Hi all,
Here's my testing on the Noctua NF-A6x25 FLX versus the Papst 812L (from my No.2 3245A).
I held each of the fans up against my 3D printed jig so that all airflow is directed through the anenometer.
NOCTUA:12V = 2.9 m/s blowing through jig
15V = 3.8 m/s blowing through jig
15V = 2.9 m/s suction through jig
61dBA (@ 15V) which includes background noise.
PAPST:12V = 1.5 m/s blowing through jig
15V = 1.8 m/s blowing through jig
15V = 2.9 m/s suction through jig
64dBA (@ 15V) which includes background noise.
There must be an airflow/obstruction/resistance thing going on, because the Papst seems almost the same if not slightly more powerful on an in-the- face test, but the blowing-through tests don't seem to back that up......but the suction tests do!
3dBA difference so exactly half the volume for the Noctua (for the human ear). Value measured at 1" distance from side of fan (thus not affected by airflow)
The Papst fan seems to have a lot more torque/weight/inertia, I guess thats why we hear that 3458A whine on power up as it gets up to speed.
Ian.