Closer Look: Noctua NH-U14S
This is the NH-U14S, which employs a 140mm NF-A15 PWM fan and six copper heatpipes in a “U” shaped arrangement through a standard tower heatsink configuration. There’s a lot of details to cover, so let’s get started.
Of course, the premier feature is the included NF-A15 140mm PWM fan. Contained within a 150mm-wide frame and using 120mm mount spacing, this fan includes an entire list of acronyms. They’re all here: the SSO2 bearing, AAO Frame, custom PWM IC with SCD, a L.N.A and CNC milled brass bearing shell. So, moving on…
…Scared you for a bit eh? There’s a lot of letters in there, and it’s actually worth taking a little time to explain some of the technologies that Noctua has included with this cooler.
First, the SSO2 bearing. SSO stands for self-stabilizing oil-pressure bearing. This bearing type combines an oil-based bearing that is stabilized by an additional magnet placed closer to the axis of the rotor. Not relying solely on the CNC milled brass bearing shell for stabilizing something that revolves 1,200 times per minute probably helps Noctua achieve a 150,000 hour MTBF for the fan, and that gets backed by a six year warranty – one of the longest I’ve seen in a rapidly evolving market like enthusiast hardware.
AAO stands for Advanced Acoustic Optimization, and describes the features Noctua added to the frame to reduce vibration and increase efficiency with respect to noise. To do this, they’ve integrated (silicone, I’m assuming) anti-vibration pads on all corners (the NH-U14S comes with an additional, thicker set of pads that can be swapped out on a second fan in a pull configuration) and a series of “steps” or ridges along the intake rim to rough up the incoming airflow (the smooth intake flow of air will get mixed up anyway by the blades – doing so a bit beforehand will reduce noise when that occurs). This Stepped Inlet Design has the side effect of increasing performance respective to a smooth curve when placed against an intake filter or other restriction. Noctua doesn’t stop there with their acoustic optimization though, as the inner surface of the frame is filled with “microstructures” that – well, perform science (It helps reduce the noise of the blades as they pass by while improving airflow – I’m assuming the effect might be similar to the use of dimples on a golf ball).
And that’s just the frame. The fan blades themselves aren’t safe from Noctua’s engineering, as the intake side (or “suction side” as Noctua calls it) of the blades feature Flow Acceleration Channels. These are additional angled surfaces that serve to do precisely what they say: accelerate the flow of air along the outer edge of the blade. The tips are moving through the air faster than the center of the blades, but the airflow (before it hits the impeller) is probably all moving at the same speed (and a low speed at that). When you have a fast blade hitting a slow mass of air, the tendency is for the air to “spill” off the end of the blades and form vortices. A vortex generally makes more noise than a smooth flow of air, so increasing the speed of the air along the perimeter of the fan blades helps cut down on this noise (and serves up a more efficient flow of air too).
I’m sure there’s even more science to delve into, but hopefully it’s clear there is a reason Noctua has developed a reputation for (what I like to call) “knowing what they’re doing.” Perhaps to drive the point home, Noctua sent an additional NF-A15 PWM fan to test a push/pull configuration. This fan is a twin to the included 140mm fan and attaches through the use of an extra metal clip in the “Accessories” box of the NH-U14S. Again, the fan frame itself is 150mm in diameter, but two sides are flattened to make sure the NF-A15 can fit in any place where a 140mm height is the limit. There’s a healthy amount of accessories included as well – along with all of the aforementioned Noctua technologies, each NF-A15 fan includes soft mounting posts, normal screws, a low noise adapter and a PWM splitter/extension cable.
The premium experience starts with the packaging, and Noctua neatly separates the accessories and mounting hardware in clearly labeled compartments (this was an unexpected luxury – it was nice to just “pick your socket,” no sorting through a bag of accessories to find the relevant hardware). The heatsink and fan assembly is located underneath these three boxes, and is safely packed in a similar cardboard compartment. An extended screwdriver is a nice addition for reaching past the heatsink fins to secure the cooler to the mounting bracket, and Noctua includes a tube of their NT-H1 thermal compound and enough hardware to mount an additional fan.