The 120mm Silenx fan is stated as having an airflow of 58CFM at 1800rpm and only 14dBA. Is this correct? Seems a little optimistic to me
I have no idea whether those numbers are correct, or just numbers printed on a web page, but I've tried some semi-objective comparisons between the 120mm Silenx fan and my current favoured fan (Papst 4412).
The Silenx fan achieves it's silence by requiring the use of an additional cable which presumably drops the voltage.
I compared the airflow of the two fans by placing them facing each other with a piece of paper suspended between the two. I then varied the voltage to one of the fans (using a Fanmate) until the paper hung vertically. I'm making the assumption that in this state the airflow is roughly equal.
With the Silenx using the supplied voltage reduction cable, the airflow of the two fans was balanced with the Papst at a voltage of 8.5V. At this voltage the noise made by the two fans was equal in my estimation.
Removing the resistor widget and plugging the Silenx directly into 5V it was balanced by the Papst at 7.2V. Again the noise level was about equal.
To get the Silenx fan to equal the airflow of the Papst at 5V I had to supply it (the Silenx) with 3.65V. Yet again, the noise level was subjectively equal.
The quality of the noise made by the two fans was noticeably different, especially at lower voltages. The Silenx had more of a propellory sound (if that makes sense), whereas the Papst sounded more like bearings rubbing. In my personal
estimation the Papst was less offsensive, but that was literally with both fans stuck next to my ears, not fitted to a working PC. In use I'd doubt there was any practical difference.
So there you go. Conclude from that what you will. My conclusion is that the Silenx moves more air at a given voltage, but the same air at a given noise level.
I'm sticking with my Papst!