Superbase Receiver/Amplifier 12v Trigger-Controlled Multi-Speed Cooling Fan This 120mm Super-base fan unit is designed sit on your component's top air vents, and it provides serious cooling at an economical price. It has a special raised air-chamber base, which covers over 50 square inches of your component's top vents. Hot air is removed from your component over the full area of this large raised base, which causes cool air to be pulled up from the bottom vents. The system has a 12 volt trigger control module, which turns the fans on and off, by monitoring your receiver's 12v trigger socket. This module sends power from the multi-voltage transformer (included in the system), which runs the fans. IMPORTANT: Some receivers have a non-standard setup, where the receiver doesn't directly control the trigger (for example, the trigger might be under the control of Zones 2 or 3, etc.). Please consult your receiver's manual for details about how its 12v trigger operates, or contact me if you have questions. In addition, you control the speed of the fan, with the 5-speed power controller. The Superbase cooling unit measures 7-1/2" square. Recommended fan speeds for this system: The fan is rated at 10db while moving 25 cubic feet of air per minute at 1/3 speed, or 13db & 37CFM at 1/2 speed. With component cooling, slow (and quiet) are the way to go! Other available speeds: 2/3 speed = 16db/49CFM, 3/4 speed = 19db/55CFM, full speed = 22db/74CFM.