How we measure power draw and motor power
The Silent Wings (Pro) 4 represent the pinnacle of computer fan range. The non-Pro variants stand out especially in system positions and are not well suited for radiators. This is by design and in line with the sort of “micro-segmentation” of BeQuiet. In a white design, like the one tested, it will be quite difficult to find other 140 mm fans that are quieter at comparable airflow.
How we measure power draw…
Is it worth addressing the power draw of fans? If you have seven of them in your computer (three on the radiator of the cooler and four for system cooling in the case) and they are also backlit, the power draw starts at tens of watts. This makes it worth dealing with.
All fans are powered by Gophert CPS-3205 II laboratory power supply. It is passive and virtually noiseless, so it does not distort our noise level measurements. However, for the PWM fans, a Noctua NA-FC1 controller is connected through which the fans are regulated. We also have a shunt between the power supply and the Noctua controller. On it, we read the voltage drop, from which we then calculate the current. However, the voltage on the power supply is set so that 12 V goes to the Noctua NA-FC1. We then also set the exact 12 V to measure the maximum power of the 3-pin linear power supply fans.
In the power draw tests, we will be interested in the power draw in fixed noise level modes in addition to the maximum power consumption at 12 V or 100% PWM. That is, at those settings at which we also measure other parameters. Finally, in the graphs you will also find the power consumption corresponding to the start-up and minimum speeds. The difference between these two settings is that at start-up speed you need to overcome the frictional forces, so the power draw is always higher than at minimum speed. At these, the fan is already running and just reduces power to just before a level where it stops.
These start-up and minimum power draw data are a substitute for the start-up and minimum voltage information. You often encounter this when reading about fans, but with PWM fans there is no point in dealing with it. And although it is possible to power a PWM fan linearly, it will always perform better with PWM control – lower starting and minimum speeds. Therefore, it would be unfair to compare these parameters for all fans using linear control. That way, fans with PWM would be disadvantaged and the results distorted.
…and motor power
In addition to power draw, it is important to consider one more parameter that is related to the power supply – the power of the motor. This is usually listed on the back on a label and is often mistaken for power draw. However, the voltage and current indication here is usually not about power draw, but about the power of the motor. The latter must always be well above the operating power draw. The higher it is, the longer the life expectancy of the fan.
Over time and with wear, fan friction increases (through loss or hardening of the lubricant, dust contamination or abrasion of the bearings, etc.). However, a more powerful motor will overcome the deteriorating conditions of the fan to some extent, albeit at a higher power draw, but somehow it will cope. However, if the difference between the motor power and the operating power draw of a new fan is small, it may no longer be able to exert sufficient force to turn the impeller under increased friction due to adverse circumstances.
To test the power of the motor, we set the fan to full power (12 V/100 % PWM) and increase the mechanical resistance by braking the impeller in the middle. This is a higher load for the motor, with which the power draw naturally increases. But this is only up to a point, until the impeller stops. The power of the motor in our tests corresponds to the highest achieved power draw that we observed when the fan was being braked.
We use the Keysight U1231A high sample rate precision multimeters to analyse motor power (as well as normal operating power draw). In addition, the individual samples are recorded in a spreadsheet, from which we then graph the maximum. The final value is the average of three measurements (three maximums).
