AD-C820 and AD-C821 are acoustically identical and designed for music playback, public address and distributed audio in applications that require high output from ceiling mounted loudspeaker. The AcousticDesign series of installation loudspeakers has been designed for trouble free operation and versatility. Both models use custom designed transducers and crossover networks, in combination with an acoustically optimized enclosure (AD-C800BB), or as fully integrated, sealed system (AD-C821). These loudspeakers continue AD series philosophy of bringing natural and accurate sound quality combined with versatility and reliability to high-ceiling applications. AD-C820 assembly includes coentrant transducers, 70/100V transformer and crossover mounted on an ABS baffle. 8-inch woofer is equipped with treated paper cone on steel frame. In optimized enclosure the usable low frequency of the system extends to 52Hz. 1.4-inch compression driver fires through the center of the woofer and is acoustically mated to woofer for smooth transition at crossover. The system achieves 90° axisymmetric coverage. High-current, low tolerance network components provides smooth full-range, passive performance. The included 70/100V, custom designed transformer is optimized for low line loss as well as accurate and transparent acoustic performance. AD-C820/C821 loudspeakers measure 91dB sensitivity (1W/1m) and at full continuous power are capable of producing 114dB SPL (1W/1m) output.