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Sub Duo

NSMT Sub Duo subwoofer

The Bass Foundation Subwoofer Duo
Frequency response: Variable 22 - 145 Hz
Dimensions: 12 X 36 X 15 inches (W X H X D)

Price: $4,495


The Bass Foundation Subwoofer Duo (Sub Duo) is our new flagship subwoofer. It is a bandpass design. The same design used in our Model 100 loudspeaker and in our Bass Foundation and 15EXP subwoofers.

Like all of our subwoofers, the Sub Duo produces deep, accurate, bass with excellent transient response and exceptional subsonic energy that can load and surprisingly pressurize listening areas.

Our design goal was to build a very powerful, elegant, compact, articulate subwoofer that can easily integrate with any loudspeaker – from a micro monitor to the largest floor stander.

To accomplish this we relied on our experience designing highly regarded bandpass subwoofers – experience that dates back to the 1990s when we introduced the 15EXP, our first bandpass subwoofer – and the much heralded recent design of our Bass Foundation Subwoofer. The Sub Duo uses two of the woofers used in the Bass Foundation Subwoofer and the same amplifier.

Our bandpass subwoofers integrate seamlessly because bandpass subwoofers produce faster transient response and flatter bass response over a wider frequency range than other designs.

In a bandpass subwoofer, the woofer's back is mounted in an acoustic suspension sub closure that produces quick, accurate, transient response. The front of the woofer outputs into a vented sub enclosure. The combination of acoustic suspension and tuned vented bass enclosures produces powerful, flat, extended, bass response.

Bandpass subwoofers are challenging to design because the designer has to consider the design of the acoustic suspension rear enclosure, the design of the vented front enclosure, and the size and tuning of the port. As the name bandpass suggests, the cabinet acts as a low pass filter that shapes the bandwidth of frequencies that it outputs. The designer manipulates that bandwidth by shifting values for the rear enclosure, the front enclosure, and the port to achieve the desired frequency response.

A well-designed bandpass subwoofer has better transient response, flatter frequency response, and greater bass extension than alternative designs of similar size -- characteristics that allow easy integration with loudspeakers. Moreover, as in a transmission line design, in a bandpass design, the woofer can generate high dynamic levels without distortion because cone motion is controlled and reduced by air pressure on both sides of the woofer cone.

While the frequency response of most active subwoofers tends to be dependent on elaborate artificial shaping of the response by electronic means, bandpass subwoofers achieve exemplary, transient response and extended, linear bass response primarily through the natural and harmonious acoustic mating of its woofer and its bandpass cabinet.

The ability of our bandpass subwoofers to play powerful articulate bass and to easily integrate with any sized loudspeaker has been lauded in several magazine reviews:

In his review of our 15EXP bandpass subwoofer, 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 noted that the drum whacks produced by the Model 100 bandpass subwoofer were "... the deepest most powerful ... drum whacks ..” that he had ever heard." (

Terry London noted the bass produced by the Model 100 bandpass subwoofer in his “..vast listening space was somewhat shocking." (

Barany described the bass of the Model 100 as “otherworldly” and the best bass he has heard. (Audiogon Forum)

The Sub Duo transcends the performance of other subwoofers by incorporating two bandpass chambers each driven by a 10 inch woofer. The woofers are powered by a modified full-featured 250 watt, class AB amplifier. Think of the Sub Duo as a design that essentially incorporates two of the highly regarded Bass Foundation Subwoofers in a single cabinet.

As a result, the Sub Duo has incredible capacity to load (pressurize) any listening space. The Sub Duo produces the kind of high impact, accurate, articulate, extended bass with a level of refinement and excitement that few subwoofers can match and it integrates easily with any loudspeaker.

However, the Sub Duo is not only one of the best high performing subwoofers, it is also fine furniture. The cabinet features soft rounded edges with satin black painted top, front, and bottom panels, and black fabric covered sides and back panels. Because of its unique design, the woofers cannot be seen. The Sub Duo takes up only 12 by 15 inches of floor space. It is an elegant-looking package that can sit out in any room.



Active double vented bandpass cabinet design that is ideal for music and home theater systems

Two 10 inch long-throw paper cone woofers in separate bandpass sub enclosures

Modified 250 Watts RMS class AB amplifier

Health friendly/Eco-friendly cabinet and paint

Front ports allow near wall placement

Auto-on power switch controlled by input signal

Volume, phase and crossover controls to adjust output

Continuously variable crossover

Gold plated RCA line level input and output connectors

Removable IEC type power cord

Output protection circuit with relay

Discrete TO-3P output devices

Thermal, overload and fuse protection

Line level and speaker level inputs Line level and speaker level outputs

Cabinet construction: CARB 2, Cross-braced MDF

Standard Finishes: satin black. Other finishes available at additional cost.

Warranty: 5-year limited warranty.



Frequency Response: Variable 22 Hz to 145 Hz.

Dimensions: 12 X 36 X 15 inches (W X H X D)

Input Connectors: Left and right line level RCA connectors, left and right speaker level binding posts

180 degrees phase switch

Continuously variable crossover from 40 Hz to 180 Hz at 24 dB/octave with 24 dB/octave roll off pattern

250 watts RMS modified class AB amplifier

THD: Less than 0.05%

S/N ratio: Greater than 85dB

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

Shipping weight: 85 pounds each