- Contents
- BeQuiet! Silent Wings 4 (BL117) in detail
- Overview of manufacturer specifications
- Basis of the methodology, the wind tunnel
- Mounting and vibration measurement
- Initial warm-up and speed recording
- Base 6 equal noise levels…
- ... and sound color (frequency characteristic)
- Measurement of static pressure…
- … and of airflow
- Everything changes with obstacles
- How we measure power draw and motor power
- Measuring the intensity (and power draw) of lighting
- Results: Speed
- Results: Airlow w/o obstacles
- Results: Airflow through a nylon filter
- Results: Airflow through a plastic filter
- Results: Airflow through a hexagonal grille
- Results: Airflow through a thinner radiator
- Results: Airflow through a thicker radiator
- Results: Static pressure w/o obstacles
- Results: Static pressure through a nylon filter
- Results: Static pressure through a plastic filter
- Results: Static pressure through a hexagonal grille
- Results: Static pressure through a thinner radiator
- Results: Static pressure through a thicker radiator
- Results: Static pressure, efficiency depending on orientation
- Reality vs. specifications
- Results: Frequency response of sound w/o obstacles
- Results: Frequency response of sound with a dust filter
- Results: Frequency response of sound with a hexagonal grille
- Results: Frequency response of sound with a radiator
- Results: Vibration, in total (3D vector length)
- Results: Vibration, X-axis
- Results: Vibration, Y-axis
- Results: Vibration, Z-axis
- Results: Power draw (and motor power)
- Results: Cooling performance per watt, airflow
- Results: Cooling performance per watt, static pressure
- Airflow per euro
- Static pressure per euro
- Results: Lighting – LED luminance and power draw
- Results: LED to motor power draw ratio
- Evaluation
Is the very low speed characteristics similar to that observed in CPS RZ120?
This fan would have been much more competitive if it were to have closed corners by default. The corner swapping gimmick doesn’t seem to offer any actual benefit to me, as the vibrations are already low and similar results in dampening could already be achieved by using rubber mounts. They definitely could have saved some cost and/or priced the fan even more competitively by using integrated, closed corners instead of this gimmicky design.
That said, for users willing to DIY, this should still be a great radiator fan. All you need is some tape to seal up the corners, saving you quite a bit of money.
I mean the F5 R120. Confused with the cooler names.
Yes, if you encounter a lower airflow at the same noise level, a similar characteristic (as with the Silent Wings 4 BL117) is also found in the F5 R120. More fans have this. At such low speeds, the non-aerodynamic sounds must be extremely quiet to leave room to set the speed high enough for leading rankings.
Replacing the corners of the BL117 is really useful if only just to be able to install this fan on a radiator of a liquid cooler, where the SW4 doesn’t make much sense. Although the SW4 doesn’t need to be smeared too much in this scenario. Sure, due to the significant drop in placement compared to other fans, the urge is there, but at higher speeds it even outperforms the NF-A14. Sure, for a fan with modern geometry it’s more of a failure, but…
Using tape to seal the corners is a good DIY “trick”. 🙂
How would you compare it to the Pure Wings 3? This fan seems to constantly get outperformed by its cheaper sibling. The Pure Wings 3 does have a lower RPM limit, but there doesn’t seem to be other major disadvantages by going for the Pure Wings instead.
Now I’m really curious how the high speed, 9-blade version of the Pure Wings 3 performs.
The 140 mm Pure Wings 3 with 7 blades often seems to be a balanced (and a hair more more efficient) solution like the Silent Wings 4 (BL117). Although we have the SW4 in the white variant, which probably tends to be a bit noisier. These small differences (in tonal peaks) do not show up on radiators, where the tested PW3 variant has a significant advantage for obvious reasons (good sealing corners). We are also curious about the 9-blade Pure Wings 3 in 140 mm format. We will probably get to it after the announced Arctic P14 triple fan test (PWM PST, PWM PST CO and Max). 🙂
The Pure Wings 3 has a MTBF of 60 000 hours, which can be a disadvantage compared to Silent Wings 4 (with 300 000 hours). Lower robustness of critical parts in terms of durability (or change of properties over time) can also be indicated by the smaller impeller hub (of the PW3 BL108) and also at higher speeds relatively higher vibrations (again of the PW3 BL108), which could also indicate higher manufacturing tolerances. Of course, these vibrations could also be due to vibrations on the blades, but I assume they will be composed of several sources. And one of them will be related to the quality level of the impeller centering.
I guess the P14 trilogy will be consecutive releases then.
It’s a shame that we can’t have a Silent Wings 4 that comes with sealed corners, otherwise we’d have a reliable (and strong performing) 14 cm fan in the ~20$/£ price range that would compete very favourably vs. the Noctua A14 for example. I guess that’s done to prevent cannibalising their sales of their own flagship, but I’m not sure if it’s a smart move given the tough competition…
Yes, the next test will be the P14 PWM PST CO and I will conclude the trilogy (on Monday?) with the Max model.