Test Bench: The U80W Air Motion Transformer from Mundorf

As a respected manufacturer of high-quality condensers and crossover components, Mundorf is also capitalizing on the industry's “renaissance” in AMTs and now offers five models in this updated U series, each driver having the same width, but different heights. The U80W AMT model features a 63mm x 19mm pleated proprietary AMT diaphragm, an optimized rear chamber, a flat face plate with an optional secondary aluminum face plate, and is rated for 80W power handling and 94dB sensitivity. The U Series is the fourth in Mundorf's AMT portfolio. This article was originally published in Voice Coil, March 2022.

The Satori MW19TX-8 TPCD cone 7.5" woofer is the fourth TPCD diaphragm transducer to be explicated in Test Bench, the first being an Eminence compression driver and the remaining all woofers from SB Acoustics. The high-end MW19TX-8 has a substantial feature set with similar features as the rest of Satori series with TPCD cones, impressing immediately by its distinctive cosmetics and subjective performance, which this characterization illustrates.

Another great issue of Voice Coil magazine. Vance Dickason writes about the Multi-Tone Measurement Module (MTON) available for the Klippel KA3 Analyzer. Mike Klasco and Nora Wong (Menlo Scientific) compiled an updated Directory of Headphone Test & Measurement Equipment for 2022. We revisit a 2004 patent of a speaker using an "Internal Negative Stiffness Mechanism." And in Test Bench, Vance Dickason characterizes the latest Celestion CDX1-1412 1" Compression Driver and a new 3" dome midrange from Tang Band Speaker (TB Speaker).

An overview of Loudsoft's latest FINE Suspension Nonlinear FEA Spider and Surround Design software. This new transducer engineering tool, specific to the development of speaker surrounds and spiders (dampers), allows for the simulation of different types of surrounds and spiders from imported DFX files or created from templates with parameters selected by the user, and then outputs the compliance curves similar to the Kms and Cms curves measured by Klippel DA2 or KA3 analyzers.

Part of a new series of drivers announced in October 2020 by Wavecor, this woofer could also be advantageous in high-powered studio monitors. This high-power design targets home audio and home theater applications, including two-way (with larger ribbon/AMT drivers, or compression driver/horn combinations) and three-way speakers. This article was originally published in Voice Coil, January 2022.

The driver on this Test Bench is from B&C Speakers and clearly designed for professional audio. The 10NW76 was designed for uses in line arrays, small two-way monitors, and as a subwoofer, or as a midbass driver in multiway systems. It uses a proprietary 12-spoke (six double spokes) cast-aluminum frame with a series of cooling vents that allow air to move past the voice coil and across the front side of the neodymium motor assembly. The cone assembly consists of a curvilinear waterproof coated paper cone and dust cap. This article was originally published in Voice Coil, December 2021.

The March 2022 issue of Voice Coil offers a complete overview of loudspeaker cabinet design options, plastic enclosure materials, and production techniques, as well as an updated directory of Speaker Enclosure Vendors. This month, in Test Bench, Vance Dickason characterizes the Mundorf U80W from its latest U Series of Air Motion Transformers. And addressing demanding professional audio applications, this issue also includes a Test Bench on Eighteen Sound’s NSD1095N Compression Driver and XT120 Horn. Start reading online. Printed copies are on the way.

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.

While Voice Coil Test Bench reviews only make use of the Large Signal Identification (LSI) data from the Klippel analyzer, the reality is that there is an amazing list of 30 modules available for the KA3 that are seriously valuable for transducer and system development. As space permits, I will be covering a number of these modules in future issue of Voice Coil. The first module in this series is the Time Frequency Analysis (TFA) module. This article was originally published in Voice Coil, October 2021