Receiver/Amplifier 12 Volt Trigger-Controlled Cooling Fans/Enlarged Airchamber Bases & multispeed These two high-quality, super low noise 80mm fan units are designed sit on your component's top air vents. Each fan has a special raised air-chamber base, which covers nearly twice the area of a standard fan. A vortex of air is pulled out of the top of your component over the full area of these raised bases. In addition, you control the speed of the fans, with the multi-speed power controller. 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. 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 two fans (running together) are rated at 13db while moving 31 cubic feet of air per minute at 1/2 speed, or 16db & 41CFM at 2/3 speed. With component cooling, slow (and quiet) are the way to go! Other available speeds: 1/4 speed = 10db/16CFM, 3/4 speed = 19db/46CFM, full speed = 22db/62CFM.