Dynamo 400 is the smallest of MartinLogan's Dynamo powered subwoofers: a 20.3 cm woofer in a reflex cabinet, driven by a 75 W amplifier, to add low-end reach to a stereo or home cinema system.
Dynamo 400: woofer, reflex port and amplifier
The driver uses a polypropylene cone, a pressed-steel basket and a surround fitted the other way round from usual, facing inwards. That leaves more room for cone travel behind the grille and cuts air turbulence. The magnet assembly is sized for long strokes, while the light, well-damped cone adds no resonances of its own. The cabinet is tuned by a long port shaped to keep air noise down: the stated response runs from 30 to 200 Hz within ±3 dB, measured anechoically through the LFE input.
Amplification is Class D, fed by a switch-mode supply: 75 W continuous and 150 W peak, with modest consumption (20 W in typical use, 0.5 W in standby). Ahead of it sits the IME filter, an equalisation curve worked out from the inverse of the driver's natural response, which MartinLogan uses instead of simpler second-order filters to obtain even bass.
The rear panel carries two RCA sockets, left and right, the right one doubling as the LFE input for an AV receiver, plus high-level inputs on banana sockets for connection to the speaker terminals of a stereo amplifier. There are four controls: level, a low-pass filter adjustable between 35 and 120 Hz with a bypass position, phase at 0° or 180°, and permanent or automatic power-on. The cabinet stands on rubber feet and weighs 12.9 kg.
Specifications
- Type: powered reflex subwoofer
- Frequency response: 30-200 Hz ±3 dB (anechoic, LFE input)
- Woofer: 20.3 cm, polypropylene cone, inverted surround
- Amplifier: Class D, 75 W continuous (150 W peak)
- Line inputs: RCA left and right/LFE
- High-level inputs: left and right on banana sockets
- Input impedance: 8,300 ohms (RCA), 2,000 ohms (high level)
- Low-pass: 35-120 Hz, defeatable
- Phase: 0° or 180°
- Power-on: always on or automatic
- Consumption: 20 W typical, 90 W maximum, 0.5 W standby
- Feet: rubber
- Dimensions: 38.5 x 33.7 x 34.8 cm
- Weight: 12.9 kg
