I have seven 12v ball bearing cooling fans each with their own AC/DC power adapter.
Four of them have six different voltage settings (so six speed fan) and the other 3 are fixed at 9v (one is 9.4v) for quietness.
I made these using spare parts that I have laying around. The connections are soldered, individually heat shrink wrapped then another layer of shrink wrap on top of that. Two of the fans are identical while others are all a bit different from each other. The ones with the variable voltage power adapter moves the most air while the other three move about the same to each other but less velocity than the four running at 12v. The power adapters all make more power than the fan needs, some more than double the power so no worry about overheating. These can be used to cool anything in your house, home theater receivers, amplifiers, component cabinets, TVs... anything that needs cooling to prolong its life. You can even use it as a tiny desk fan if it needs to be.
4. Price: :
1 - 80mm (3 1/8") fan, variable speed, 5 feet cord - $15 shipped
2 - 80mm (3 1/8") fan, variable speed, 5 feet cord - $15 shipped
3 - 80mm (3 1/8") fan, variable speed, 5 feet cord - $15 shipped
4 - 70mm (2 3/4") high speed CPU fan, variable speed, 5 feet cord, $15 shipped
5 - 60mm (2 3/8") high speed CPU fan, fixed speed, 4 1/2 feet cord, $10 shipped
6 - 80mm (3 1/8") fan, fixed speed, ultra quiet (9.4v), 5 feet cord, $10 shipped
7 - 60mm (2 3/8") high speed CPU fan, fixed speed, 6 feet cord, $10 shipped
I would take trades, let me know what you got. Want them all for a trade? Sure. They all work very good.