Logitech Speaker System Z623. For big, bold, 2.1 sound. THX Certified means quality you can count on-these speakers have met strict performance standards to achieve THX certification. You'll hear-and feel-immersive audio from 200 watts (RMS) of power that brings music, movies, and games to life. Multiple inputs-and a built-in headphone jack-make it easy to get great sound from up to three audio devices. Easy, two-satellite setup and a powerful subwoofer give you big sound-even in large spaces. And integrated controls put you in command-dial the volume and bass up or down to customize your listening experience.