At first glance, the NH-C14 might look very similar to its predecessor, the NH-C12P. Closer inspection, however, reveals several subtle changes.
Noctua has widened and lengthened the fin array slightly. Also, the large gaps on both sides which allowed access to the mounting screws on the NH-C12P have been replaced on the NH-C14 by much smaller gaps which are just enough to allow access with a long screwdriver. As we mentioned earlier, part of the fin array no longer extends down to the heatsink base on the NH-C14.
On balance, the surface area of the NH-C14 should be quite similar to that of the NH-C12P.
Another change is the spacing of the six heatpipes. On the NH-C14, the innermost two pairs of heatpipes are much closer to the center. Noctua might have made this change because the 140mm fan's airflow does not cover the extreme corners of the fin array.
The shape of the fins has also changed, with the center portion sloping inwards slightly. Presumably this helps to mitigate the effect of the dead spot underneath the fan motor.
Rubber spacers have been pre-installed on both the top and bottom of the fin array. If you look carefully, you can spot the curved support strut in the middle which extends across approximately half of the fin array. This helps to support the weight of the heatsink and perhaps also prevent excessive oscillation. During testing, we did not notice any vibration issues with the NH-C14.
The copper base of the NH-C14 is very smooth and flat. According to Noctua, the heatpipes are soldered to the heatsink base. Even though the NH-C14 uses only two screws for mounting, we found mounting pressure to be sufficient and evenly distributed.
In case you're wondering, the base and heatpipes are nickel plated to match the color of the fin array and protect against corrosion.