The subwoofer shall be a high-power, direct-radiating design suitable for suspension or ground placement.  The transducer shall be a heavy-duty 18” (460 mm) driver with die-cast frame, vented pole piece, and a 4” (100 mm) edgewound copper-clad aluminum ribbon voice-coil.  The enclosure shall be vented with a tuned port.  The subwoofer input connectors shall include one M5 screw terminal connection and two Neutrik NL4 type sockets, wired in parallel for pass-through to additional speakers.

The subwoofer shall meet the following performance criteria.  Power handling: 240 watts continuous pink noise (24 continuous hours, 40 Hz to 1 kHz), 720 watts continuous program.  Frequency response (10 dB below rated pressure sensitivity, with recommended equalization):  40 Hz to 400 Hz.  Pressure sensitivity (1 watt at 1 m, 50 Hz - 150 Hz avg.): 95 dB free field.  Impedance: 8 ohms nominal. 

The subwoofer enclosure shall be made of plywood and finished with black urethane paint.  The subwoofer grille shall be made from a single punched steel plate and finished with black acrylic paint.  The dimensions (W x H x D) shall be 29.13” x 22.56” x 27.48” (740 mm x 573 mm x 698 mm) and weight (including accessory brackets) shall be 145.5 lbs. (66 kg).  The subwoofer enclosure shall be equipped with M10 threaded steel plates for the secure attachment of optional accessory brackets.  Available accessory brackets for suspension and stand mounting shall be made of steel.

The subwoofer shall be TOA model SR-A18B.
The rigging frame shall be TOA model SR-RF12.
The tilt joint plate shall be TOA model SR-TP12.