Noctua NF-A14x25r on a radiator. Tested with DIY frame

Ľubomír Samák

1 month ago

What we have arrived at

Due to the atypical spacing of the mounting holes for its format, the new Noctua NF-A14x25r G2 PWM fans cannot be installed in 140mm positions as standard. You need a conversion frame for that, and one such frame was designed, made and sent to us by an HWCooling reader. So, we were able to simulate and test one of the most anticipated fans of recent years (NF-A14x25 G2 PWM) already now.

The new generation of 140 mm fans has already come out, but only “partially”. This in the form of the Noctua NF-A14x25r. While these have the same aerodynamic design as the more versatile NF-A14x25 G2 PWM, they are mainly tailored for use on tower cooler heatsinks that have their clips customized. Like the NH-D15 G2 cooler, for example. For most other applications, the mounting hole spacing (105 × 105 mm) corresponding to standard 120 mm fans is unsuitable.

Some cases with “dual” positions for both 120 and 140 mm formats will accommodate these fans, but if the typical hole spacing for 140 mm fans (i.e. 125 × 125 mm) is required, you’re out of luck. That is, until you reach for a frame to which you could attach the fan using 105mm holes and then install the frame itself using 125mm holes.

A reader nicknamed “the patient” sent us such a frame. They also designed the frame themselves, and the source files for the 3D model are public. You will be able to print the frame yourself, if it makes sense to you. It fits not only the Noctua NF-A14x25r G2 PWM fan, but also other 140mm fans that use the 105×105mm hole spacing.

Basically, it is a 5 mm thick sheet with outer square dimensions of approximately 137.5 mm per side. The inner circle has a diameter of 132 mm. Depending on the material used and the 3D printing itself, it is possible that these dimensions will vary slightly. In the case of the Fiberflex 40D piece we received, we can say that it fits well and holds its position well with the fan as well. This despite the fact that the elasticity of the material is high, but at least it does not crack during screwing, which would reduce the mechanical durability of the whole solution. On one side of the frame, there are also well-modeled holes for recessing the screw heads.

Admittedly, a 4mm wider opening wouldn’t hurt (the frame walls wouldn’t interfere with the Stepped Inlet Design steps), but this one still avoids the axis of the blades, which is the main thing from a performance point of view.

The test results will differ somewhat with the results of the “September” square-frame fans for a number of reasons. We mentioned one in the previous paragraph, and then there’s something else. Although the frame, when installed on radiators, seals well in the most critical places, around the fan mounting holes, there will still be some leaks through which pressure will be lost. These are due simply to the frame being perched on anti-vibration pads, which are the highest points of the fan tunnel. This means that there is a narrow gap on the sides, which is not the case with the NF-A14x25 G2 PWM models. For the reason that these fans will have a full-circuit gasket pre-installed. This compensates for any height differences with a view to avoiding a drop in static pressure and thus airflow through an obstacle. For example, through a radiator. But the latter will be only one of the three obstacles which we will test with the frame on the NF-A14x25r G2 PWM. The others are a plastic filter and a hexagonal grille.

Different results than with the fans with originally a square frame (NF-A14x25 G2 PWM) are also obtained with this combination with the DIY frame due to the different impeller to obstacle clearance, which in this case is larger by the thickness (5 mm) of the frame. Theoretically to a positive direction (greater separation of the leading edges from the obstacle typically on a plastic filter and grille reduces unwanted microturbulence and thus reduces noise with simultaneously higher airflow), but practically it should be noted that the frame used by us does not represent any “optimization” for the NF-A14x25e G2 PWM, and on the contrary is characterized by features that can degrade the performance-acoustical characteristics. And that’s whether it’s a collision with the SID or other imperfections, such as unwanted grooving of the tunnel’s inner wall, which is a result of the natural manufacturing process of 3D printing by layering.

