Bitfenix Whisper Series 550W PSU Review

Efficiency, Temperature, And Noise

Efficiency

Our efficiency testing procedure is detailed here.

Using results from the previous page, we plotted a chart showing the BWG550M's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.

The BWG550M achieves very high efficiency under both light and normal loads. CWT's GPU platform looks great so far!

Efficiency At Low Loads

In the following tests, we measure the BWG550M's efficiency at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20, 40, 60 and 80W. This is important for representing when a PC is idle, with power-saving features turned on.

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed
Fan Noise
PF/AC Volts
11.210A0.490A0.477A0.195A19.6675.85%340 RPM
21.0 dB(A)
0.805
12.063V5.063V3.344V5.087V25.92115.1V
22.443A0.978A0.985A0.390A39.6883.93%340 RPM
21.0 dB(A)0.911
12.057V5.060V3.341V5.083V47.28115.1V
33.685A1.475A1.495A5.078A59.8787.24%340 RPM
21.0 dB(A)0.947
12.053V5.058V3.339V5.078V68.63115.1V
44.914A1.973A1.975A0.785A79.7688.83%400 RPM
21.3 dB(A)0.964
12.050V5.055V3.338V5.073V89.79115.1V

Efficiency under light loads is amazing! Even with 20W applied, this PSU easily passes 75%. And with >40W loads, the 80% mark is easily achieved.

In addition, the minimum fan speed is restricted at 340 RPM, where noise output is imperceptible.

5VSB Efficiency

The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher efficiency with 100mA of load, 60 percent or higher with 250mA of load, and 70 percent or higher with 1A or more of load.

We take four measurements: one each at 100, 250 and 1000mA, and one with the full load the 5VSB rail can handle. 

Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts
10.101A0.5173.91%0.065
5.093V0.69115.1V
20.252A1.2878.53%0.144
5.090V1.63115.1V
31.002A5.0878.15%0.343
5.072V6.50115.1V
42.502A12.6175.69%0.448
5.038V16.66115.1V

The 5VSB rail has really good load regulation, though we'd like to see at least one reading close to or over 80% in the efficiency section.

Power Consumption In Idle And Standby

In the table below, you'll find the power consumption and voltage values of all rails (except -12V) when the PSU is idle (powered on, but without any load on its rails), and the power consumption when the PSU is in standby mode (without any load, at 5VSB).

Mode12V5V3.3V5VSBWattsPF/AC Volts
Idle12.059V5.068V3.347V5.096V4.040.274
115.1V
Standby0.070.007
115.1V

Standby power consumption is very low, as you can see in the graphs above.

Fan RPM, Delta Temperature, And Output Noise

Our mixed noise testing is described in detail here.

The first chart below illustrates the cooling fan's speed (in RPM), and the delta between input and output temperature. The results were obtained at 34°C (93.2°F) to 46°C (114.8°F) ambient temperature.   

The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measured acoustics from one meter away, inside a small, custom-made anechoic chamber with internals completely covered in sound-proofing material (be quiet! Noise Absorber kit). Background noise inside the chamber was below 18 dB(A) during testing, and the results were obtained with the PSU operating at 34°C (93.2°F) to 46°C (114.8°F) ambient temperature. 

The following graph illustrates the fan's output noise over the PSU's operating range. The same conditions of the above graph apply to our measurements, though the ambient temperature was between at 28°C (82.4°F) to 30°C (86°F).  

This is a really quiet PSU. For the majority of its operational range, output noise is kept under 25 dB(A). Even in a worst-case scenario, the noise doesn't exceed 31 dB(A) under normal thermal conditions.

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6 comments
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  • turkey3_scratch
    Bitfenix did the right thing pairing with CWT here. This is a great unit!
  • Aris_Mp
    Indeed, its performance was a nice surprise for me as well. It's good to see some new competition in this market.
  • Nuckles_56
    Damn, I wonder what Australian pricing will be like for this unit, as I'd be almost tempted to replace my current PSU with a quieter one like this if it is priced well
  • MarekRMac
    Hi, please give me quick advice: Bitfenix Whisper M 550W or Corsair RM550x ?
  • Aris_Mp
    2391142 said:
    Hi, please give me quick advice: Bitfenix Whisper M 550W or Corsair RM550x ?


    Which ever you can find at a lower price. Performance wise they are very close.
  • jonnyguru
    One noticeable difference between the RMx and the Whisper is that the RMx uses an MCU for the fan controller instead of the standard thermistor/transistor circuit in the BitFenix product.