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NSMT Armada System: 20M Monitors,
Sandbag Stands, 15EXP Subwoofers
 

 

July 2011

 




It was about time for me to go forth into the world, loins girded with the sword of subjective truth, and review a loudspeaker, so Clement suggested a company in North Carolina called NSMT that built reasonably priced speakers, including models using a rather special coincident, 2-way driver. I contacted owner/designer Erol Ricketts and arranged for review samples.

NSMT produce several different lines of loudspeakers, from classic 2-way monitors to transmission line towers to d'Appolito configurations. They've been in the loudspeaker business since 1990 and because they are a small, direct-sales company they can offer lower prices than the big names with their big advertising budgets. NSMT's top-of-the-line Mastering Series includes the speaker under review, the 20M.

In this review I will occasionally make reference to my first pair of small loudspeakers, KEF 101s. I liked these speakers a lot and had them for two decades, but they were inefficient, wouldn't play very loud and they lacked bass. They were built around the classic T27 tweeter and the Bextrene-coned B110 mid-woofer, both designed and manufactured by KEF. KEF were the first, and at the time perhaps the only, company using computers running Fast Fourier Transforms to produce closely matched pairs: 90Hz - 30kHz +/- 2dB at 2m on reference axis (-10dB at 47Hz and 40kHz). The result was exceptional imaging and legendary neutrality. It was inevitable I'd cast my mind back to Raymond Cooke's little masterpiece in reviewing the NSMT 20M. They have things in common.

Like my old KEFs, the NSMT 20Ms ship in matched pairs. As Erol Ricketts wrote, “Often times we get perfect matches, otherwise we match to within two percent. Sometimes in the past we had to dismantle the 20M drivers and swap tweeters to get perfect matches. Nowadays the tolerances coming from the factory are much, much better.” This level of component matching is extraordinary in any loudspeaker, but especially so at this price point. Moreover NSMT keeps a record on file for each pair of drivers they ship. So if a customer blows a tweeter—something which has happened only two or three times—the replacement driver will be perfectly matched.

The cabinet is an integral part of the acoustical behavior of any loudspeaker, critically so when the crossover is first order, as has the 20M. The cabinet is very solid, the workmanship first rate. Along with some well-known names, such as Wilson Audio, NSMT manufactures its cabinets in-house. The assures consistency and quality. To put this into a certain perspective, Wilson Audio's least expensive loudspeaker, the Duette, sells for almost $20,000 with stands. The 20Ms with stands cost around 20% of that.

20M Monitors. The 20M is an acoustic suspension design, 14” x 9” x 10”, constructed of internally braced ” MDF with red walnut veneer, weighing 25 pounds each. The rear of the speaker cabinet is sloped at 2 to minimize coloration by distributing the frequencies of any internal resonances and eliminating standing waves. (It is 9” deep at the top, 9.375” at the bottom.) The vertical edges of the cabinet are quarter-round inserts of Peruvian walnut that are somewhat darker than the veneer. The frame of the protective black cloth cover attaches to four, flush plastic inserts and is designed with a 1⁄8” air gap between the cover and the front baffle. I've never seen this ingenious feature before—like rounded corners, it helps to minimize diffraction. The 20M is magnetically shielded, bi-amp/wireable (four thick, solid copper jumpers are included), has a nominal impedance of 8 Ohms with a minimum impedance of 6.5 Ohms making it an easy amplifier load. Efficiency is 87dB and frequency response is 55-20,000Hz 3dB. The 20M is 6dB down at 47Hz and 10dB down at 38Hz (both referenced to 1kHz), fairly typical behavior for an acoustic suspension design. The “missing” lower octave-and-a-half accounts for the configuration dubbed the “Armada System”, consisting of a pair of monitors, a pair of custom speaker stands, and a pair of 15EXP (or 15EXP-SE) subwoofers.

On the rear of the cabinet are two pairs of insulated five-way binding posts. I was surprised to learn these are not your ubiquitous gold-plated brass posts that look good, work well, and sell for maybe $15 a pair. A high-end junkie would be pleased with these: they are made in Sweden by Supra Boxcon from solid copper, plated with 24 carat gold, and accept banana, spade and wire connections up to 7 gauge. And they retail for $60 a pair, an impressive and suggestive touch. The crossover uses a metal oxide resistor, a film foil capacitor and a perfect lay hexagonal wound inductor. Metal oxide resistors are carbon free and have low thermal and contact (1/f) noise and high thermal stability. Perfect lay inductors have no hysteresis or saturation distortion, low skin and proximity effect losses, low resistance and low self inductance. They are wound, tied, and dipped in enamel: there is no nylon bobbin to increase dielectric constant. Film foil capacitors have low intrinsic noise and excellent transparency. Even the wires connecting the drivers to the crossover are chosen for their sonic characteristics, stranded copper for the woofer, silver plated copper for the tweeter.

The Sandbag stands are well made and beautifully finished and come in 24”, 27”, 30” and 32” heights. They are constructed of MDF and painted in satin black (also available in walnut veneer for an additional charge). The central support of the 27” version is 6” square, offset 45 relative to the top and bottom plates and can be filled with sand to eliminate resonance and increase mass and stability. Thus the name “Sandbag Stands.” There are two round rubber pieces that seal the fill hole in top of the column to preclude leakage. The base plate takes four adjustable spikes (included). And there are also eight small squares of Plasti-Tak that firmly, and I mean firmly, adhere the speaker to the stands. The end result is attractive, massive and quite stable.

 




Subwoofer. The 15EXP has an internal 10” long-throw, doped paper cone driver, and an internal 200 watt “high headroom” class A/B amplifier that has thermal, overload and fuse protection. Considering the system's limited bandwidth, 200 watts represents quite a lot of power. (The 15EXP “Special Edition” costs more, uses a more powerful, external amplifier, and has a remote control for volume and crossover point.) Each 15EXP weighs 45 pounds. The cabinet design is unusual. It is constructed of ” formaldehyde-free MDF; top and bottom painted in satin black; front, back and sides veneered in black cloth. The driver is mounted horizontally on an internal shelf (which also braces the cabinet)—so the rear of the driver sees a sealed cavity. The front of the driver sees a tuned-port cavity and the front-firing port is 4.625” diameter to minimize “chuffing” at high sound pressures. The upper—acoustic suspension—half of this design provides better transient response than any ported cabinet; while the lower—ported—half of the design provides a passive 12 dB/octave band pass filter. Unlike most designs, the 15EXP is not dependent on digital signal processing and will perform very well without it. The illustration shows it's response curve without any electronic processing—it is flat within a few decibels within its pass band. This is remarkable performance.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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