R&D Stories: A DSP Audio Processor at the Heart

This article, written by Al Clark (CEO, Danville Signal Processing), tells the story of his company’s R&D journey into the development of the dspNexus DSP Audio Processor. An interesting perspective about how the author’s experience led him to maximize the possibilities of digital audio, resulting in successfully bringing to market a dedicated DSP audio processor that could be used as a control center, a preamplifier, and a DSP engine for powered loudspeaker applications. This article was originally published in audioXpress, November 2021.

Stuart Yaniger shares his impressions and measurements of the Phonitor One d Headphone Amplifier System, designed by SPL of Germany. This product uses the company’s unique 120V circuitry, and also features an acclaimed AKM premium USB DAC and balanced stereo line output, effectively enabling it to function as a combination DAC and preamp. An interesting design also because of its Phonitor Matrix, a unique feature designed to electronically create a crosstalk signal and generate something similar to the effect of acoustic crosstalk around our head when listening through headphones. This article was originally published in audioXpress, November 2021.

This Test Bench article characterizes Eighteen Sound’s AMT200P Air Motion Transformer and accompanying XMT200 6.5” waveguide. This driver is the brand's latest entry into the high-frequency transducer category, specifically designed for the pro sound community. The Eighteen Sound AMT200P includes a rectangular throat with a Kapton diaphragm with a neodymium magnet structure, and is rated for a power handling of 90W AES above 1.2kHz, with a sensitivity of 105dB, and a recommended crossover frequency of 1.2kHz at 48dB/octave. While the AMT200P can be used as a standard planar device it can be also coupled with a dedicated constant directivity horn, the 90°x 20° XMT200, featured in the characterization.

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.

In Part 1 of this three-part article about circuit topologies that are used to provide specific functions for an amplifier design, the author discussed cascodes and folded cascodes. In this Part 2, he focuses on current mirrors and line stages. As the author writes, “As designers, we have many devices to choose from. Some devices are ideally suited to certain tasks. Other tasks require performance that is difficult to achieve. While many excellent devices exist today, ideal devices do not exist, except maybe in Spice simulations.” This article was originally published in audioXpress, October 2021.

This edition celebrates 35 years of Voice Coil, the Periodical for the Loudspeaker Industry. We discuss a new earphone technology for Balanced Frequency Range, Mike Klasco writes about Subwoofers and Bass, and James Croft reviews a new loudspeaker patent from Tymphany. Finally, Vance Dickason places Purifi Audio’s PTT4.0X04-NFA-01 Home Audio Midbass, and Eighteen Sound’s AMT200P AMT driver and XMT200 waveguide on the Test Bench. Now available in print or download.

The November 2021 edition of audioXpress looks at the latest industry trends in digital signal processing, and enabling fully adaptive audio DSP experiences. Roger Shively (JJR Acoustics) writes about how the unique acoustic space of the car interior can be defined by the use of DSP, and Al Clark (CEO, Danville Signal Processing) shares his company’s journey into the development of the dspNexus DSP Audio Processor. Now available for viewing online, download and in print.