The basis of the methodology, the wind tunnel
To write that we have something mapped out to the last detail is perhaps too bold, but after proper preparation, few pieces of hardware are as easy to evaluate as fans. Of course, this had to be preceded by long preparations, developing a methodology, but you already know the story. What you don’t know yet is the first fruit, or rather the results of Akasa, SilentiumPC, SilverStone, Xigmatek or more exotic Reeven fans.
The basis of the methodology, the wind tunnel
Before you start reading the methodology with all the details, take a look at the test tunnel as a whole. This is the heart of the whole system, to which other arteries are connected (manometer, vibrometer, powermeter, …). The only solid part of the tunnel from the measuring instruments is the anemometer.
The shape of the wind tunnel is inspired by the Venturi tube, which has long been used to measure the flow of liquids and gasses. The Venturi effect for wind speed measuring is also known from the aerospace industry. However, the design for measuring computer fans has its own specificities, which this proposal of ours reflects.
The individual parameters of the HWC wind tunnel for fan tests are the result of physical simulations and practical debugging. All the details (folds, material or finish used) have a rationale behind them and are designed this way for a specific reason. We will discuss the individual design details in turn in the description of the sub-variable measurements.
Now we will briefly elaborate on some things that do not fit thematically into the text of the following chapters. Namely, for example, that the skeleton of the wind tunnel is the work of a 3D printer (PLA). The rough print was, of course, then thoroughly machined by grinding, fusing, polishing and varnishing. Especially important is the smooth finish of the interior walls.
When joining the individual parts, the emphasis was on making sure that they fit together flawlessly, that they were sealed flawlessly (we will come back to this when we describe the test procedures for pressure measurement), but also that the joints were not loosened by use. Everything is disassemblable for servicing purposes, but it is ensured that the properties are maintained during use and, for example, even under the stress of vibration. The threads are secured with either lock nuts or thread-locking fluid. It depends on which is more suitable in which place.
When the wind tunnel is not in use, it is enclosed in a dust-tight chamber. In addition to the technical equipment and its correct storage, it is also important for objective outputs that all measuring instruments are calibrated according to the standard. Without this, it would be impossible to stand behind your results and rely on the manufacturers’ specifications. Calibration protocols are therefore an important part of the methodology. Testing is carried out at an ambient air temperature of 21–21.3 °C, humidity is approximately 45 % (± 2 %).
Fans come to us for testing in at least two pieces of the same model. If the deviations of any of the measured values are greater than 5 %, we also work with a third or fourth sample and the average value is formed by the results of the fans that came out the most similar and the differences between them fit under 5 %.
- Contents
- BeQuiet! Silent Wings 3 (BL066) in detail
- The basis of the methodology, the wind tunnel
- Mounting and vibration measurement
- Initial warm-up and speed recording
- Base 7 equal noise levels…
- .. and sound color (frequency characteristic)
- Static pressure measurement…
- … and 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 by 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
I have this fan as a part of the Dark Rock Pro 4 cooler – the front one. The inner fan is disabled for now. Unfortunately, I am thinking about replacing it. What’s driving me completely nuts is the fan start that gives a sound resembling powerful rubbing against a rough surface. It’s okay for folks who want to have the fan running constantly and encounter it only during boot but I want to have a fanless idle – 0 noise, no vibrations, extended fan life, and lower power draw. I wish such behavior was stressed in this and other reviews so that one can find safe alternatives for such requirements.
It’s a pity to encounter such an unexpected drawback, as this fan is much quieter than Arctic P12. At 700 RPM, it’s barely audible in my Nanoxia Deep Silence 8 in the night, and below 500 RPM basically inaudible.
What you are describing is happening with several fans. To an excessive degree with the Strix XF120 as well, where we also mentioned it. I have thought about how to measurably grasp those starts in the context of the interpretation of the results so that a simple comparison across fans is possible, but I don’t know yet.. anyway, it will probably be an initial phase with rotor centering, which is accompanied by higher vibrations in addition to the acoustic expression.
Perhaps the evaluation page can be divided into several labelled subsections, one being dedicated to observations like this for example.
My P14 Slim rev.1 does this initially too, but it’s gone now after I have mounted it tight. Perhaps quality control and tolerance also play a role here?
Maybe we are each talking about a slightly different phenomenon. The initial, let’s say start-up sound of Strix XF120 will certainly not be influenced by the strength of the mounting. With this fan, it’s just that it takes some time (be it very short, in the lower units of seconds) to get centered, and the operational sound is probably a bit different after, let’s say, warming up. I would attribute this purely to the influence of the motor and the bearings. In this case, I would not talk about an issue of a single unit in serial production. Sure, within lower manufacturing tolerances some minor differences in behaviour can be present, but if that feature disappeared completely, I assume it would be due to larger, targeted changes in the design, which for example are solved by various revisions. Unfortunately, most manufacturers don’t talk about them, with a few exceptions (Arctic, for example). So sure, a Silent Wings 3 from the early batches may behave differently than the latest pieces from the current sales. And while we’re on the subject of fan differences from piece to piece, we’ll release one unconventional test in September that will be of interest to you. 🙂
I would rather attribute the different sound after tightening the P14 rev. 2 to vibrations and the fact that with a different mounting there may not be such significant resonance frequencies of the case.