The tests are following the standard methodology, in the standard wind tunnel, but with a non-standard number of only one piece. We don’t have more NF-A14x25r G2 PWM fans, so keep that in mind. We’ll find out how one piece might differ from another later, comparing 15 samples following the same template as this test of the inexpensive Endorfy Stratus 120 PWM fans. But don’t write that to Noctua yet, lest they start making a selection of “better pieces”. 🙂

If you’re interested in details of the new Noctua NF-A14x25 G2 PWM fans, you’ll find them in this article.

Results: Airflow through a plastic filter

Why is there a missing value sometimes? There may be more reasons. Usually it is because the fan could not be adjusted to the target noise level. Some have a higher minimum speed (or the speed is low, but the motor is too noisy) or it is a slower fan that will not reach the higher decibels. But the results in the graphs are also missing if the impeller is brushing against the nylon filter mesh. In that case, we evaluate this combination as incompatible. And zero in the graphs is naturally also in situations where we measure 0.00. This is a common occurrence at extremely low speeds with obstructions or within vibration measurements.

Results: Airflow through a hexagonal grille

Results: Airflow through a thinner radiator

So we have the results of the NF-A14x25r G2 PWM fan with the DIY frame through the obstacles. It is important to emphasize “with the DIY frame”. As tempting as it may be to assume similar results to the square fan variant, it should be pointed out that the tested frame never came into contact with this fan during the design process and no optimizations were made to achieve the best possible results.

With frames like the Noctua NA-IS1, if the NF-A14x25r fan was supported, more favorable results would certainly be achieved. To what extent is hard to estimate, and we won’t even tell you now how much more favorable the results would have been without this frame – with a completely Noctua-directed solution. This will soon be represented by fan variants with circular bezels with the standard spacing that 140 mm fans normally have.

What we can state right away is, also in light of the current circumstances of the non-optimized DIY frame, the top-notch airflow through the radiator. Of the fans tested, only the Thermaltake Toughfan 14 Pro achieves higher airflow at comparable noise levels. Always, across the entire speed spectrum.

At lower speeds and therefore lower noise, the NF-A14x25r G2 PWM fan with our frame usually finishes in second place. It drops a rank or two with higher speeds, but most users will probably be interested in the lower and very low noise levels. In those, as you know, the TT Toughfan 14 Pro can also be disqualified by its higher tolerances on quality characteristics, where some pieces somewhat… “rattle”, which we also pointed out in our standard analysis. With the Noctua NF-A14x25r G2 PWM, similar concerns are most likely out of the question, and you probably won’t have to rummage through these fans to get to “quieter” pieces. We’ll confirm (or disprove) this assumption later in a comparison of several pieces in a higher-than-standard quantity.

Worrying about how to mount the Noctua NF-A14x25r G2 PWM on a radiator doesn’t make much sense at the moment (even if you have the 3D model of the frame available that you can just print out), but that’s only because the release of the square frame variant is a matter of the next weeks or days. And mounting it in a case for system cooling? Preliminary results with the plastic filter don’t look that great, but again – the DIY frame may be spoiling it for the Noctua NF-A14x25r G2 PWM fan due to its properties.

On the grille, the situation is considerably more favourable. The Noctua fan returns again to the second place, which it doesn’t let go even at relatively higher speeds. In this case, the main rival is not the Thermaltake fan (the grille is a weak discipline for the Toughfan 14 Pro), but the Arctic P14 PWM PST. The differences are very small and you probably can’t rule out the NF-A14x25 G2 PWM fan (i.e. the variant with its own square frame) erasing them. But it also might not, and our combination could theoretically achieve better results. This is because of the greater separation of the impeller from the grille, which is given by the thickness of the conversion frame.

So, for now, like this, partially. As far as fans are concerned, the soonest we will hopefully meet is a complete analysis of the variant (NF-A14x25 G2 PWM), to which we won’t have to add anything to mount it on the obstacles.

English translation and edit by Jozef Dudáš

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