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MartinLogan Dynamo™ 400

Powered subwoofer

Item # 839DY400B

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Our take on the MartinLogan Dynamo™ 400

A healthy dose of MartinLogan bass

MartinLogan's Dynamo 400 features a high-excursion 8" woofer driven by a highly efficient built-in Class D amplifier. This is the entry-level sub in MartinLogan's 2018 Dynamo lineup, but it still delivers punchy bass down to 30 Hz — that's deep enough to lend serious kick to movie and TV show special effects.

Product Highlights:

  • frequency response: 30-200 Hz (±3dB)
  • built-in amplifier delivers 75 watts of continuous power (150 watts peak)
  • 8" high-excursion polypropylene woofer with an inverted surround
  • bass-reflex (ported) cabinet with down-firing woofer and slot port
  • continuously variable low-pass 35-120 Hz crossover (back panel)
  • level control (back panel)
  • auto on/off switch (back panel)
  • phase switch (back panel)
  • RCA stereo/LFE line-level input
  • speaker-level inputs
  • satin black finish
  • 13-5/16"W x 15-1/4"H x 13-3/4"D
  • weight: 28.5 lbs.
  • warranty: 3 years (with product registration)
  • Our 60-day money-back guarantee

What's in the Box:

  • Powered subwoofer
  • 6.5' AC power cord
  • User's Manual

Hands-on research

Features and Specs

Enclosure Bass reflex
Video Shielded No
Woofer Size (inches) 8
Woofer Composition Polypropylene
Firing Direction Down
Wireless No
Preamp-Level Inputs Yes
Speaker-Level Inputs Yes
Speaker-Level Outputs No
Low-Pass Crossover Freq 35-120
High-Pass Crossover Freq N/A
Phase Switch Yes
Amplifier Output (watts) 75
Frequency Response 30-200 Hz
Height (inches) 15-1/8
Width (inches) 13-5/16
Depth (inches) 15-1/4
Weight 28.5 lbs
Speaker Parts Warranty 3 Yrs w/ Registration
Speaker Labor Warranty 3 Yrs w/ Registration
Amplifier Parts Warranty 3 Yrs w/ Registration
Amplifier Labor Warranty 3 Yrs w/ Registration

Product Research


Powerful, High-Excursion Woofer: The MartinLogan Dynamo 400 powered subwoofer features and advanced-design 8" polypropylene cone woofer that is down-firing with an inverted rubber surround and stamped steel basket, along with a powerful magnet, motor, and suspension design. This advanced-technology woofer pairs a high-power magnet structure with a low-mass diaphragm to provide massive excursion while perfectly preserving the tiniest bass detail. The exceptional damping properties of the cone ensure a smooth, non-resonant response necessary for truly seamless blending with high-performance loudspeakers. Every element of Dynamo 400 powered subwoofer has been meticulously designed to deliver an outstanding low-frequency performance without a hint of distortion.

Class D Amplifier Technology: The Dynamo 400 powered subwoofer's class-D amplifier is rated at 75 watts (RMS)/150 watts (Peak), operates with extremely low levels of distortion, and delivers dynamic impact with plenty of overhead. Low- noise, high-power switching power supplies produce clean power efficiently in a small space and effortlessly provide tremendous levels of current. Both feature high-quality MOSFET transistors, transformers, noise-suppression networks, and control circuitry. The switching power supply combined with reliable class-D technology means there's virtually no energy lost in the subwoofer system.

High-Density Cabinet Construction: The powered subwoofer's cabinet is constructed from the finest composite material for acoustical integrity and is finished with an attractive vinyl coating. Four robust rubber feet isolate the subwoofer cabinet from the floor to prevent any unwanted vibration, coloration, and distortion.

Low-Turbulence Port Design: When properly optimized and executed, ports are a convenient, cost-effective way to increase low-frequency output. The Dynamo 400 features a tuned, long, low-turbulence, down-firing port designed to provide superb low-end extension while minimizing port induced distortion.

Inverse Mathematical Equalization (IME) Filter: The IME filter used in the Dynamo series powered subwoofers is derived from the inverse of the unfiltered driver response. Precision IME filtering yields extremely accurate low-frequency response; superior to that provided by the simple second-order high-Q filters typically found in subwoofers in this price range.

Variable Controls: The Dynamo 400's precision low-pass filter can be set between 35Hz and 120Hz to seamlessly blend with your loudspeakers (there is a "Bypass" setting if you are using the sub's Right line-level input as an LFE input). The powered subwoofer's phase control can be set to 0° or 180° to match the phase of your loudspeakers. The powered sub's level control (min-max) can be dialed in to match the output level of your loudspeakers.

Line-Level & Speaker-Level Inputs: The Dynamo 400 powered subwoofer features left and right inputs via RCA line-level, as well as speaker-level connections in the way of banana plugs. The Dynamo 400's right line-level RCA input doubles as an LFE input for home theater applications (make sure to set the sub's crossover to "Bypass" when utilizing the LFE input).

Note: The powered sub's speaker-level inputs consist of banana plugs for use with single banana connectors only. The speaker level inputs will not support bare wire connection and do not support dual banana connectors.

Auto Power On/Off: The powered subwoofer will automatically enter a power saving mode when no audio signal is detected. The subwoofer will automatically come out of power saving mode when an audio signal is detected. You can also manually turn the subwoofer On.

Our Product Research Team

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Q & A

Customer Q&A


Looking for more? Check out the next model in this lineup.

MartinLogan Dynamo 600X

Better bass and convenient wireless setup and control options

The MartinLogan Dynamo™ 600X offers these features:

a larger 10" woofer

a more powerful 120-watt amp

better low-frequency extension, down to 27 Hz

wireless control via a free MartinLogan Bluetooth® app

automatic room correction via a free ARC Mobile app

compatibility with optional MartinLogan add-on wireless kit, for cord-free connections