Speaker Box Alignments from Numerical Optimization - The Quasi-Chebyshev Alignment

After seeing many speaker designers returning to trial-and-error approaches that seem to forget the historical work and analytical approach, Lars Risbo decided to explore numerical optimization to synthesize attractive alignments both for reflex and passive radiator box types. This reference article basically expands on Claus Futtrup's "Loudspeaker Bass Reflex Alignments" article series published in audioXpress, and expanded with dedicated articles in Voice Coil.

In this December 2024 issue there's a new DSP product review of the Marani Pro Audio MIR260A outboard processor, and Lars Risbo shares his expertise in Numerical Optimization applied to Speaker Box Alignments. Essential resources are the updated directories of Test and Measurement and of Simulation and CAD Software vendors. On Test Bench, Vance Dickason characterizes the Faital Pro HF110 1" Neodymium Motor Compression Driver and the SB Acoustics Satori MR16TX-8 6.5" TPCD Midrange.

There's a new Danish hifi speaker brand in the market, part of the expanding audio universe created by Peter Lyngdorf, the founder of HiFi Klubben, and co-founder of Purifi Audio. The project was inspired by Henrik Reinholdtsen, the CEO of Nordic Hi-Fi, a direct-to-consumer business that is also part of the HiFi Klubben universe. Radiant Acoustics is now on the market with the Clarity 6.2 passive speaker, using a 6.5" Purifi woofer and a new AMT tweeter, with a custom-designed waveguide, developed by Lars Risbo.

The PTT6.5M08-NFA-01 6.5" Midrange is the fourth woofer from Purifi Audio to be examined in Test Bench. This midrange is pretty much identical to the previously examined PTT6.5X and PTT4.0X woofers, and includes the same constant Sd surround, cone edge stiffening ring, and low magnetic hysteresis motor design. However, the PTT6.5M08-NFA-01 is optimized to have higher efficiency (91dB at 2.83V8/1m) for use with multiple woofer three-way design configurations. This article was originally published in Voice Coil, January 2023.

This Test Bench addresses Purifi Audio’s PTT4.0X04-NFA-01 4” midbass, which is very similar to the PTT6.5X reviewed in Voice Coil July 2021, and includes the same constant Sd surround and low magnetic hysteresis motor design. The distinct cone assembly for this driver consists of a flat profile paper cone made with a proprietary fiber mix, a concave dust cap that covers about 90% of the cone surface, plus the addition of a V-shaped edge reinforcing ring glued around the outside rim of the back side of the cone. Compliance is provided by a unique NBR surround, which as in the PTT6.5X surround, deserves to be explored, motivating Vance to discuss it with Purifi’s co-founder Lars Risbo.

We looked at the most-read articles of 2021 in audioXpress.com (including selected articles from Voice Coil magazine), and we created this Top 10 list of news stories and online articles. 2021 expanded slightly on the record-breaking year that was 2020 for audioXpress.com, in terms of number of visits and regular users of the website. Visitors from all over the world returned more often to read the more than 7,700 stories available. Which of the topics and stories published online in 2021 were the most popular? Here are the results!

The Purifi Audio PTT6.5X04-NFA-01 midbass transducer is an over-achiever, and to help understand why, Dickason talks with Lars Risbo about the research and thought process that lead to many of the features found in this woofer. Including the unique cone assembly that consists of a mildly curvilinear paper cone made with a proprietary fiber mix, a 3.13” concave dust cap, and a V-shaped edge reinforcing ring, the NBR surround, and what Dickason calls "probably the most unique surround in the history of Voice Coil’s Test Bench. This article was published in Voice Coil July 2021.

It's time for Loudspeaker News and Developments, unique technology Spotlights, valuable industry Directories, great speaker patent reviews, and Vance Dickason's speaker driver characterizations in Test Bench. This month, Bruno Putzeys and Lars Risbo write about their speaker research for Purifi Audio, James Croft reviews an acoustic low-pass filter patent awarded to Bujeon, and Vance Dickason tests the 5CXN44 coaxial driver from B&C Speakers. This edition features updated directories of Voice Coil and Magnet Vendors and Distributors.

Voice Coil July 2021 is now available and full of valuable articles. Starting with Mike Klasco's insights on glue joints and attachment techniques used in speaker design. Followed by an updated and comprehensive directory of manufacturers and suppliers of adhesives, coatings, and treatments for the speaker industry. James Croft reviews the recent Bidirectional Speaker patent awarded to Resonado Labs, and Vance Dickason places the totally unique Purifi PTT6.5X04-NFA-01 midbass driver on Test Bench, followed by Beyma's 12LEX1300Nd 12” woofer with its unique Maltcross cooling system. Now available in print and online!

audioXpress' Technical Editor Jan Didden met with Bruno Putzeys and Lars Risbo, the founders of Purifi Audio, the new Danish company that the entire audio industry is talking about. The Netherlands Audio Engineering Society (AES) section invited the duo for a technical update on their plans, and they gracefully agreed to a presentation on June 13 at the Royal Conservatory of Music in The Hague, which Didden attended and reports here. This article was originally published in audioXpress, September 2019.