Best quiet case fan

Solution


Note that you have to be very careful with the ML Pro fans. If you connect them to the wrong type of header, or the right type of header with the wrong implementation, you can destroy the bearings in those fans. The damage occurs over time, usually. Power outages can take them out in one...
Best option right now IMO are the Corsair ML series 120 and 140 mm fans. Not sure how much you know about them, but they're the first PC fans using maglev technology and they're much quieter due to no contact with the bearings. Been using them myself for about 6 months and they're great.

I think right now you can get a pack of 2 of the 120mm fans in the ballpark of what you're willing to pay, while the 140mm variant goes for about $25 each.
 


Note that you have to be very careful with the ML Pro fans. If you connect them to the wrong type of header, or the right type of header with the wrong implementation, you can destroy the bearings in those fans. The damage occurs over time, usually. Power outages can take them out in one fell swoop, just like an improperly installed water pump.

It's enough of a pain to ensure they'll work that I hesitate to recommend them, even though they perform very well when you do your homework and install them correctly.
 
Solution


Useful point to note! I don't think it's so much an issue on modern mobos, as they should all have sufficient PWM headers, but this could be an issue on some older boards.
 


Gigabyte and MSI both use incorrect implementations of their 4-pin case fan headers on their Z270 boards. They don't even bother connecting the fourth pin. Some other manufacturers also do this, but I haven't gone through the manuals for ASRock or EVGA recently.

The only consumer motherboard manufacturer that I've encountered that actually puts real 4-pin circuitry on all of their headers is Asus.