360° View - Noctua NH-L9x65 Heatsink Information on Frostytech's test methodology is available here.
The NH-L9x65 heatsink stands 64mm tall and is equipped with a 92x92x15mm NF-A9x14 PWM fan that rotates at 2500-1800RPM. Power is supplied by a standard 4-pin mobo header. Each nickel plated aluminum fin measures 0.4m thick and is spaced ~1.5mm apart. The four 6mm diameter heatpipes are spaced roughly 13mm on center. With the fan removed, we can see the spring tensioned mounting screws from the top.
The bottom of the cooling fins are elevated 16mm above the CPU IHS. The copper heat spreader measures 2-5mm thick and is soldered to each of the four 6mm diameter copper heatpipes. The heatpipes are also soldered to the aluminum fins, rather than being swaged in position. The 15mm thick fan is held in place with zero-profile wire fan clips. Removing the fan is easy.
The base of the Noctua NH-L9x65 heatsink is a machined block of copper that has also been nickel plated to prevent long term oxidation. All four copper heatpipes are soldered to the center of this baseplate. The base has a machined surface finish and measures 38x40mm.

Base Finish and Flatness

Flipping a heatsink over to inspect the business end is often a simple indicator of overall cooler quality. More practically speaking, a heatsink is in many ways only as effective as the contact it makes with the processor - the flatter and smoother the better. Base finish is one of the criteria that Frostytech measure in the course of evaluating heatsinks, and it involves two distinct aspects. Surface Finish is the first; this is calculated with the aid of Surface Roughness Comparator that has a cross section of common machine surface finishes and their numerical surface roughness equivalents in microinches. The second is Surface Flatness. This is tested with an engineer's straight edge or proven flat surface, in two axes.

The Noctua NH-L9x65 heatsink uses a nickel-plated copper base plate which is machined (turned) very smooth, surface roughness is at or better than ~8 microinches. The base is very slightly convex in both axes.

The curious thing is, either Noctua turned the base to be slightly convex on purpose (ie. so it would make strong contact at the center of the CPU IHS if too much thermal compound was applied) or the lathe wasn't set up precisely, or the soldering process accentuated stresses in the punched copper slug and caused it to warp as the heatsink passed through the soldering oven... either way, Frostytech would have preferred a flatter base plate as every CPU integrated heat spreader I've measured at has generally been pretty damn flat.

Sound level measurements are coming up next on Frostytech...