The NSMT Model 20M Armada System

Shown: walnut

"...It has the speed and details of a big electrostatic panel, with more accurate sized images, but with "big balls" bass and dynamics."
Terry London, Stereo Times

System Price: $8,995

 

Since its introduction in the 1990s, the 20M Armada System has been a combination of a pair of our 20M acoustic suspension, coincident point source monitors, two of our 15EXP active bandpass subwoofers, and a pair of our custom sand-fill-able Sandbags speaker stands. The new 20M Armada System is a combination of a pair of the new 20M monitors and two of our new Bass Foundation subwoofers.

The previous 20M and 20M Armada System have been lauded for their stellar performance. In his 2001 review of the 20M, Doug Schnider of Soundstage magazine said he was mesmerized by the precision and startling resolution with which the 20M rendered instruments and that it imaged at least on par or better than the best imaging speakers that he had heard.

Later on Russell Lichter of Stereo Times was so impressed by the 20M Armada System that he bought it for his reference.

And Kurt Lundvall of Lundvall Mastering described the 20M Armada System as simply allowing him to get closer to creating a perfectly balanced master than he ever thought possible.

The 20M Coincident, Point Source, Acoustic Suspension Monitor

The ideal speaker would be a full range single driver speaker. But although the sound of a single driver speaker can be intoxicating it has limitations in its high frequency and low frequency reproduction. The 20M uses a single, full range coincident, point source driver array as the solution to the problems of the full range single driver speaker.

The single, coincident, point source driver array used in the 20M has a tweeter located in the throat of the woofer where the driver's dust cap usually is to address the high frequency inadequacies of the full range speakers. This placement ensures that the woofer and tweeter have identical acoustic centers and identical directivities at the crossover frequency. High and low frequencies emanate from the same place. Because we use a minimum phase first order crossover that preserves phase coherence, the 20M is also phase coherent. The high frequency response of the 20M is beyond 20,000 Hz and the low frequency response is down to 30 Hz.

However, driven extremely loud coincident source driver array speakers also have limitations in that extreme cone motion can produce Doppler effects that can affect the sound.

There is a way in which loudness and perceived bass performance are interrelated and it is through psycho-acoustics. Simply put, there are two aspects to bass: bass that we hear and bass that feel. Most speakers can produce reasonable bass amplitude (bass that we hear) but are woefully lacking in the ability to pressurize the air in the room – the bass that we feel. Most listeners increase the loudness of their music systems to pressurize the air in the room. However, if the speaker can pressurize the air in the room, the listener is often satisfied listening at a lower volume.

Our solution to scaling up the sound of the coincident driver array speaker has been to add a pair of our full featured active 15EXP subwoofers that augment low bass performance and can filter out low bass that produces extreme cone motion in the coincident driver if there is a desire to play the speakers at disco levels. The new solution is the replacement of the 15EXP subwoofers and the Sandbag speaker stands with the new Bass Foundation pedestal subwoofer.

The Bass Foundation Active Bandpass Subwoofer

The design of our Bass Foundation subwoofer is inspired by the research, development and refinement of our 15EXP subwoofer which dates back to the 1990s and more recently the research and design of the subwoofer in our Model 100 speaker.

In his review of the 15EXP subwoofer in Enjoy the Music magazine, Dr. Jeff Rabin noted that, "... when it comes to integration, few subwoofers integrate as well as the 15EXP, and the ability of the 15EXP to play the "the lower registers” (that is to pressurize the room) was ..”downright menacing."

Francisco Duran of Positive Feedback magazine noted that the drum whacks produced by an earlier version of Model 100 were "... the deepest most powerful ... drum whacks ..” that he had ever heard."

In his review of the Model 100, Terry London noted the bass produced by he Model 100 in his “..vast listening space was somewhat shocking."

Others who have heard the Model 100 such as Barany commenting on Audiogon Forum have described the bass of the Model 100 as “otherworldly” and the best bass they have heard.

Most subwoofers work on the principle of bass replacement with the subwoofer producing the lowest bass frequencies and the main speakers or satellite speakers producing the frequencies above the subwoofer's. This approach is inspired by the need to play the speakers at very high volume and to allow the main and satellite speakers to handle power better.

