Noctua NF-A12x15 Fan Review

Noctua has released a new 15 mm thick fan, named the NF-A12x15. It is designed to fit in skinny places and to provide relatively high static pressure. They faced challenges getting a fan this thin. For example, “For the 12cm NF-A12x15, a steel-reinforced motor hub and brass axle mount are being used in order to assure the required stability despite the fan’s 15mm “thin profile.” Remember, Noctua guarantees their products out to six years and to make a thin fan last that long took some work. They also never made a fan this thin. As our press contact commented, “All of the new models are new form factors for us.” So let’s have a look at this, the newest entry into the slim fan derby:

Introducing the Noctua NF-A12x15

Noctua says, “the NF-A12x15 is a highly optimized, premium quality quiet fan in size 120x15mm.” They go on a bit on their website but I wanted more details for you, the reader. So I asked where they think people will use this fan. What my contact said was we wanted to put the NF-A12x15:

“Basically everywhere a 25mm deep 120mm wouldn’t fit or would cause compatibility problems. One of the key examples would be low-profile down-draft CPU coolers like our own NH-L12, which will be updated with this fan later this year:

There are a lot of similar coolers from other manufacturers which also come with slim 120mm fans, so we expect that users who seek to replace these will also find the NF-A12x15 attractive. With some tower coolers, replacing a front-mounted 120x25mm fan with a 120x15mm one can help to improve RAM clearance.

With watercooling radiators, users sometimes have the issue that if they install them in the top or front of their cases with 120x25mm fans, either the radiator or fan will overhang the motherboard and possibly block some components. Using 120×15 can help here as well.

Similarly, clearance can also be increased in case fan applications or many other situations where you want to put a larger diameter, quiet fan but cannot fit 25mm thickness (think of adding a fan on a PCIe card, etc.).

Last but not least, we expect some demand from our non-PC industrial clients as well. There are a lot of applications where saving some space in order to build slimmer, more compact devices can be attractive.”

Features
(from the product page):

• Metal-reinforced motor hub. With many larger-diameter slim fan designs, the shorter axis and bearing lead to a reduced running stability and lifespan. The NF-A12x15 uses a metal-reinforced motor hub, a measure typically found in high-speed industrial fans, in order to guarantee Noctua’s signature stability and longevity.
• Flow Acceleration Channels. The NF-A12x15 impeller features suction side Flow Acceleration Channels. By speeding up the airflow at the crucial outer blade regions, this measure reduces suction side flow separation and thus leads to better efficiency and lower vortex noise.
• Noctua’s AAO frame (including Stepped Inlet Design, Inner Surface Microstructures and integrated anti-vibration pads at the corners).
• Low-Noise Adapter [PWM and FLX fans] and Ultra-Low-Noise Adapter [FLX fan] to reduce the speeds of the fans.
• SSO2 bearing, where the rear magnet is placed closer to the axis to provide even better stabilisation, precision and durability.
• For the PWM fan, NE-FD1 IC to produce silent PWM fan control. It suppresses PWM switching noises and thus makes the fan quieter at low speeds.
• Extensive cabling options. The fan’s short 20cm primary cable minimizes cable clutter in typical applications while the supplied 30cm extension provides extended reach when necessary. Both cables are fully sleeved. With the PWM version a 4-pin y-cable allows the connection of a second fan to the same PWM fan header for automatic control. With the FLX version the 3:4 pin adapter allows the connection of the fan directly to the power supply.

Noctua also advertises its six-year warranty. From personal experience and the testimony of a number of forum participants we can say that they have world-class customer service.

Specifications

* -one can see the conversion factors in the link above.

Unboxing

First we have a look at the boxes these fans come in. The front has the marketing points along with an embossed medallion that tells you that this is a 15 mm fan. The back repeats the marketing points as text in eight languages. You can find all of the NF-A12x15 specifications there. The front covers of the boxes open out to show you diagrams of their aerodynamic features, as well as giving you a window to see part of the fan itself.

Inside we have the fan and its accessories snuggled in a recyclable plastic case. Here the case is laid on top of its cover – the same cover that we saw on the box in the second picture above, providing a window to glimpse the NF-A12x15.

