Noctua NH-D15S Review (Page 2 Of 4) - APH Networks

Page 2 - Physical Look - Hardware; Installation

A view from the top three-quarter view of the heatsink. Unless you look very close, the Noctua NH-D15S is practically identical to the original NH-D15 from this angle in our photo above. If you are familiar with the NH-D15, it was based on same form factor as the Noctua NH-D14, but the radiator design was, in all practicality, two modified NH-U14S stuck together. The only thing that has changed is the fin stack is offset slightly with relation to the base, so it is biased towards the upper edge of the motherboard to prevent interference with the first expansion slot. We will go over this in more detail in just a moment.

As far as engineering and implementation goes, fans can be mounted on using two clips each. Only one NH-A15 PWM fans are included out of the box, and it is pre-installed for packaging reasons (You will need to take off the fan for installation anyway). A secondary fan can be purchased separately if you wish to execute a dual fan configuration. These wire clips are easy to attach and remove in a uniform fashion. Rubber strips on the heatsink are superseded by integrated rubber dampeners on the included NF-A15 PWM, used to reduce mechanical noise emissions during operation.

Noctua’s NH-D15S takes a hybrid approach in the heatsink fin leading edges compared to their previous designs, which is something we have first seen in the NH-U14S, NH-U12S, and of course, the NH-D15. This is characterized by its low angle V-shaped slope towards the center, sort of like the NH-U12P, but includes bits of zigzag edges in the original NH-D14. By doing this, the company attempts to maximize its ability to permit airflow between the fins with minimal resistance and turbulence noise -- all with a negligible decrease in heatsink surface area. There are thirty eight full sized aluminum plates on the radiator, and seven smaller ones near the bottom to take advantage of the bigger fan. The spacing is reasonably spaced, designed to be a little less dense compared to the NH-U14S. From my calculations, the total surface area of all the cooling fins combined is approximately 1.2 square meters, which remains unchanged from the non-S variant.

The Noctua logo and branding is engraved on the top fin horizontally. The company specifies the NH-D15S at 980g with no fans installed. With one stock fan attached, it will tip the scale at 1150g according to the manufacturer. I cannot call this heatsink lightweight by any objective measure, but considering the size, keeping it at just under a kilogram is a good number. A heatsink that is too heavy may stress the motherboard physically, but its effect can be somewhat mitigated with a well-designed installation bracket. Generally speaking, the material composition of the heatsink is crucial to this property -- we will take a closer look at the construction of the NH-D15S in just a short moment.

The Noctua NF-A15 PWM is very easy to dismount from the heatsink itself. It clips on the outer side of the fan, with a two stage clipping ledge for an easy yet secure installation. From the angle denoted by our photo above, we can see the clips are mounted over a two stage recessed ledge integrated into the heatsink fin design. Wire clips are attached directly to the fan instead of plastic clips. Because the wire clip retention length is reduced to a balanced level rather than spanning the entire height of the heatsink as we have seen in old Noctua products, attachment stability is not compromised -- but the revised advantage is obvious. It is even easier to remove the fans with tabs in the wire, and the clips can also be removed uniformly. This also allows more flexibility in fan-heatsink location alignment for the user.

Normally, you will not need to replace the otherwise excellent NF-A15 on the Noctua NH-D15S but it still needs to be removed during installation. The NF-A15 is an improved version of the NF-P14. From what I can see on Noctua’s website, it looks like the NF-A15 is a combination of the NF-F12 PWM and NF-P12 PWM, where both has been reviewed here at APH Networks before. Generally speaking, you probably will not find a better home elsewhere in your computer, nor will you find a better fan in the market today for this purpose, so I highly recommend you to keep it on your heatsink -- until Noctua comes up with a NF-F15 or something, of course.

