Test Bench: The PTT6.5M08-NFA-01 6.5" Midrange from Purifi Audio

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.

The September edition of audioXpress is our always popular Speaker Builder - Speaker Focus edition. Once again, audioXpress focuses on loudspeaker building, design, and testing and for this issue we have combined two great DIY articles with a review of the PureAudioProject Trio15 Heil AMT speaker system. Ward Maas reports from the High End 2019 show in Munich, Jan Didden met with Purifi Audio's Bruno Putzeys and Lars Risbo and comments on the company's research, and much more.

A new Danish audio company, founded by Bruno Putzeys, Lars Risbo, and Peter Lyngdorf was recently announced. The name is Purifi Audio, and as you can guess from the founders involved, the venture promises Class D amplifiers with record-breaking performance "unmatched by amplifiers of any operating class." But the new company will be doing more than amplifiers, since it also revealed a new 6.5" woofer with "magnitudes lower intermodulation distortion across frequency and SPL."

A new Danish company, founded by Bruno Putzeys, Lars Risbo, and Peter Lyngdorf will be making its first public presentation to the industry in Munich 9-12 May, concurrently with High End 2019. The name is Purifi Audio, and as you can guess from the founders involved, the venture promises Class D amplifiers with record-breaking performance "unmatched by amplifiers of any operating class." But the new company will be doing more than amplifiers, since it will also reveal a new 6.5" woofer with "magnitudes lower intermodulation distortion across frequency and SPL."