The NF-A12x15 FLX comes with a number of 3-pin accessories. Here we see, lying on an open copy of the Installation Manual, an NF-A12x15 FLX, an extension cable, a package of four standard fan screws, a Molex to 3-pin adapter, four double-ended soft silicon mounts designed to attenuate any stray vibrations, an LNA (a Low Noise Adapter, RC-10) and a ULNA (an Ultra Low Noise Adapter, RC-13) — you can’t tell which is which, but I have access to the original 3968×2232-pixel picture I took, and can read the labels. One thing about the four double-ended soft silicon mounts: you can trim off the ends if you don’t use them, leaving your case looking nice from the outside.

The NF-A12x15 PWM comes with various 4-pin accessories. Here you can see a four-pin Y-cable. It has the RPM-reporting line missing from one limb. This is the preferred construction since it sends a single RPM signal, thus refraining from confusing the motherboard. Next is a 4-Pin extension cable, a package of four standard fan screws, four double-ended soft silicon mounts, the fan in its shelter and a 4-Pin LNA (RC-7). Nice set. It all sits on an installation manual which is available online.

Outside the sheltering case, a pair of NF-A12x15 PWM fans stand up for your inspection. These are solid fans. You can feel their solidity when you take them out and handle them.

The next image shows the edge of the NF-A12x15 FLX is really only 15 mm thick. The edges are slotted. We have seen this before in thin fans, so the rib is there to improve stability. According to Noctua, “The slots on the outside of the frame are to make it more rigid and to make sure it doesn’t warp in the cool-off phase after injection molding.” So now we’re into manufacturing technology.

A closeup of the fan shows the various features of the AAO Frame – the vibration-absorbing corners, the stepped inlets and the inner surface micro-structures. You will also notice the small distance from the end of the blade to the inner surface of the frame. Having such close tolerances requires strict attention to quality control. Most fans leave a lot more room for manufacturing variation. Finally, notice the shape of the hub – that of a short cylinder, or a built-up pancake. That is the bearing. As my Noctua contact says, “The metal reinforcements of the NF-A12x15 don’t concern the motor as such, it’s just the impeller hub that’s reinforced. You’re right that the [other OEM] uses a similar design, but so do hundreds of other high-speed fans from various manufacturers.” Further, he noted, “You need to get the tolerances down if you want to get good performance in such a dense form factor. This is one of the reasons why we went for the metal reinforced hub because it helps to keep things nice and balanced even with such small tolerances.”

Noctua does not claim any special blade angle. However, I inspected several fans for blade angle. The NF-A12x15 seemed to have a similar blade angle to the NF-F12, the San Ace and the Gentle Typhoon, all seen below. They were distinctly shallower than the NF-S12A or the Slip Stream. This shallow blade angle is similar to a low gear on your bicycle or car, with the steeper blade angle being more like a high gear: those fans push air faster but have a relatively lower static pressure. However, I am still thinking about how to measure blade angle, and I’d welcome your thoughts in the comment section.

A view of the backside of the frame comes next. This side of the frame has a smooth exhaust expansion – no stepped slope here. Again you can see the inner surface micro-structures and the vibration-absorbing corners, this time with the whole shape in view. The impeller’s hub is 10 mm thick. At the hub the frame measures 4 mm thick, leaving 1 mm between the impeller and the hub, again showing good quality control. There are five struts connecting the hub to the frame, more than the normal three to four struts. This will aid in providing stability in a fan that is only 15 mm thick. Noctua’s spokesman said, “The five struts are for rigidity as well. To make it stiff enough with 4, the struts would have to me much thicker, so the overall impact on airflow would have been higher than with the 5 strut design we ended up going for.”

Setup for Testing

The fans were placed in a test stand, where their free air RPM was observed and their noise was assessed. The standard proxy for what you can hear is the Sound Pressure Level (SPL), measured in decibels and given a type A weighting (dBA). A silent room is about 30 dBA.

The ambient noise for this set of testing is 31 dBA. To measure noise levels that were softer, the Sound Pressure Level (SPL) was measured 10 cm from each fan. SPL was adjusted to 1 meter by subtracting 20 dB. The sound pressure meter is a Tenma 72-942. This fan tester has a microphone which is not accurate under 30 dBA. This is the limit of all but the most expensive SPL meters. At low levels sound measurement by extrapolation is not accurate, so that sound measurements are approximate.

The airflow was assessed using a standard measure, cubic feet per minute, or CFM. The air entered a sealed 8″x8″x8″ box (200+ mm on a side) where it was allowed to mix. The air left the box through an exhaust port, where it was measured with the vane head of an Extech AN100 anemometer, averaging 10 readings per fan setting. The fans were tested in an unobstructed state, with a metal mesh dust, on a 16 frame-per-inch radiator as a proxy for heatsinks and on a 30 FPI rad.

