If you connect the Fifth Generation iPod (iPod with video) running iPod Software 1.0 to an iPod Hi-Fi, the Speakers menu will have a Room Size option instead of Tone Control.
Apple only supports using the Speakers menu on the Fifth Generation iPod when it is running iPod Software 1.1 or later. If the Speakers menu has a menu option of Room Size, update your Fifth Generation to iPod Software 1.1 or later to work correctly with the iPod Hi-Fi.