I’ve always been fascinated by liquid-cooling setups for PCs. When I started building my own computers about a decade ago, liquid cooling had an exotic mystique. It was the mark of the most dedicated enthusiast, a mad-scientist-y whirl of custom water blocks, home-brewed tubing setups, and radiators pressed into Frankensteinian service from wherever they could be found.

Those mad scientists are still out there, but liquid cooling has become much more egalitarian of late. There’s a dizzying array of closed-loop liquid coolers, or CLCs, available to the PC builder. CLCs do away with the complexity of fully custom loops in favor of plug-and-play designs.

That brings me to the cooler I’m looking at today, Cooler Master’s $130 Nepton 240M. The Neptons represent the high end of Cooler Master’s CLC lineup. These offerings include larger-diameter flexible tubing, higher-quality fans, and a more advanced water block design than the company’s less expensive Seidon CLCs. With a 240-mm radiator, the Nepton 240M should have enough thermal capacity to handle even the hottest-running of today’s processors. Let’s take a look at the goodies Cooler Master has packaged with the Nepton 240M, and then we’ll put it in the hot seat.

Overview

At first glance, it’s easy to dismiss CLCs as a “seen one, seen ’em all” deal, but that would be a mistake. While the general principles remain the same from one to the next—an integrated pump and water block unit circulates coolant through a sealed radiator loop—there’s still plenty of room for manufacturers to put their own spins on the concept.

Let’s start with a look at the pump and water block on the Nepton. According to Cooler Master, the water block in the Nepton series features “ultra-fine micro channel” technology, which makes for an internal surface area that’s four times larger than water blocks from “the competition.” While I can’t tear into the Nepton 240M to verify this claim, more surface area in the water block should make for better heat dissipation, so long as the ultra-fine fins don’t impede coolant flow.

The copper mating surface on the water block isn’t polished to a mirror sheen. Instead, it’s ever-so-slightly grooved, perhaps to ensure that thermal paste can be squished into contact with as much of the plate as possible.

The pump inside the Nepton 240M isn’t a run-of-the-mill unit, either. Cooler Master says it can move 120 liters of coolant per hour while producing only 11 dBA of noise. The company doesn’t say how it arrived at this impressive noise figure, but the cheaper Seidon 120V has a vaguer “less than 23 dBA” noise rating, so the Nepton pump should be noticeably quieter than its sibling. (In my experience, the Seidon’s pump is pretty coarse-sounding.) When the Nepton 240M is powered on, a white LED illuminates the Cooler Master logo on the pump, too. Fancy.

The business end of the Nepton 240M is its 240-mm radiator. This heat exchanger is joined to the pump by a pair of flexible, ribbed tubes. True to Cooler Master’s specs, these tubes have a noticeably larger diameter than those used on the Seidon 120V. The radiator is about as thick as the Seidon’s—just doubled in length. Out of the box, the radiator had zero bent fins, which I find reassuring from a quality-control standpoint.

There’s a fill port on the radiator, but it’s plastered with “warranty void if removed” stickers. (This is a sealed system, after all.) Should a problem arise with your Nepton 240M, Cooler Master backs up the Nepton line with a five-year warranty.

Left: the Silencio 120. Right: the Seidon 120V’s stock fan.

On the active-cooling front, two of Cooler Master’s new Silencio 120 fans ship with the Nepton 240M. In contrast to the seven-bladed fans packaged with the Seidon 120V, these 120-mm blowers each have five broad blades with much more aggressively swept tips. True to their name, the Silencios are rated to produce only 11 dBA of noise in operation. Cooler Master includes a rubber gasket that’s designed to sit between the fans and the radiator, hopefully dampening unwanted vibrations from these air movers.

The final element CLC buyers will likely consider is CPU socket compatibility. Cooler Master includes mounting hardware to secure the Nepton 240M to virtually every Intel and AMD socket that one might find in use today, from LGA775 and Socket AM2 to LGA2011 and Socket FM2+.