Results of Testing

There was little difference between free air and air impeded by a dust filter. As far as the NF-A12x15, the dust filter was hardly there. It turns out that this was no surprise to the folks at Noctua: “With all of the recent A-series models, we aim to have a very stable P/Q curve, so you’re right that you should see a lower drop in airflow when working against back pressure.” There being little difference between the NF-A12x15 FLX and the PWM without a LNA, the results were pooled. On the other hand, the results diverged between the PWM and FLX fans with LNA, so the averages were reported separately. All in all, you can see that the strong suit of the Noctua NF-A12x15 is quiet running.

In all three charts, fans with asterisks are slim fans.

With the 16 FPI rad results, there was a little more separation between the obstructed vs free-path results, but they stand out from their immediate neighbors as showing dips, or reduced unobstructed airflow. This is not a bad thing, though. It shows that compared to their neighbors they have pretty good static pressure. If we put the chart in order of unobstructed airflow, these fans would show their high flow through the 16FPI rad. I put in the NF-A12x15 FLX with UNLA because it can put air through a 16 FPI heatsink. You would use it in a heatsink only if you wanted a dead-silent rig. Since you might be looking to do just that, the NF-A12x15 FLX with UNLA was included here. The results of the PWM and FLX fans were very close so they were pooled for the airflow without and with the LNA.

Again the results of the PWM and non-PWM of the NF-A12x15 fans were very close so they were pooled for the airflow with and without the LNA. Again the fan with its ULNA was shown here because you might want a dead-silent rig.

Finally, we come to the issue of PWM control. Now, where there is a functional speed-reducing adapter we would expect the speed of the fan to be reduced at low PWM %. However, at the low end of the PWM of the Noctua NF-A12x15 PWM we get little reduction of speed, while as the PWM duty approaches and reaches 100% the speed diverges. This is exactly the way you would like a PWM fan to behave. RPM vs. PWM is graphically represented in the following chart:

The one thing that we can’t measure is the nature of the sound. The NF-A12x15 is like other fans from Noctua: it does not sound as loud as it measures. The SPL meter measures the sound pressure where it is sited. But sound pressure is not what you hear. You hear noise, and you can barely hear the sound the blades make as they whirl in the air. This is a quiet fan.

Pricing and Availability

Here is the MSRP for the Noctua NF-A12x15

• NF-A12x15 PWM: EUR 19.90 / USD 19.90
• NF-A12x15 FLX: EUR 19.90 / USD 19.90

As of this writing the NF-A12x15 is not available on Amazon or Newegg.

Conclusions on the Noctua NF-A12x15

Static pressure readings are nice to have, but all they really do is suggest how a fan might perform when blowing through restrictive environments. What you really want to know is how well will my fan push air through my cooler (in this case, it might be a rad)? When you take out the sleeve bearing fans what is closest to this fan is the $30 Noctua NF-A14 iPPC-3000 24V. And that is comparing the NF-A12x15 to 25mm thick fans. But this is a slim fan, and the pickings for those is, well, slim. In other words, you lose nothing if you go with this fan.

The Noctua NF-A12x15 is a fine fan, never mind that it is also a slim fan. They used airflow-enhancing features, close tolerances and a good rigid frame so that it would not warp – supporting those close tolerances. Noctua has gone all-out to make this a great fan.

They have also included a number of accessories so there is little or nothing left to buy. By including a LNA, they are in essence giving you a second fan. And the FLX having a UNLA, it’s like getting a third fan. When you look at the price, you are getting a great deal in a slim fan.

Overall, Noctua has built the NF-A12x15 as a slim fan to fit in tight places where a normal fan would not go. Better, they built a slim fan that would lose nothing in comparing it to normal thickness fans. Last but certainly not least, it’s a quiet fan, quieter than its competitors.

NF-A12x15 Pros

• Slim, only 15 mm thick
• Very quiet
• Surpasses surprising obstacles for such a slim fan
• Solid construction
• Many useful high-quality accessories included
• Anti-vibration rubber corner pads built in
• Both versions of the fan come with an LNA
• The FLX has an ULNA
• Comes with an installation manual that is also online
• Price is reasonable

NF-A12x15 Cons

• None

Click the stamp for an explanation of what this means.

Ed Hume (ehume)