QSC Series Models AcousticCoverage Series (nb ) "no back can-no bounce" models are 4.5" and 8" full-range ceiling mount 4.5" and 8" full-range in-ceiling speakers. Each comes with a 70/100V transformer and are suitable for a wide variety of audio/video conferencing, public address audio/video conferencing, public address and ambient music. The AcousticCoverage series is designed to offer integrators a cost-effective solution a cost-effective solution for applications applications where voice reinforcement where voice reinforcement coverage is the primary objective, while providing enhanced musicality enhanced musicality not often seen in not often seen in Ambient Music products. Environmental.