A passive outdoor subwoofer with a 254 mm woofer, designed to be buried in the garden or hidden beneath decking, so that the only part left above the soil is the outlet of its reflex port.
Dynamo Outdoor Sub 100: what sits below ground
The Dynamo Outdoor Sub 100 is meant to vanish into the garden. Its cylindrical body goes into the ground, or under the boards of a timber terrace, and all that shows at the surface is the end of the port, a mushroom-shaped cap roughly fifteen centimetres tall. Sound leaves through it and the driver breathes through it too: the same flared duct moves fresh air around the woofer, which is engineered to run cool, while keeping rain and standing water out. The flare also prevents port noise at large excursions.
The shell is made of high-density polyethylene, the plastic used for buried water mains, chosen because it lasts for years in contact with soil. MartinLogan reports that it passed trials fully submerged and at temperatures ranging from about -29 to 85 °C. Inside is a 254 mm woofer with a cone of mineral-loaded polypropylene, driven by a high-intensity magnet and a 50 mm four-layer coil wound on a glass-fibre former, sized to cope with high power.
This is a passive subwoofer: there is no amplifier on board, and it connects with ordinary speaker cable to an external power amplifier of 20 to 800 W. Response runs from 33 to 135 Hz within ±3 dB, so its job is to add weight to the low end of the Outdoor Living satellites, forming a system that can grow over time as further units are added. For the Crown CDi 1000 power amplifier MartinLogan supplies presets already tuned to these speakers.
Specifications
- Type: passive outdoor subwoofer for burial, reflex loaded
- Frequency range: 33-135 Hz ±3 dB
- Suggested amplifier: 20 to 800 W
- Sensitivity: 88 dB in room, 82 dB anechoic
- Nominal impedance: 8 ohms, suits amplifiers rated for 4, 6 or 8 ohms
- Woofer: 254 mm, mineral-loaded polypropylene cone
- Voice coil: 50 mm, four layers on a glass-fibre former
- Input: speaker cable
- Enclosure: high-density polyethylene
- Body only: 249 x 400 x 400 mm
- Port cap: 156 x 261 x 261 mm
- Overall with pipe and cap: 600 x 400 x 457 mm
- Weight: 21.8 kg
