Airflow the FT9 SLIM delivers behind a dust filter and on a radiator, and its noise, over the whole rpm range. Every curve on this page is calculated from the manufacturer's free-air rating with the CaseCalc derate model. Nothing is measured; the shaded bands show the spread to expect.
| rpm | Open grille CFM | Dust filter CFM | Radiator 30 mm CFM | Shut-off mmH₂O | dB(A) |
|---|---|---|---|---|---|
| 500 min | 4.7 | 4.1 | 3.7 | 0.14 | <15 |
| 880 | 8.2 | 7.3 | 6.5 | 0.43 | <15 |
| 1180 | 11.0 | 9.7 | 8.7 | 0.77 | <15 |
| 1480 | 13.8 | 12.2 | 10.9 | 1.21 | <15 |
| 1770 | 16.5 | 14.6 | 13.1 | 1.73 | <15 |
| 2060 | 19.2 | 17.0 | 15.2 | 2.34 | 15.9 |
| 2360 | 22.0 | 19.5 | 17.4 | 3.07 | 18.6 |
| 2660 | 24.8 | 21.9 | 19.6 | 3.90 | 21.1 |
| 2950 | 27.5 | 24.3 | 21.8 | 4.80 | 23.3 |
Model values; the band is drawn in the charts above. Multiply CFM by 1.699 for m³/h. The fan does not run below 500 rpm; the table starts there.
From the datasheet's 4.80 mmH₂O shut-off pressure and 31.2 CFM free delivery at 2950 rpm, scaled by the fan laws (flow ∝ rpm, pressure ∝ rpm²) on a parabolic curve. Real axial fans have a dip in the middle of the curve that this shape does not show; the end points are the datasheet's.
From the datasheet's 23.2 dB(A) at 2950 rpm. At half speed (1475 rpm) the model gives under 15 dB(A), below the noise floor of a quiet room. Below about 15 dB(A) a fan is inaudible in a quiet room.
Delivered airflow is CFMfree air · derate · rpm/rpmmax. The free-air figure is the
manufacturer's. The derate is the share of it that survives the mounting; it does not depend on rpm because fan
pressure and flow resistance both scale with rpm². Airflow is therefore linear in rpm.
| Mounting | Airflow blades | Pressure-optimized blades |
|---|---|---|
| Open grille | 0.88 (0.80–0.95) | 0.88 (0.80–0.95) |
| Dust filter | 0.70 (0.60–0.80) | 0.78 (0.70–0.86) |
| Radiator 30 mm | 0.60 (0.47–0.76) | 0.70 (0.58–0.83) |
| Solid or glass front (side slits) | 0.50 (0.40–0.62) | 0.58 (0.48–0.68) |
The bands are the plausible spread of filter mesh density, radiator fin density and grille geometry. They are not statistical confidence intervals from measurements; they are the range the same fan lands in across typical cases.
Noise is the aerodynamic term Lmax + 50 · log₁₀(rpm/rpmmax) added on an energy
basis to a constant 6 dB(A) motor and bearing floor, so the curve flattens at low rpm instead of running to zero.
The band uses slopes of 40 and 60 dB per decade, ±1.5 dB on the rating and a 3 to 9 dB(A) floor. Manufacturer dB(A)
figures are not measured the same way across brands; differences under 3 dB between brands mean nothing.
Static pressure, where the datasheet gives it, is drawn as a parabola from the shut-off pressure to free delivery and scaled by the fan laws: flow ∝ rpm, pressure ∝ rpm². It is a shape between two datasheet points, not a measured curve; real axial fans dip in the middle.
Nothing here is measured. The values are what the fan laws and typical case resistances predict from the datasheet. Use them to compare and to size; expect a real build to land inside the band, not on the line.