The Be Quiet! SFX-L Power 500W PSU Review: Powerful, Small, & Still Quiet?

Hot Test Results

Earlier SFX PSU designs were notorious for their poor power quality figures. More recent models, like the SilverStone SX700-LPT and the Enermax Revolution SFX 650W, were greatly improved. Sadly, the electrical performance of the Be Quiet! SFX-L Power 500W may not be as bad as that of the earlier models but it definitely is not on par with these newer designs. Voltage regulation is excellent, with the 12V line maintaining a regulation of 1.1% and the 3.3V/5V lines falling only slightly behind at about 1.5%. Power quality however leaves a lot to be desired. While voltage ripple figures are well within the design guide limits, we recorded a maximum of 82 mV, 42 mV and 36 mV on the 12V, 5V and 3.3V lines respectively, figures that are high by today’s standards and uncomfortably close to the directive’s limits. Paradoxically, when the unit is heavily cross loaded, the main 12V line displays a ripple lower than that of the 3.3V/5V lines.

The Be Quiet! SFX-L Power 500W retains its high energy conversion efficiency inside the hotbox, taking only a relatively small performance hit evenly distributed across the entire load range. This indicates that the components are not getting thermally stressed, not even when the unit is heavily loaded under these adverse conditions. The average efficiency reduction is 1.1%, with a drop of 1.5% at 100% load, suggesting that the components are handling the adverse ambient conditions relatively well.

The presence of the 120 mm cooling fan hardly helps the acoustics performance of this PSU when the ambient temperature is very high. It makes the noise levels a little more tolerable when the PSU is heavily loaded, but the PSU will certainly not be quiet under such conditions, not with a load any higher than 100 Watts. Despite the deferential efforts of the cooling fan, the internal temperatures of the Be Quiet! SFX-L Power are relatively high for a PSU with a maximum output of just 500 Watts. With the components not showing any signs of thermal stress and the efficiency holding very well, the obvious culprit here again is the small heatsinks. 

As expected, the heatsinks of the SFX-L Power 500W PSU are too small for extreme operating conditions and, thus, the cooling fan is striving to cope with the high cooling requirements. The internal temperatures are kept at safe levels but the PSU is clearly audible even when lightly loaded, with the fan’s noise reaching intolerable levels  under high loads. As this unit is rated for operation up to 40 °C, we find these results unsurprising.