The Noctua NH-D15S is a mega sized heatsink. Six continuous U-shaped heatpipes lead away from the CPU contact base in two opposing directions for twelve effective heatpipes. Those heatpipes then go through two independent radiators, one on each side, to dissipate the heat into the surrounding environment. Theoretically, the heatpipes are supposed to efficiently lead the heat away from its source due to the low heat of vaporization, or phase change energy, of the fluid inside. The heatpipes are aligned in a linear but asymmetrical manner to evenly distribute the heat in the radiating fins, as the NH-D15S is really two reduced weight NH-U14S heatsinks stuck together. The Noctua NH-D15S does come at the cost of physical size; its height of 160mm and width at 150mm is pretty standard -- but its length is the one that makes it literally stand out. In standard configuration, with one fan mounted in the middle, it already comes in at 135mm depth. Add an extra fan to the front, and this figure jumps to 161mm. That said, with 1.2 square meters of surface area, combined Noctua's excellent NF-A15 PWM fan that is specifically designed for heatsinks with a high amount of static pressure, you are definitely going to get some serious cooling performance and low noise levels -- something we will investigate on the next page.

There is a clearance room of about 6.5cm between the heatsink contact base and the bottom of the upper fin array. This is the area where the NH-D15S will extend over your RAM slots, and that is quite a bit of space. In fact, you can probably get some higher profile memory to slip under. However, if you choose to install an optional second NF-A15 PWM fan in front of the first radiator, it will completely override any clearance room provided in this area. In fact, you will need a wide case with lots of clearance room between the motherboard and the left side panel, like the Fractal Design Define R5. The NF-A15 will need to be mounted high on the heatsink, as it will interfere with any RAM regardless of profile. Unless you mount your NH-D15S in a non-standard orientation, this will definitely be an issue.

A shot of the bottom of the Noctua NH-D15S CPU heatsink. The photo above shows the configuration of the heatpipes more clearly in relation to the base leading into the fin array. As mentioned earlier, the fin stack is offset slightly with relation to the base, so it is biased towards the upper edge of the motherboard to prevent interference with the first expansion slot. My only complaint is the Noctua logo at the top of the heatsink will actually be upside down if you install the NH-D15S correctly, which does not make sense to me. Conversely, if you install the NH-D15S with the Noctua logo right side up, the fin array will be biased downwards, causing additional interference with your expansion slots. This is purely a cosmetic issue, but for a company that has an excellent history of focusing on the details, I do not believe my complaint is out of hand.

Update: Noctua said the upside-down logo was an issue only with a small batch of initial production units. The ones that are currently shipping have the right orientation.

Like all Noctua heatsinks we have reviewed in the past, the NH-D15S is a copper and aluminum hybrid heatsink electroplated with nickel. The vital parts such as the base and heatpipes are built using copper for best heat transfer ability with a thermal conductivity of 401 W/mK. The heatsink fins utilize aluminum as its material due to its lightweight properties as juxtaposed to copper. This is to allow the construction of larger heatsinks without stressing too much on the motherboard due to weight. Aluminum has a thermal conductivity of 237 W/mK, which is not as optimal for heat transfer compared to copper, but it is much lighter.

While this is all quite interesting information, visually speaking, the NH-D15S from Noctua has none of the copper color with its copper heatpipes and base. According to the specifications, the Noctua NH-D15S is electroplated with nickel on top of its copper, which has a thermal conductivity of only 90.9 W/mK. Even though nickel has lower thermal conductivity than copper, which may limit heat transfer, the electroplated layer is very thin, and should not directly affect performance to a significant degree -- but it is likely related to the corrosion allowance factor. Nickel and nickel-base alloys generally have desirable properties that can withstand corrosive environments and high temperatures, which are especially beneficial for a heat dissipation device. The contact base in the Noctua NH-D15S has a generally clean and flat finish for optimal performance, as you can see in our photo above.