The approach we prefer is to use the subwoofer to reinforce the bass performance of the 20M monitor. It is inspired by our understanding of psycho-acoustics and bass reproduction. That is because most of the desire to drive loudspeakers very loud is driven by a desire to pressurize the air in the room. Secondly, using crossovers to partition bass frequencies between the subwoofer and satellite speakers tends to create discontinues and phase irregularities in bass reproduction. For sure the Bass Foundation subwoofer is active and full featured and is outfitted with a 6 dB per octave high pass crossover to partition the 20M Armada system's bass response which may be necessary for playing the system at very high volume.

However, our bass reinforcement approach requires a subwoofer that has flat bass response over a wide range of bass frequencies and the best approach is to use a bandpass design.

The New 20M Armada System

Several features contribute to the stellar performance of the new 20M Armada system. The 20M's combination of time coherent, point source, first order, two-way, acoustic suspension design coupled with innovative cabinet and crossover designs and accurate voicing, make the Model 20M incredibly transparent and true to the source. The ability of the Bass Foundation subwoofer to seamlessly integrate with the 20M and its ability to produce accurate bass and pressurize the room results in a combination that is a transcendent high fidelity music system that is capable to 20 Hz to 20 kHz reproduction. The system offers great flexibility to fine tune its acoustic output, imaging, and soundstaging by easily towing the 20M monitor in and out on the horizontal axis and the ability to adjust the low bass output especially for asymmetrical rooms.

The reader is encouraged to read more about the 20M monitor here, the white paper on the design and response of our 15EXP subwoofer is here, and the white paper on our Mastering Series loudspeakers is here.

 

Special Features

Design: Two-way  time coherent, first order, coincident source, acoustic suspension monitor with active bandpass pedestal subwoofer

Drivers: Coincident source driver array with1 inch fabric dome tweeter and seven inch woven TPX cone woofer (monitor) with10 inch paper cone woofer in active pedestal subwoofer

Crossovers: single inductor to monitor woofer and single capacitor to the tweeter (monitor), active 24 dB per octave crossover to the subwoofer with optional provision for 6 dB high pass to satellite speakers

Wiring: Multi-strand copper to tweeter and woofer (monitor)

Connectors: Fully insulated, gold plated five-way binding posts

Connections for mnonitor to amplifier via provided multi-strand copper speaker cable.

 

Provisional System Technical Data

Dimensions: combined height 42 inches

Subwoofer - 12 inches wide by 12 inches deep; top panel 12 inches wide by 11 inches deep.
                    (front panel slopes two degrees from the bottom to the top)
 
Monitor - 9 inches wide by 9.5 inches deep; top panel 9 inches wide by 9 inches deep (without speaker grill)
               ( rear panel slopes two degrees from the bottom to the top)
 

Combined System Frequency Response: 20 Hz - 20 kHz

                                                                   27 Hz - 20 kHz   +/- 2.5 dBs

20M Monitor

Sensitivity: 87 dB 1 watt/m

Rated Impedance: 8 ohms

Minimum Impedance: 6.5 Ohms

Recommended Power: 5 - 200 watts

Shipping Weight monitor: 50 pounds per pair

Cabinet construction:

sealed anti-resonant medium density CARB 2 fiber board and natural plywoods.

The rear of the cabinet is slanted 2 degrees, from the bottom to eliminate standing waves in the cabinet.

 

Standard Finishes:

natural birch plywood, sapele plywood, and walnut plywood. Other finishes available at additional cost.

Warranty: 5-year limited warranty.

 

Bass Foundation Active Bandpass Subwoofer

250 Watt amplifier

10 inch long-throw treated paper cone woofer

Auto-on power switch controlled by input signal

Continuously variable crossover from 40 Hz to 180 Hz at 24 dB/octave

Volume control to adjust output

Overload and thermal and fuse protection with output relay

Gold plated RCA line level input and output connectors

Removable IEC type power cord

Discrete TO-3P output devices

THD: Less than 0.05%

S/N ratio: Greater than 85dB

Power requirements: Switchable, 120/240 VAC, 50/60 Hz

Shipping weight: 45 pounds each

Warranty: 5-year limited warranty.

The front of the cabinet is slanted 2 degrees, from the bottom to the top to improve phase alignment between the subwoofer and the partnering monitor and  to eliminate standing waves in the cabinet.

Standard Finishes: natural birch plywood, sapele plywood, and walnut plywood. Other finishes available at additional cost.