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3-Way Low Profile CPU Cooling Shoot-Out: Reeven, Phanteks, Noctua

A good CPU cooler can usually be found at the top spots of an enthusiast’s shopping list, as stock coolers rarely are sufficient for the wants and needs of advanced users, especially when overclocking is involved. Choosing the right aftermarket product can be a little complicated, mostly depending on what the product’s focus is and the available budget. For example, some products have been designed to be as quiet as possible while others strictly aim for maximum thermal performance and neglect acoustic comfort completely. Even if two coolers cost about the same, their behavior can be radically different, and it falls to the user to make a judicious choice according to his/her needs.

Whether the focus of the user is quieter operation or higher thermal performance, there is another factor that can make the purchase of a good cooler complicated: size. Sometimes you cannot just buy the best cooler for the job for the simple reason that it will not fit into the system. This is particularly true for compact and/or narrow cases, especially those meant for ITX systems and horizontal placement. With the majority of typical CPU coolers being tower-type constructs, it is difficult to find one that fits inside compact case designs.

To combat this, many manufacturers designed and produced horizontal coolers, i.e. coolers with the fin array placed horizontally instead of vertically. Horizontal coolers are much shorter than typical tower coolers and tend to cool the motherboard’s parts better as well, yet rumor has it that they do not perform as well as tower coolers. The truth is that size/mass is a major factor here as well, meaning that the horizontal designs are meant to be compact and usually just lack the mass of comparable tower cooler designs.

In today's review we will explore three such lower-profile coolers; the Reeven Steropes RC-1206b, the Phanteks PH-TC12LS and the Noctua NH-C14S. These horizontal coolers are all meant for desktop/HTPC designs but they also are significantly different in terms of size, with the Steropes starting at 60 mm tall, moving up to 74 mm with the PH-TC12LS and jumping up to 115/142 mm with the NH-C14S. In the following pages we will explore their design, quality and performance.

Horizontal GPU Cooler Roundup
  Reeven Steropes RC-1206b Phanteks PH-TC12LS Noctua NH-C14S
Fan(s) (mm) 120 (low profile) 120 140
Fan Speed (RPM) 2000 1800 1500
Height (mm/in) 60/2.4 74/2.9 115/4.53
Current Retail Price $40 $40 $75

The Reeven Steropes RC-1206b

Reeven supplies the Steropes inside a dark cardboard box, with the aesthetic design following the black/gold theme of the brand. The box is small, but it is a lightweight cooler that is very well packed inside the box, so shipping protection is more than sufficient. The bundle accompanying the Steropes is Spartan, comprised only by a black and white leaflet with installation instructions, the necessary mounting hardware and a single dose of thermal compound.


The Steropes is a horizontal cooler that has been designed to offer the best possible performance within a height of only 60 mm, offering maximum compatibility where size is a major consideration. With Reeven strongly advertising its socket AM1 compatibility, the Steropes appears to have been designed so that it could be a performance choice for very compact ITX/mATX systems, not to compete with its more sizable counterparts. Due to its shape and design, the Steropes is wider than the CPU socket area of small motherboards, but the fins are (just barely) high enough to allow for the installation of standard height RAM modules beneath it.

The fin array is relatively dense but the fins are narrow, a fitting choice since the goal of a heatsink is to maximize the surface area for heat dissipation. The fins are thin and flimsy but, for aesthetic purposes more than mechanical cohesion, the designer added a much thicker fin at the beginning of the array with the company logo punched on it. In order to further reduce the size of the cooler, Reeven is using a low profile 120 mm fan as well.

For a little extra performance, the base of the heatsink resembles a small heatsink all by itself. Considering how narrow the cooler is, airflow from the fan will certainly find its way down to the heatsink on the base of the cooler and should assist with thermal dissipation, even if only barely. Five heatpipes exit the small base of the cooler, with the three of them expanding towards both sides of the base, concurrently reaching into the fin array from the side and from the bottom.

A close inspection of the base reveals that only the heatpipes and the plate that makes contact with the processor are made out of nickel-plated copper. The rest of the Steropes, including the small heatsink on its base, is aluminum. The base of the cooler is very well made, finished down to a well-polished surface. 

The Phanteks PH-TC12LS

We received the Phanteks TC12LS inside a dark cardboard box with an abstract aesthetic theme, mostly based on schematic drawings of the cooler itself. Considering the size of the cooler, the box is large, with excessive layers of polystyrene foam for protection found on the inside. Inside the box we found four manuals, one for each of the most popular languages in the regions that the cooler is being marketed into, the necessary mounting hardware, and a syringe with Phanteks PH-NDC thermal compound that should last for at least three or four applications.


The Phanteks TC12LS features a narrow, dense array of black aluminum fins, much like the one we saw on Steropes, yet is even smaller. The fins are relatively thin but strong, with their sides rolled so that they support each other, virtually amassing together into a single strong construct. There are small gaps towards the center of the array to allow for a screwdriver to go through for the installation of the cooler, further reducing the surface of the array. Again, the TC12LS is wider than the CPU socket area of small motherboards, but the fin array is high enough to allow for the installation of standard height RAM modules beneath it.