Overall, the Nepton 240M appears to have all of the right stuff for a high-end CLC. It comes at a price, though. Cooler Master’s MSRP for the Nepton 240M is $129.99, which is about $15 more expensive than the best 240mm CLCs from Corsair and other manufacturers. Let’s hope that its performance matches this lofty figure.

Next, I’m going to strap the Nepton 240M to a processor and see how logical and user-friendly the mounting system is.

Installation

For my testing, I mated the Nepton 240M to my version of TR’s Casewarmer, which is built around an AMD A10-7850K processor with a 95W thermal envelope. The 7850K is installed in a Socket FM2+ motherboard, the MSI A88XI AC.

While the Nepton 240M’s mounting hardware differs from socket to socket, the process starts with a universal backplate. The rest of the pieces for each specific socket type are mounted on top of this plate.

First, I clipped the appropriate quartet of bolts to the universal backplate before threading them through the mounting holes in the motherboard. I then secured the backplate to the motherboard using the four female-female nuts provided. This solution is much better thought-out than the Seidon 120V’s. That cooler’s mounting bracket is free to fall back out of the motherboard at this stage. The Nepton 240M’s intermediate nuts also provide a more solid foundation for the water block. The Seidon 120V’s pump can twist around on the processor if too much stress is placed on the coolant hoses, since there’s nothing directly securing the bracket to the motherboard.

Next, I secured the proper brackets for AMD sockets to the pump block with four screws. This process is a little more involved than it is with the Seidon 120V, whose mounting bracket simply slips over the top of the water block.

After applying the included thermal paste to the processor’s heat spreader, I screwed each of the four spring-loaded bolts into their complementary nuts, using the star pattern suggested by the manual to achieve an even clamping force.

As you can see above, the Nepton 240M is a very tight fit on the A88XI AC (and probably other mini-ITX motherboards, as well). The fittings for the pump clear the RAM by about half a millimeter. If you’re thinking about a Nepton for your mini-ITX build, be very careful about the RAM you choose. The Nepton’s pump might run into over-wide heatspreaders.

Finally, I mounted the system inside my testbed case, the Corsair Carbide Series Air 240. (Keep an eye out for my review of this case soon.) I set up the fans as intakes to ensure the CPU would be cooled by the freshest air possible.

I tried to mount the radiator using the rubber vibration-dampening gasket, but keeping the fan-gasket-radiator sandwich together during installation proved impossible. In the end, I set the gasket aside. Builders setting up the Nepton 240M with the fans on exhaust duty will probably have an easier time.

Let’s now fire up Prime95 and see how the Nepton handles the A10-7850K switching away beneath its water block.

Our testing methods

After a short breather, the Casewarmer is back in action. Here are its specs, for reference:

Processor AMD A10-7850K Motherboard MSI A88XI AC Memory 8GB AMD DDR3-1600 (2x 4GB DIMMs) Graphics card Zotac GeForce GTX 660 Ti AMP! Edition Storage Kingston HyperX 120GB SSD Power supply Cooler Master V550 OS Windows 8.1 Pro

A big thanks again to MSI, AMD, Zotac, and Kingston for contributing some of their excellent hardware for my use—and to Cooler Master for providing me with the V550 PSU and Seidon 120V.

As I’ve documented, the fan control situation on the MSI A88XI AC isn’t the best. Despite the limitations of the MSI firmware, I was able to create proper fan profiles for the Nepton 240M and Seidon 120V, which I used in each cooler’s respective test cycle.

To put the heat on these CLCs, I subjected each one to the following test cycle:

10 minutes idling at the Windows 8.1 desktop

20 minutes of the Prime95 CPU torture test

10 minutes idling at the Windows 8.1 desktop

Sensor data was logged using AIDA64 Engineer. Ambient temperature at the time of my tests was about 74°F (23.3°C).

The tests and methods we employ are publicly available and reproducible. If you have questions about our methods, join us on our forums to discuss them.

