Summary: I know noctua make the best fan. i have had their other fans and they are super quiet with great airflow. However, this one is noisier at the same airflow as the other nocuta fans i have. Wish i had known this before purchase because now i am unhappy i spend the money on these. I bought these cause they were a few dollars cheaper. don't buy these at this price. if they were 10 then it would be worth it.
Summary: I like Noctua's P12 and F12, but the S12 has about the worst noise to airflow ratio I've ever encountered. At anything other than the lowest speed, it emits a loud whirring. At top speed it screams while pushing air hardly justifying the volume, making me almost feel pity for it. 18.1dba is Noctua's claim for full speed, 1200rpm, but it's closer to 30db. These fans have a psychological effect on some buyers: they're noctua, hence they must be silent.
Summary: I returned it. It is noisy (IMHO) and does not provide much static pressure. Definitely not for CPU cooling. Not sure it would compare much more favorably as a case fan as I find it noisy (not sure if we are allowed to make direct product comparisons here, but google for 120mm fan reviews and that will give you more info). IMHO the FLX is a pass. PS: "noisy" seems to be a relative thing, as others rated it as silent...
Summary: Nachtrag: Die Gummihalterungen lassen sich nicht richtig anbringen. Sie sind so flexibel, dass man sie nicht reindrücken kann sondern reinziehen müsste. Dies ist jedoch je nach Gehäuse nur mit Ausbau der Komponenten (Mainboard usw. ) möglich. Die Unwucht des Lüfters ist leider kein Einzelfall. Ich habe drei dieser Lüfter erworben. Alle drei haben dieses Manko :-(( Die Verpackung ist ökologisch gesehen bedenklich.