The reason why nickel has such a property is because of nickel's ductility and toughness all the way up to the melting point of 1455°c, measured at non-standard pressure. Nickel's face-centered cube crystal structure is virtually unaltered all the way up to that temperature. Nickel, like titanium, is highly resistant to corrosion, therefore corroded material will not build up on the surface in the long run. It is surely a good sign, because the NH-D15S will be less prone to losing its cooling performance over time, as compared to a corroded copper surface.

Additionally, all the joints are cleanly soldered at the base, as well as the fact that the heatpipes are soldered to the fins, so that it will not lose contact over time. Lower quality heatsinks offer high initial performance, but degrades over time as contact between metals decreases due to thermal expansion and contraption. Overall, the Noctua NH-D15S appears to be built very solidly. Reliability should also be excellent as I have seen with every Noctua heatsink I have used since 2007, which retains performance very well over time.

Installation proves to be very simple. Noctua packaged each set of installation accessories individually for excellent organization; along with the clear and concise setup poster, setup was a breeze. This is not to mention I have used the SecuFirm2 system with the NH-D14, NH-D15, NH-U12S, and NH-U14S before. Needless to say, by this time, I do not even need to read the poster to get everything going. As you can see in my photo above, Noctua's mounting system on the Intel platform utilizes a proprietary backplate supplied by Noctua that installs over the stock plate for optimal weight distribution. The inertia generated by such a large heatsink is really something that needs to be addressed accordingly, otherwise it may simply fall out, or otherwise cause excess stress on the motherboard. To install, simply align the openings on the supplied backplate with the screws of the motherboard's stock backplate, and flip the motherboard around.

The Noctua NH-D15S, like the NH-D15, uses the latest revision of the SecuFirm2 mounting system. Changes from the original include a backplate with new mechanics, as well as integrated bolts. Functionally, the revised mechanics does not change anything regarding its compatibility, but the integrated bolts make installation less of a pain in the butt. The part number for the backplate, NM-IBP2, has the text "Rev. 2" underneath it. What exactly are the changes from Rev. 1? Well, the plate now has a seam at the beginning of the extension of each leg, and the finish on the inner side has been modified. Other than that, everything else is one hundred percent identical, and you can definitely interchange parts between models without issues.

Two mounting bars are included for attaching the heatsink to the motherboard. First, put the plastic spacers onto each integrated bolt. The user then has the choice of either aligning the mounting bars according to the final desired orientation of the cooler, as the NH-D15S can be installed either horizontally or vertically. For the S version we are reviewing today, you are probably better off installing it with the fins oriented horizontally. Our photo above shows the alignment of the mounting bars for such installation. Tighten the screw caps over the bolts, and you are good to go.

Fastening the heatsink over the CPU socket proves to be a simple job. Remove the center fan to gain access to the spring loaded screw located on the NH-D15S heatsink itself. Align the heatsink with the screw threads on the mounting bars, and tighten the screws alternately until they stop. Overall, installation is straightforward, and Noctua's mounting system is very secure and distributes weight very well, even though the heatsink is quite big and heavy in nature.

Unlike many tower heatsinks I have used in the past, the NH-D15S in single fan configuration mode did not interfere with my RAM, thanks to the high clearance fins. The offset fin stack worked well in preventing interference with the first expansion slot as well, so to answer the question in the beginning of this review, yes, Noctua's strategy worked. Of course, you are going to have less space around the CPU socket for your hands to work with, so make sure you connect your EPS 8-pin connector and fan cable first. Also, if you add an optional second NF-A15, here is where you may start to have issues. As I have mentioned earlier, it will definitely interfere with your memory, no matter what profile it is. Therefore, you will need to mount the fan a little higher to accommodate the difference. This configuration may not be possible for some people, because some chassis simply are not wide enough to support so much space between the side panel and the motherboard. Therefore, I would recommend a 120mm NF-F12 as a secondary fan instead.

Page Index 1. Introduction, Packaging, Specifications 2. Physical Look - Hardware; Installation 3. Test Results 4. Conclusion