Receiver/Amp Megabase 12 Volt Trigger-Controlled Cooling Fans/multispeed Control / 12v This super low-noise dual-120mm fan unit is designed to sit on your receiver's top air vents. It has a special raised air-chamber base, which covers 145 square inches, and air is drawn out over the entire area of this raised base. The system includes a 12 volt trigger control module, which turns the fan on and off, under the control of your component's 12v trigger socket. The 12v module controls the power from the cooling system's multi-speed transformer, directing it to the fans when it detects a 12v signal. In addition, you control the speed of the fans, with the multi-speed power controller. 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. Recommended fan speeds for this system: The fans (running together) are rated at 13db while moving 50 cubic feet of air per minute at 1/3 speed, or 16db & 72CFM at 1/2 speed. With component cooling, slow (and quiet) are the way to go! Other available speeds: 2/3 speed = 19db/98CFM, 3/4 speed = 22db/110CFM, full speed = 25db/148CFM. The Megabase cooling unit measures 14.5" wide, and 10" deep. It is 1-1/2" tall, and only requires about 1/4 inch of additional space above for airflow.