When you start up a Power Mac G4 Cube computer there is a delay of approximately five to seven seconds before the startup sound is heard through the Apple USB Speakers. This is normal. The Power Mac G4 Cube computer does not have an internal speaker, so the startup sound is routed through the Universal Serial Bus (USB) whose drivers are not available until after the computer is turned on.
If no speakers are connected to a USB port, only the power light indicates that the computer has been turned on.