021, it launched the X1 Matrix Array - a product that has introduced a whole new category of sound system, extending from two already existing landmark innovations in pro audio - the line array and electronic beamsteering - to provide control of sound in both horizontal and vertical axes through a matrix of loudspeaker drivers. The X1 Matrix Array is Holoplot's software-driven and hardware-enabled effort to enable ultra-precise control over sound propagation and localization, while also enabling individual and independent sound beams, able to reproduce differing content at the same time.
This intense R&D journey is told from the company's perspective, including testimony from its renowned engineers who have joined this unique industry effort. As audioXpress editor-in-chief J. Martins states in this issue's editorial, "...when audioXpress writes about speaker innovation, we value and recognize as much the journey and the strategy, as we value the technology, the patents, and the 'success'."
And continuing with unique R&D Stories that we are certain our readers will be excited to read, Zami Schwartzman shares his personal journey to design and perfect "Motion Feedback Desktop Subwoofers for Nearfield Studio Monitors." For this project, the author perfected his own accelerometer-based motion feedback designed fully assembled plate amplifiers with MFB control, crossover and voice coil thermal protection that can be matched with any low frequency MFB driver. After experimenting with motion feedback to create a subwoofer to extend the response of its electrostatic speakers, which included its own unique capacitive position sensor to feed the feedback loop, the author successfully explored the concept of desktop subwoofers to extend the response of compact studio monitors. The proof of concept demonstrated the ability to perfectly complement popular active nearfield monitors, mitigating the effects of room reflection. And, Schwartzman is now open to exploring all licensing or product engineering opportunities.
For the next article, audioXpress asked Geoff Hill, the inventor of the Tetrahedral Test Chamber (TTC), a member of the international Electrotechnical Commission’s standards 60268-21-2018 and 60268-22-2020, and part of the IEC Working Group TC 100/TA 20/PT 60268-22 on electrical and mechanical measurements on transducers to comment about the evolution and work in progress happening on loudspeaker measurement standards. In the first of two articles "Replacing IEC 60268-5: What Comes Next and Why," he summarizes the progress taking place in a perspective that appeals directly to all loudspeaker designers and manufacturers.
And from speakers to automotive audio, audioXpress reviews the recent - and very successful - AES 2022 International Conference on Automotive Audio that took place in Dearborn, MI, and which also featured a full track of events promoted by the AES Audio Product Education Institute (APEI). This report, written by Roger Shively, the AES conference Chair, reviews the most important presentations topics discussed and the exciting demonstrations by companies such as Dolby, Fraunhofer, Dirac, Tymphany, and DSP Concepts, among many others.
Expanding on that coverage, Christoph Sladeczek (Fraunhofer IDMT) writes about "Audio Objects as Platform Technology in Vehicles," one of the key presentations that took place at that June 2022 AES event. With the emergence of immersive entertainment and personalized sound staging for automotive audio, the article describes a new workflow comprising the rendering of audio objects, for the production and tuning process, as well as the implementation on resource-limited hardware. Since the object-based audio is independent of the loudspeaker setup, this significantly reduces the complexity of the tuning processes for car manufacturers. Essential reading for those working directly in automotive platforms, but also for those working with object-based spatial audio implementations.
For our DIY section, audioXpress invited author George Ntanavaras to revisit his popular Double-Dipole Subwoofer, which was originally published in 2004. Like many speaker projects published in Speaker Builder or the first years of audioXpress, we find concepts and designs that are still being built today and frequently referenced. That is the case with the “Double-Dipole Subwoofer," which first appeared almost 20 years ago and deserved to be revised and republished. Ntanavaras made some corrections and clarifications to the original project, and submitted improved figures. The article is also now published with the original color photos.
And for our readers looking for more of the best in audio electronics - and tube circuits - Richard Honeycutt offers an interesting read in his Hollow-State Electronics column. In this article, he compares the LTSpice-modeled performance of the original 300B Triode Single-Ended Push-Pull (Western Electric 91A), and a 6CA7 (EL34) push-pull power amp with no overall negative feedback.
A very strong issue of audioXpress with valuable articles and the best in DIY. A lot to explore now and many times later. Remember, every month, audioXpress brings innovations in audio, different topics in audio electronics, and the best in DIY audio, published 12 times per year, and available in print and online.
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