When reviewing silent cooling solutions we are often forced to recognize that silent cooling doesn't always translate into good overclocking performance yet, there are a few notable exceptions. Thermal performance comes from a variety of factors like the size of the radiators, number of heatpipes and cooling fan(s). The position of the heatpipes is also key in making sure heat is evenly distributed across the radiator and takes advantage of the primary airflow across the fins. As our benchmarks showed the NH-D15 is extremely efficient under stock loading conditions.
Much like the D14, the newer D15 is an extremely large for a heatsink and needs room to breathe. Due to its size some concessions were built in like the large relief cuts in the bottom of the towers for tall memory modules. This is a welcome addition but does remove a good amount of surface area from the cooling equation.
The NH-D15 comes with two NF-A15 150mm fans with one designed to fit between the cooling towers. The gap between them is for noise control so you cannot guarantee that air will be pulled thru one and pushed out the other. To help increase performance you can use the second NF-A15 provided your memory modules and case allow it. In some situations you may be limited by space so a smaller NF-F12 can be used, assuming you have one lying around.
As always the installation hardware is extremely good and features a universal mounting system that is easy to install and works on almost every Noctua cooler. We tested on the X79 platform which uses the 4mm threaded rises. For those using Z87 or Z97 the installation process is identical after you have built up the base using the included backplate and spacers.
Overclocking performance was really good using the NH-D15. The 4.6Ghz overclock we use for testing is usually enough to overstress many heatsinks to the point where the C/W numbers will begin to change. With the NH-D15 we noticed that the number was identical between standard and overclocked tests which are a good indication for any heatsink. The temperature variance also remained the same between the single and dual fan tests which can be seen on the temperature charts. Overall the NH-D15 might be large but satisfies both the silent cooling and performance roles quite nicely.
Noctua Mounting System
Two NF-A15 Fans Included
Six Heatpipe Configuration
Memory Cutouts for Clearance
Surface area and airflow loss due to memory cutouts