Cooling performance

Here are temperature results for each cooler, plotted over time. For comparison purposes, I also ran my test cycle with the Seidon 120V. I set up the Seidon in the same location as the Nepton, with the fan configured as an intake.

And here are some minimum and maximum temperatures from my test cycle:

I was expecting a slightly greater difference in performance between the two coolers, as the Nepton 240M has twice the surface area of the Seidon 120V. Even so, the Nepton kept the A10-7850K plenty cool, with temperature rising only 15°C from idle to load. What these charts don’t tell you is that the Nepton delivered these results with the fans at idle for the entire 40-minute testing period. Bonkers.

The Seidon, with its area disadvantage, did have to spin up its fan a bit in order to keep things cool. Despite that fact, and despite lacking the fancy pump and larger tubing of the Nepton, the Seidon didn’t fall far behind its bigger brother. The results might be different once overclocking enters the picture, but the A88XI AC won’t overclock APUs with a 95W TDP. A shame, since I would have liked to really push both of these coolers. I have a more overclocking-friendly motherboard heading my way, but it didn’t arrive in time for this review.

Noise levels

To gather data on the noise produced by these CLCs, I’m once again relying on the iOS app dB meter. Take the results with the appropriate grain of salt. Each measurement was made 6″ from the case.

I love it when a piece of hardware leaves me very little to say. The Nepton 240M is a good example. Look at these noise numbers:





That’s what happens when your CPU cooler doesn’t have to move its fans off idle to keep things cool. This is outstanding performance, and it’s actually a little unnverving. I’m so used to CPU fans whining away under Prime95 loads that I had to double-check the Casewarmer several times to make sure something was actually happening. The Seidon is pretty closely matched against the Nepton when both coolers are at idle, but the 240M wins by not having to stretch itself under load.

Subjectively, the Nepton is a better-sounding cooler than the Seidon 120V. There’s still a minor hum from the pump, but it’s less “chuggy” and slightly quieter, which makes it easier to ignore. The Nepton’s included Silencio 120 fans are also much more refined than the basic Cooler Master unit supplied with the Seidon. The Silencios have a smooth, broad-spectrum noise character, and they’re virtually inaudible at idle unless one’s ear is pressed against the front of the case.

I’ll gladly tolerate the slight noise from the Nepton’s pump, since it’s the only audible sound from this cooler (at least when the CPU underneath is at stock clock speeds). If everything in my PC was this quiet, I’d be pinching myself.

Conclusions

The liquid-cooling mad scientists to whom I paid homage at the beginning of my review might disavow the Nepton 240M, but they might also admit a grudging respect for a product that makes harnessing the power of liquid cooling so easy—and performs so well.

The Nepton 240M’s Silencio 120 fans are a noticeable step up from the basic spinner of the Seidon 120V, and the ritzier pump technology in the Nepton makes for a smoother-sounding, quieter experience, as well. The 240M’s mounting system is logical and a snap to install. When compared to the Seidon 120V, the Nepton’s extra radiator area allowed it to keep the AMD A10-7850K cooler under load without moving its fans off idle. Astounding.

Cooler Master Nepton 240M October 2014

My only problem—and I’m really stretching here—was with the Nepton 240M’s rubber fan gasket. Working with that gasket was annoying enough that I eventually set it aside. While my tests didn’t cause the fans to spin up at all, demanding overclocks might be a different story, and I’ll be curious to see whether the gasket signficantly affects the 240M’s noise character in those situations. If it does, Cooler Master might want to make this gasket easier to install in situations where the fans can’t be secured to the radiator first.

All told, though, I’d put a Nepton 240M in my own PC without hesitation. Well, maybe a little hesitation. $130 is a lot to ask for a CPU cooler, but the Nepton delivers performance equal to its lofty price. The only open question I have is how well the Nepton stands up to an overclocked CPU. In the unlikely event that the 240M stumbles with a hot-clocked processor underneath, I reserve the right to change my mind. But for now, the Nepton 240M is TR Recommended.