Noctua NF-A4x10 FLX 40mm and Noiseblocker XM-2 fan review

As I’ve posted not long ago, I’ve bought a new platform based on X99 chipset attached to ASUS Sabertooth X99 motherboard. And this motherboard arrived with special fan that you mount on a VRM segment of the motherboard for additional VRM cooling. Well, the stock fan is PWM and mounted on a special fan header which even when set at lowest speed makes it quite noisy and you can’t force the fan curve any lower. Too noisy considering the rest of the fans are almost dead silent. So, I’ve tossed it out and looked for alternatives…

After lengthy digging after 40mm fans (they really aren’t easy to find), there were few options at 10mm thickness that caught my attention. The Noiseblocker XM-2 that I already had, but is somewhat weak on the air pressure aspect, Gelid 40mm Silent Fan or Noctua NF-A4x10 FLX. I wanted the Noiseblocker BlackSilentPro 40mm but it only comes in 20mm thickness so that fell off my selection list.

I’ve checked bunch of resources and decided to go with Noctua. HalTech reviewed it and gave it very positive review on Youtube. Noctua is also known for high quality products (apart from absolutely terrible skin+diarrhea color scheme) and it has air pressure higher than some larger fans.

I was really enthusiastic about it…


Till I actually got the fan. Yeah, that color scheme… but fine, it sort of fits to desert beige and grey found on Sabertooth X99. Presentation is amazing. High quality box with preview window secured with a Velcro “lock”, bunch of really high quality accessories like amazingly well sleeved cables, anti-vibration holders, slowdown resistor etc. Really top notch, but then again, for almost 15€, I wasn’t expecting any less.

There was immediately a problem with fitting of this fan inside the cooling slot on Sabertooth X99. This damn fan is not standard 40mm size, I had to grind away the pointy parts on the corners in order to even be able to fit this darn thing in the fan slot. After I’ve done that, second problem appeared…

Connected everything, fired up UEFI BIOS and tested this bad boy. And guess what, this fan is TERRIBLE. Considering it’s loaded with anti-vibration, anti-noise, anti-everything with superduper SSO2 150 trillion hours hydro bearings with SCD2 drive and the review from HalTech stating it’s dead silent, this fan is anything but silent. Sure, it’s a 4500 RPM fan, but even when you slow it down, it doesn’t actually get any more silent. Connected the L.N.A. resistor in between to slow it down to 3700 RPM and further slow it down using UEFI BIOS controls and the damn thing was still buzzing and hissing like crazy. There is a third problem with it, if you partially block/obstruct its air intake and that’s exactly what happens since rear exhaust fan partially covers it, Noctua starts making really annoying whining noise.

It’s the noise frequency which is so irritating it makes you think it has 10.000 mosquitoes electrocuted inside the fan and that makes it spin. Even when absolutely slowed down it makes this god damn annoying buzzing noise that was driving me insane.

Yes, the air pressure is phenomenal for such tiny fan and you can properly fell it, but there is no way in hell I’m gonna listen to this buzzing crap. Sorry Noctua, but you failed badly here.

Pros and cons for Noctua NF-A4x10 FLX:

+ high quality packaging and presentation
+ attention for details (quality cable and resistor sleeving)
+ amazing air pressure of 1.21 mmH2O @ 3700 RPM
– motor is emitting super annoying buzzing noise across entire RPM range
– partially restricting air intake creates horrible whining noise
– fan frame is not perfect 40mm standard (holes are, the frame isn’t)
– a bit expensive for a tiny 40mm fan (considering the noise problems)

Alternative? Yeah, I’ve gone back to my all time favorite fan maker, Noiseblocker, more specifically to XM-2 fans that I had for ages but somehow decided to neglect it and give Noctua a try…


I don’t know what kind of witchcraft Noiseblocker is doing, but the XM-2’s that I have are old generation with sleeve bearing and they are dead quiet. At freaking 3800 RPM! New XM-2’s that you can buy now even come with Noiseblocker’s higher grade NB NanoSLI bearings. If their sleeve bearing is this quiet, how freaking quiet is the new generation of XM-2’s then!?

Anyway, XM-2 fits in the Sabertooth X99 directly without any modifications, is absolutely quiet at 3800 RPM meaning I’m running it full speed at all times and restricting its air intake doesn’t really change its acoustic properties. Air pressure is slightly lower as well as air flow, but if I have to trade that for silence, I’d do it any time. And I have.

Pros and cons for Noiseblocker XM-2:

+ attention for details (maybe not Noctua level, but still very good)
+ standard 40mm size
+ amazingly silent at full 3800 RPM
+ pretty color scheme
+ reasonably priced
– slightly lower air pressure and airflow compared to Noctua


If you don’t have to look at the ugly fan and you just need a high performance 40mm fan to cool system chipset or VRM, Noctua is certainly an amazing option. But if you want a high(er) performance 40mm fan that is also really super quiet at 3800 RPM, go with Noiseblocker XM-2. I’ll one day have to check out that Gelid, but for now, XM-2 is still my favorite fan. It’s just a better balanced product compared to Noctua which is amazing in some aspects, but also absolutely terrible in others.

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