The Sonos Sub, not to be confused with the Five-Dollar Footlong, is a subwoofer that works wirelessly with the Sonos family of devices and adds considerable bass to any Sonos CONNECT:AMP, PLAY:5, or PLAY:3 device. It is a substantial device with two force-canceling speakers that outputs down to 25 Hz. At $699 this isn’t your run-of-the-mill audio purchase. However, the difference in sound reproduction with and without the Sub is quite striking.