Our October 2023 issue expands the audioXpress promise of delivering the best content on the fascinating path towards great audio product development. This issue combines a strong lineup of articles about speakers, but also many other topics.Starting with our visit to Dutch & Dutch, Jan Didden unveils the journey of this innovative speaker manufacturer from The Netherlands. This company, founded in 2014, has so far achieved remarkable success with a single product designed to break the vicious cycle of speakers and room acoustics. The Dutch & Dutch 8c is a no-compromise active speaker designed to work together with the acoustics of the listening room. The 8c is also a complete digital audio streaming system praised for good reason. Jan Didden asked Martijn Mensink, the company's founder, to explain his philosophy of design.
And from the expert hands of Reinhold Lutz (AudioChiemgau), this issue discusses how to measure loudspeaker SPL response and harmonic distortion at low frequencies in a standard environment, full of reflections from acoustically hard boundaries (e.g., walls, floor, and ceiling), room resonances, and even ambient noise reducing the dynamic range and accuracy of the measurements. The article details a method combining near-field measurements with two identical microphones.
And the principles described in Dr. Reinhold Lutz's article are applied in a solution called the Mode-Compensator for precise measurement of the sound pressure frequency response in the presence of room modes, available from the author's company, AudioChiemgau. Jan Didden and Rens Tellers did a basic functional test with the ModeCompensator to find out how well they could make it work and they were pleasantly surprised with the results.
Of course, this speaker focus issue also offers the best in DIY. First, with an amazing open baffle design by Perry Marshall: The Bitches Brew Live Edge speakers. Highly praised at the 2022 Speaker Design Competition sponsored by Parts Express, these large dipole speakers named after the classic Miles Davis 1970 album have surprised for the stunning imaging and 120dB dynamic range, as well as its simplicity and elegance. The article describes the full three-way system construction made from book matched slabs of spalted sycamore with a natural finish and uses two SB Acoustics 15OB350 woofers and the B&C Speakers 15CXN88 constant directivity horn coaxial. Perry Marshall has designed speakers for 40 years, and this “ultimate design,” as he describes embodies the very best of what he learned.
Another great DIY project concludes in the issue, with the second part of "Building A Minimally Baffled Dipole Loudspeaker" by Charlie Laub. The first article discussed the theory, design, and construction of an open baffle loudspeaker. In this second article, Laub measures the drivers, details the crossover design, voicing equalization, and a practical example he built. Charlie Laub's Baffle-less-ness, the author’s four-way system open design, won first place in the 2022 Speaker Design Competition’s Open Unlimited category.
Moving away from speakers, in January 2022, Western Electric started taking orders for its new 91E integrated amplifier, following the resumed production of the 300B triode tubes at the modern Rossville Works facility. audioXpress already published the definitive review of these 300B new-generation tubes, in its May 2022 issue. In this October 2023 issue, Richard Honeycutt shares his listening impressions of the modern 91E, while revisiting the history of this venerable single-ended amplifier and its long-running legacy of quality sound.
And from our esteemed contributor Ethan Winer, this issue of audioXpress adds another unique project, this time jumping straight to the beginning of the audio chain - the microphone. In the Popping P Filter, Ethan Winer describes an original circuit that effectively removes the low-frequency impulses caused by air blasts from a person speaking or singing into a microphone, as well as "plosives." This analog circuit removes these irritating sounds from a live audio stream in real time, directly at the source. This original circuit is offered for free for non-commercial use, and Ethan Winer is open to licensing offers for commercial manufacture.
In his Sound Control column, Richard Honeycutt explores Passive Variable Acoustics. Because everything depends upon the purpose of a venue, where room size, reverberation time, and provision of beneficial early reflections must be considered, varying those acoustic parameters allows accommodating different types of performance and events. Passive variable acoustics use one of two methods to vary the RT and its frequency dependence: changing the cubic volume of the room or the total acoustical absorption.
And the October 2023 issue of audioXpress also wraps up the article series on Power Transformer Parameters, Selection, and Testing, a remarkable work by Chuck Hansen. The 12th article concludes his comprehensive examination of transformer cores, construction methods, materials, testing methods, commercial power quality, and design. This final part expands the transformer tests and closes with important considerations for audio designers.
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