NZXT’s Kraken X72 closed-loop liquid cooler is another in the XX2 series, following the 280mm X62 that we previously reviewed. The X72 is a 360mm cooler, putting it in more direct competition with the Corsair H150i Pro (the first to feature a 6th-gen pump) and Fractal S36, and indirect competition – in performance only – with the EVGA CLC 280.
NZXT’s X72 costs $200, making it one of the most expensive CLCs on the market. The Floe 360 lands at around $184, the EK Phoenix 360 – a semi-open solution – is the only one that lands significantly higher. The X72 still uses the same pump design as when we tore-down the X42, running Asetek’s 5th Gen pump and a custom, NZXT-designed PCB for RGB lighting effects. Functionally, 5th Gen has proven to be marginally superior – technically – to its 6th Gen for outright cooling performance. We’re talking nearly margins of error. The newest generation is presently only used on Corsair’s H150i and H115i Pro products, as Corsair largely dictated what went into the 6th generation. Major differences are made-up by the metal impeller, similar to the one used by Dynatron in old Antec Kuhler products, rather than a 3-prong plastic impeller. These don’t perform differently in terms of thermals, but there should be reduced susceptibility to heated liquid, and theoretically reduced hotspots as a result of the new 6th Generation design. That doesn’t manifest in outright performance, but might manifest in endurance. We won’t know for a few years, realistically.
Our primary tests for the NZXT Kraken X72 review and benchmark include the following:
- 100% fan / 100% pump
- 100% fan / silent pump
- 63% fan (40dBA)
Corsair’s H115i Pro launched alongside the H150i Pro, the first two closed-loop liquid coolers to use the Asetek 6th-Gen pump. As we said in the H150i Pro review, Asetek didn’t do Corsair any favors, here – the new pump isn’t much different from the old one, and primarily focuses on RGB implementations akin to NZXT’s custom work on the XX2 series. Regardless, Corsair has taken this and used it as an opportunity to bundle their new CLCs with silence-focused fans, the ML120 Pro fans.
As shown in our tear-down of the 6th Gen Asetek pump, where we took apart the H150i Pro, the primary changes of the pump are endurance-focused, not performance-focused. Asetek is ultimately the supplier, here, and that means Corsair’s main contributions are restricted to fan choice; that said, Corsair did dictate large parts of the 6th Generation design. Asetek now includes an RGB LED kit for manufacturers, and also includes the PCB for programmable LEDs (something that NZXT previously went through great effort to customize on the 5th generation). The 6th Gen Corsair coldplate is also marginally smaller than the fifth generation, but other than that, it’s all endurance-driven. Asetek has changed its impeller to a metal option, similar to the old Dynatron impellers in the Antec 1250 Kuhler series. Asetek has also reportedly “optimized” their liquid paths to reduce hotspots that caused higher permeation than desired in older generations.
In terms of performance, though, our extensive testing results (and our contacts) all indicate that the 6th Generation is not an improvement in cooling. At best, they’re the same. And that’s at best.
Under guidelines by AMD that we could show Threadripper CPU installation and cooler installation, we figured it’d also be pertinent to show cooler coverage on TR and RAM clearance. These all fall under the “installation” bucket and normally wouldn’t get attention from us, but Threadripper’s uniquely sized socket with uniquely positioned dies demands more instruction.
Threadripper thermal compound & coldplate coverage has been a primary topic of discussion since we first showed motherboards at Computex. We’ve generally offered that, theoretically, coldplate coverage should be “fine” as long as the two Threadripper CPU dies are adequately covered by the coldplate. In order to determine once and for all whether Asetek coolers will cover the IHS appropriately, seeing as that’s what TR ships with, we mapped out the dies on one of our samples, then compared that to CLC thermal paste silk screens, coldplates, and applied thermal compound.
