Antec ISK 300-65 Mini-ITX Case

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Stock Fan Measurements

The stock fan is an Antec TriCool 80x25mm double ball bearing fan with seven blades and the now familar 3-position switch. The speed switch is attached via cable to the fan, and is held to the back of the case with two small screws. The geometry is not good: The blades' trailing edges are nearly parallel to the three struts, which suggests that the noise generated will have high tonal aspects.

Stock Antec TriCool 80x25mm double ball bearing fan

The fan was measured while mounted in the Antec ISK-300 case with the cover on. The case was placed at the edge of a table in the anechoic chamber. Two sets of SPL measurements were performed, one at 1m as usual, and another at 0.6m, at the ISO 7779 (PC noise measurement standard) seated user position. The ISO 7779 seated user position SPL measurement will be conducted with PCs and cases that are likely to be placed on the desk near the monitor, as it is more relevant than the 1m distance usually used.

Stock Fan Measurements (Baseline Noise)
Switch position
High - 5V
High - 4V

At all but the lowest speeds, the stock fan was not quiet. It had serious tonal elements at all speeds, even at the low setting. A kind of whispery high pitch sound underlay the normal wind turbulence noise, sounding at times like distant chirping of many crickets. It became very annoying over time. When manually undervolted, the fan speed could be reduced further for improvements in noise, but the airflow seemed too diminished to be useful. The minimum start voltage was 4V with the switch set on high.

The green arrows point to the tonal aspects of the sound with the fan set to low, measured from a meter away. The peak near 4kHz is probably the annoying whispery high pitched noise, which is present at virtually every fan speed, even as far as a couple meters away.

This frequency spectrum was captured with the microphone 0.6 meters away, a typical seated user distance. The fan was set to a very low speed, with 5V, speed switch on high. From a meter, it measured only 13.5 dBA. That ~4kHz peak persists here, and it's plainly audible.

Could the acoustic performance of the fan be caused by bearing damaged in transit? Possibly but unlikely. There was no indication of any bearing damage that we could identify. It simply appears to be a fan of poor acoustic quality. It's the only noise source in the case; why not spend a dollar or two more on a better fan when it's so critical for overall acoustics?!

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