The copper heatpipes are set in grooves in the cooler base and then go nonlinearly through the heatsink array:

These two things should improve the cooling efficiency. In the first case, heatpipes have bigger contact area with the cooler base; and in the second case the heat should be distributed more evenly over the heatsink. Non-linear heatpipes positioning also creates additional airflow resistance.

The copper plate in the base of the cooler is barely finished at all. You can not just see, but also clearly feel the machine marks on the base:

Moreover, the base of the cooler sample we received in our lab turned out bent inwards. As you can see, only its sides actually touched the CPU heat-spreader or the test glass surface:

After researching a few forum threads, we discovered that we were not the only ones who experienced problems with uneven cooler base of Noctua NH-U9B. Well, looks like Thermalright is not the only company after all that has uneven cooler bases :)

With a bent base like that the cooler couldn’t work efficiently enough even in the nominal CPU mode. So, I had to use a few types of sand paper to shave the dents off until I managed to obtain a more or less acceptable thermal compound imprint, efficient enough heat dissipation and the opportunity to overclock my test CPU even with Noctua NH-U9B:

I didn’t polish the base surface. To be fair, I have to say that out of four Noctua cooler we have tested so far in our lbs, this is the first one with an uneven base like that.

Unlike its predecessor, Noctua NH-U9B is equipped with a new NF-B9-1600 fan measuring 92 x 92 x 25mm that is actually a smaller modification of NF-P12, we have already discussed in our roundup:

According to the official specifications, the fan rotation speed makes ~1600RPM (±10%) creating 64.3m³/min airflow and generating 17.6dBA of noise. If you use the bundled adapters with built-in resistors, you will be able to lower the fan rotation speed to ~1300RPM and ~1000RPM. The airflow and noise level will also drop down respectively.