The Yamaha RX-V381BL fits well in just about any listening environment from spacious living rooms to small apartment spaces and basements. This wallet-friendly 5.1-channel receiver is ready for the latest 4K Ultra HD content, including 4K Blu-Ray discs encoded with HDR (High Dynamic Range) information. Specialized DSP modes let you get the best sound from any kind of setup, whether you connect a single pair of bookshelf speakers or a full five-channel speaker system. Built-in Bluetooth lets you stream from compatible mobile devices for nearly boundless music options. Yamaha's AV Setup Guide app for compatible tablets takes you through the connection process step-by-step, with visual aids to guide you. YPAO speaker calibration uses a microphone to measure your room's acoustics for optimal speaker performance.