Surface mount compression driver loudspeaker, through proven performance, patented VT/VTF Series have earned worldwide acclaim for service reliability. These cost-effective units offer compact size, functional flexibility, optimum intelligibility, effective sound distribution, and high-level output. All models contain a high efficiency compression driver with maximum acoustic conversion efficiency. (A quality which reduces number of units needed to attain specified sound pressure levels and provides substantial savings in amplification-power requirements and labor costs.) Die-cast, water-sealed construction withstands vandalism, vermin, moisture, corrosion, and vibration during indoor or outdoor use. Selection includes a basic 8-ohm version and 70.7 or 25-volt transformer models with DC blocking capacitor (C) where noted. All models terminate via barrier strips. VT Series models are surface-mount units; VTF Series are flush-mount units for recessed installation. VT Series mounts standard 4" E.O. Boxes; VTF Series mount 4" or 4 11/16" SQ back boxes and require model AR or MR adapter rings respectively (order separately) Optional mounting accessories are offered including indoor and outdoor enclosures, a bi-directional housing, adapter plates and rings.