GamersNexus today received word from a manufacturer (that asked to remain unnamed) that AMD’s Threadripper CPUs will include Asetek retention kits in the retail packaging for the product, though a cooler itself will not be included; at least, not in the initial launch of Threadripper products. From what we’ve seen of AMD’s unveiled box, it’s clear that no cooler is included, but the Asetek retention kit will permit all Asetek-made CLCs to mount Threadripper at launch. This would include popular products like the NZXT Kraken series, EVGA CLC series, and about half of Corsair’s coolers (the other half being CoolIT-made). The H100iV2 and H115i are included in the list of Asetek-made Corsair coolers, for clarity.
When we made our “how air coolers work” video, a lot of viewers were interested in the inner workings of copper heatpipes and their various means of facilitating capillary action. Today, we’re revisiting our TLDR series with a video on how closed-loop liquid coolers work. We’ll be talking about permeation, air pockets, stators, impellers, coldplates, and chemical composition of the coolant.
This content has custom-made animations that we rendered specifically for explanation of how CLCs work. GN’s Andrew Coleman modeled and animated a closed-loop cooler for the piece, referencing NZXT’s Kraken X52. Because of the level of detail and custom animations of this content, NZXT sponsored GN to put this piece together. The content applies to all liquid coolers, but particularly focuses on closed-loop products; all concepts herein can be applied to CLCs across the industry from various suppliers and manufacturers. Our technical deep-dive for today serves as a means to fully detail liquid cooling and how it works, drilling down to piano-wire granularity (literally).
Fractal’s Celsius S36 debuts alongside the company’s S24, coolers sized at 360mm and 240mm, respectively. The Celsius series uses an Asetek Gen5 pump, identical to the pump found on the EVGA CLC, NZXT X42/52/62, and Corsair H115i/H100iV2 coolers. This is a semi-custom Asetek solution that’s been loosely customized by Fractal Design, primarily focusing on the addition of G1/4” fittings (rad-side only), on-pump speed tuning, and an on-rad fan hub. It’s not as customized as, say, the NZXT Kraken series, but NZXT’s products also run more expensive. Fractal is looking at a launch price of $120 for the S36 that we’re reviewing today, and $110 for the S24.
Our focuses are on thermals and noise – not that you can focus on much else when talking coolers – with some new testing that looks at normalized noise output. We debuted this testing in our ASUS ROG Strix review and have carried it over to coolers.
Fractal’s coolers use 120mm fans that run a maximum RPM nearing 2000, with variable pump RPM from ~2000~3000. In our testing, though, it seemed a little simpler than that – pump RPM is based on liquid temp, and as we found in our 7700K review (the hottest CPU we've tested), liquid temp never really exceeds 30C. Given Fractal's curve, that means the pump stays at 2000RPM almost all the time. Rather than use software or suggest straight BIOS control – which we prefer – Fractal’s gone with a toggleable pump plate that switches into auto or PWM options. We’ve tested variable pump speeds in the past and haven’t found major differences in cooling efficacy, which is more heavily relegated to the fan spec and radiator size than anything else. This is more of a noise impact. We tested using the default, out-of-box “auto” setting, which kept our pump RPM fixed nearly perfectly at ~1960 throughout the tests (liquid temperature doesn't ramp up enough to push higher).
Fan speeds were manually controlled for the tests, though users could connect the fans to the on-rad hub. More on this in the conclusion.
Let’s get on with the testing, then run through the accessories and conclusion.
NZXT's new Kraken X42, X52, and X62 liquid coolers were announced today, all using the new Asetek Gen5 pump with substantial custom modifications. The most direct Gen5 competition would be from Corsair, makers of the H115i and H100iV2, each priced to compete with the Kraken X42 ($130) and X52. The Corsair units, however, are using an unmodified Asetek platform from top-to-bottom, aside from a couple of Corsair fans. NZXT's newest endeavor had its components dictated by NZXT, including a custom (and fairly complex) PCB for fan speed, pump speed, and RGB control, planted under a custom pump plate with infinity mirror finish. The unit has gone so far as to demand a double-elbow barb for pose-able tubes, rather than the out-the-top setup of the Asetek stock platform – that's some fastidious design.
