Near Field Studio Grade Subwoofers
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ServoBass® specializes in crafting cutting-edge audio solutions for professionals. Our servo-controlled subwoofers redefine studio sound, offering unmatched clarity and precise stereo imaging. Designed to deliver the essential bottom octave in a compact, desktop-friendly form that minimizes room reflection effects, our subwoofers seamlessly complement any near-field monitors by enhancing the critical 30–60 Hz range with exceptional clarity, low distortion, and precise stereo imaging.
Experience the difference with ServoBass®.
Enhancing Woofer Performance with MFB and Crossover Optimization
Speaker acoustics theory states that voice coil acceleration is directly proportional to the acoustic output of a woofer in a sealed enclosure when operating in piston mode below the breakup frequency.
In the first chart, the green plot represents voice coil acceleration without MFB, while the red plot shows the improved response with MFB activated.
Additionally, close microphone measurements on the driver’s acoustic axis are known to closely approximate free-field measurements. In the second chart, the red plot shows the microphone output with a 100 Hz crossover filter, the blue plot with a 200 Hz crossover filter, and the green plot with the subwoofer’s full bandwidth.
Design Considerations
Most small near-field monitors lack bass reproduction in the 30–60 Hz range to avoid bass-midrange intermodulation, which degrades clarity and imaging. While common subwoofers use ported enclosures to enhance bass, they often result in overhanging, sustained, “boxy” bass transients.
ServoBass’s compact 8x8x8-inch near-field subwoofers address these issues with a relatively high crossover frequency of 100 or 200 Hz. Designed for desktop use with monitors placed on top, they ensure perfect wavefront alignment at ear level.
Using 4th-order Linkwitz-Riley crossovers, these subwoofers integrate seamlessly with near-field monitors, ensuring smooth phase transitions at the crossover frequency for a flat response. Motion Feedback (MFB) technology delivers tightly controlled bass transients, eliminating the drawbacks of resonant ported designs.
Frequency response
Green plot - with MFB disabled
Red plot - with MFB enabled
Cross Over response
ZRS-1 Crossover Response (Close microphone test) 100 Hz
ZRS-1 Crossover Response (Close microphone test) 200 Hz
ZRS-1 Crossover Response (Close microphone test)
Green - 100 Hz Blue - 200 Red - Wideband
Inside our ZRS-1 Subwoofers
The ZRS-1 Plate Amplifier combines an MFB control circuit, a high-power Class D amplifier, and a robust switching power supply. MFB enables a flat frequency response with real-time voice coil dynamics control, while real-time temperature monitoring prevents overheating damage.
Key Features:
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Subwoofer volume control
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Selectable 100 Hz and 200 Hz crossover options
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Full-range 30–400 Hz response for user-defined crossover
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Bypass mode routes the input signal directly to monitors while muting the subwoofer
The ZRS-1 features a 6.5" driver with a custom-designed sensor mounted on its voice coil former, housed in an 8x8x8-inch enclosure designed to fit under most near-field monitors.
ZRS-1 Block diagram
THD & 3rd Harmonics Reduction by MFB
Additional Reading
The linked articles explore the history of passive and active bass enhancement methods and the design of the ZRS-1 desktop subwoofer. Measuring 8x8x8-inch, the ZRS-1 complements small studio monitors by delivering powerful, tightly controlled bass in the 30–60 Hz range using Motion Feedback dynamic control of the woofer's voice coil.
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About Our Subwoofers in the Sound on Sound newsletter
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Read about our subwoofers in an article featured in AudioXpress​
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About our CEO Zami Schwartzman in AudioXpress​
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Motion Feedback Desktop Subwoofers in AudioXpress
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