SPT30A are compact, high intelligibility, reentrant type loudspeakers, designed for one-way or two-way sound and communication systems. Their sturdy, weatherproof, all metal construction is ideal for indoor and outdoor use in industrial plants, warehouses, schools, construction sites, transportation terminals, and recreational areas. Screw terminals make installation fast and easy. The Model SPT30A has a built-in, variable impedance selector switch for matching the speaker power requirements to a 25V or 70V constant-voltage line. The model SP308A has an 8-ohm impedance only. Engineered to simplify installation (with a uniquely designed all-purpose mounting bracket) and field maintenance (with a self-aligning, field replaceable diaphragm), use of Bogen horn-type loudspeakers saves both time and money. Speaker and mounting bracket are handsomely finished in textured mocha enamel. Diameter is 11-inch with a depth of 10-1/2-inch. A beam clamp is also available (BC1), as an option.