As for how we know all of this, it's because we've already disassembled a unit. We decided to dismantle one of our test-complete models to learn about its internals, since we're still waiting for the X52 and X62 models to be review-ready. We've got a few more tests to run.
Before getting to the tear-down, let's run through the specs, price, and availability of NZXT's new Kraken X42, X52, and X62 closed-loop liquid coolers.
No reference card has impressed us this generation, insofar as usage by the enthusiast market. Primary complaints have consisted of thermal limitations or excessive heat generation, despite reasonable use cases with SIs and mITX form factor deployments. For our core audience, though, it's made more sense to recommend AIB partner models for superior cooling, pre-overclocks, and (normally) lower prices.
But that's not always the case – sometimes, as with today's review unit, the price climbs. This new child of Corsair and MSI carries on the Hydro GFX and Seahawk branding, respectively, and is posted at ~$750. The card is the construct of a partnership between the two companies, with MSI providing access to the GP104-400 chip and a reference board (FE PCB), and Corsair providing an H55 CLC and SP120L radiator fan. The companies sell their cards separately, but are selling the same product; MSI calls this the “Seahawk GTX 1080 ($750),” and Corsair sells only on its webstore as the “Hydro GFX GTX 1080.” The combination is one we first looked at with the Seahawk 980 Ti vs. the EVGA 980 Ti Hybrid, and we'll be making the EVGA FTW Hybrid vs. Hydro GFX 1080 comparison in the next few days.
For now, we're reviewing the Corsair Hydro GFX GTX 1080 liquid-cooled GPU for thermal performance, endurance throttles, noise, power, FPS, and overclocking potential. We will primarily refer to the card as the Hydro GFX, as Corsair is the company responsible for providing the loaner review sample. Know that it is the same as the Seahawk.
The EVGA Hybrid closed-loop liquid cooler has been the center of attention for a few of our DIY “Hybrid” mods, and for good reason: It was the best-performing CLC for GPUs that we tested last year, largely due to the protrusion in the coldplate and the dense microfins. The EVGA Hybrid cooler ($100) uses Asetek's supply, so we resurrected our old Corsair H100 (torn apart years ago) to compare a Generation 3 Asetek cooler to the new generation on EVGA's unit. You'll see that the setup is largely the same, though.
The EVGA Hybrid cooler we're tearing down today accompanies the GTX 980 Ti Hybrid, 970 Hybrid, and the forthcoming 1080 Hybrid. We managed to drop thermals of the GTX 1080 down to 18C (delta T over ambient) from ~57C by mounting an EVGA Hybrid cooler to the card, and even got an extra 100MHz out of our OC. Let's look at why that was the case.
We're building our own GTX 1080 Hybrid. We're impatient, and the potential for further improved clock-rate stability – not that the 1080 isn't already impressively stable – has drawn us toward a DIY solution. For this GTX 1080 liquid cooling mod, we're tearing apart $1300 worth of video cards: (1) the EVGA GTX 980 Ti Hybrid, which long held our Best of Bench award, is being sacrificed to the Pascal gods, and (2) the GTX 1080 Founders Edition shall be torn asunder, subjected to the whims of screwdrivers and liquid cooling.
Here's the deal: We ran a thermal throttle analysis in our 9000-word review of the GTX 1080 (read it!). We discovered that, like Maxwell before it, consumer Pascal seems to throttle its frequency as temperatures reach and exceed ~82C. Each hit at 82C triggered a frequency fluctuation of ~30~70MHz, enough to create a marginal hit to frametimes. This only happened a few times through our first endurance test, but we've conducted more – this time with overclocks applied – to see if there's ever a point at which the throttling goes from “welcomed safety check” to something less desirable.
Turns out, the thermal throttling impacts our overclocks, and it's limited the potential of a GPU that's otherwise a strong overclocker. And so begins Part 1 of our DIY GTX 1080 build log – disassembly; we're taking apart the GTX 1080, tearing it down to the bones for a closer look inside.
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