The compact enclosure is constructed from premium 18mm (3/4”) multi-laminate Birch plywood, and houses a single 4.5” voice coil, 18” (457mm) neodymium LF drive unit. The enclosure includes a single M20 threaded polemount adapter, allowing the mounting of EMS Series fullrange loudspeakers above. Also as standard, the S-18 is supplied with castors for the rear and is fitted with rubber feet underneath and matching recesses on top to allow stable stacking of multiple enclosures. Two Neutrik® speakON™ NL4 connectors are provided for input and enclosure link, and a pair of steel bar handles allow easy lifting. Lastly, a tough hex-punched steel grille protects the drive unit from damage whilst in use or in transit. The enclosure is finished in a rugged black  textured polyurethane or white textured paint as standard, though RAL colour matching and weather-protected outdoor options are available.

The S-18 requires an active crossover to function correctly – although the choice of filter points is very wide, allowing the user to tailor the response to exactly what is required. Cardioid DSP program settings are also available to create arrays with significant rejection to the rear of the subwoofers, by stacking three enclosures in a block (two facing forwards, one facing backwards).

The S-18 can add low frequency power and extension to systems based around any EM Acoustics fullrange product, or for fullrange products from other manufacturers. The S-18 requires active high/low pass filters and a single amplifier channel capable of delivering 1500-2000W RMS into a 4 ohm load. For optimal results, the DQ Series Advanced System Amplifiers should be used.