360° View - Noctua NH-D9L Heatsink Information on Frostytech's test methodology is available here.
The NH-D9L heatsink stands 114mm tall and is fitted with a 92x92x25mm NF-A9 PWM fan that rotates at 2000RPM. Power is supplied by a standard 4-pin mobo header. A second fan can be attached, increasing the NH-D9L's length to 122mm. The nickel plated aluminum fins measure 0.4m thick and are spaced 1.75mm apart. Heatpipes are spaced roughly 18mm on center.
The Noctua NH-D9L utilizes two 67mm tall stacks of nickel plated aluminum fins soldered to four 6mm diameter copper heat pipes. The lowest cooling fin is elevated 35mm for motherboard clearance. The copper heat spreader measures 2-5mm thick. Wire fan clips have low-profile thumb tabs which make fan removal easy, but don't stick out so far as to get in the way of things like PCIe videocards.
The base of the Noctua NH-D9L heatsink is made from a punched and machined block of copper which is nickel plated. All four copper heatpipes are soldered to the center of this baseplate. The base has a machined surface finish and measures 38x40mm. Looking at the top of the heatsink we can see that each aluminum fin is 95 x 33mm in size and features a small recess to create natural plenums fore and aft of the fan. Fans can be mounted on the front or rear sides.

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-D9L heatsink uses a nickel-plated copper base plate which is machined very smooth, surface roughness is at or better than ~8 microinches. The base is very slightly concave in the axis parallel to the heatpipes, very slightly convex in the opposite direction.

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