A major marketing point of the TC12LS is its fan. Phanteks is using a full size 120 mm fan, and not just any 120 mm fan, but the PH-F120MP, one of their more advanced high performance designs. The PH-F120MP is a high static pressure design that may be quite a bit of an overkill for the narrow heatsink of the TC12LS, but should maintain good performance at lower RPMs.

Six 6 mm thick nickel-plated copper heatpipes exit the small base of the TC12LS, entering the fin array from one side. Rounded metallic caps cover their endings, mostly for aesthetic purposes.

The base of the TC12LS is not solid. A close inspection reveals that it comprises of two parts, the copper base and an aluminum top, with the heatpipes sandwiched between them. The aluminum top is flat and only meant to offer mechanical cohesion and mounting functionality, not to directly aid the thermal performance of the cooler in the slightest. The contact surface is machined well, down to a very smooth, flawless surface.

The Noctua NH-C14S

The sheer size of the box hints that the Noctua NH-C14S is not a very compact construct. Much like nearly all of Noctua’s products, the artwork on the box is austere, limited to providing useful information about the cooler itself. Inside the box everything is individually packed into separate cardboard boxes. Alongside with the mounting hardware, Noctua is also offering a basic screwdriver for the installation of the cooler, a fan speed reducer, a metallic case badge and a syringe with NT-H1 thermal compound.


Unlike the other two coolers in this review, the Noctua NH-C14S has not been designed to be very compact, but to fill the gap between low-profile coolers and standard tower coolers for users that purchased relatively tall/wide HTPC cases. Although its core design is similar to that of other horizontal coolers, the fin array is wider and much thicker, offering more than three times as much surface area as very low profile coolers. Two small holes can be seen halfway through the array, meant for the provided screwdriver to go through from and reach the screws at the base of the cooler. The first fin of the array is not physically different than the rest, but it does have the company logo punched onto it.

The NH-C14S has a single 140 mm NF-A14 PWM fan installed. The major twist with the design of the NH-C14S is the position of the fan, which is underneath the fin array and is pushing the air upwards through it. Still, standard RAM modules will fit underneath the NH-C14S. The user has the option to place the fan (or another fan) at the top of the fin array, increasing the clearance of the RAM modules by 25 mm but adding the same height to the overall height of the cooler. With the fan at the top of the array, RAM modules up to 70 mm tall can fit, allowing greater hardware compatibility if the case can support a cooler that is 142 mm tall.

Noctua’s Secufirm2 mounting system design has the cooler ready for installation, with the mounting braces and screws already waiting on the base of the cooler. Six nickel plated heatpipes are sandwiched between the copper base of the cooler and its bulky aluminum top. The machining of the base is flawless, without even the slightest imperfection to be found upon close inspection. It seems that the contact surface has been worked from the center out. Although it has not a mirror finish, it is extremely smooth and difficult to soil.

Testing Methodology

Although the testing of a cooler appears to be a simple task, that could not be much further from the truth. Proper thermal testing cannot be performed with a cooler mounted on a single chip, for multiple reasons. Some of these reasons include the instability of the thermal load and the inability to fully control and or monitor it, as well as the inaccuracy of the chip-integrated sensors. It is also impossible to compare results taken on different chips, let alone entirely different systems, which is a great problem when testing computer coolers, as the hardware changes every several months. Finally, testing a cooler on a typical system prevents the tester from assessing the most vital characteristic of a cooler, its absolute thermal resistance.

The absolute thermal resistance defines the absolute performance of a heatsink by indicating the temperature rise per unit of power, in our case in degrees Celsius per Watt (°C/W). In layman's terms, if the thermal resistance of a heatsink is known, the user can assess the highest possible temperature rise of a chip over ambient by simply multiplying the maximum thermal design power (TDP) rating of the chip with it. Extracting the absolute thermal resistance of a cooler however is no simple task, as the load has to be perfectly even, steady and variable, as the thermal resistance also varies depending on the magnitude of the thermal load. Therefore, even if it would be possible to assess the thermal resistance of a cooler while it is mounted on a working chip, it would not suffice, as a large change of the thermal load can yield much different results.

Appropriate thermal testing requires the creation of a proper testing station and the use of laboratory-grade equipment. Therefore, we created a thermal testing platform with a fully controllable thermal energy source that may be used to test any kind of cooler, regardless of its design and or compatibility. The thermal cartridge inside the core of our testing station can have its power adjusted between 60 W and 340 W, in 2 W increments (and it never throttles). Furthermore, monitoring and logging of the testing process via software minimizes the possibility of human errors during testing. A multifunction data acquisition module (DAQ) is responsible for the automatic or the manual control of the testing equipment, the acquisition of the ambient and the in-core temperatures via PT100 sensors, the logging of the test results and the mathematical extraction of performance figures.

Finally, as noise measurements are a bit tricky, their measurement is being performed only manually. Fans can have significant variations in speed from their rated values, thus their actual speed during the thermal testing is being acquired via a laser tachometer. The fans (and pumps, when applicable) are being powered via an adjustable, fanless desktop DC power supply and noise measurements are being taken 1 meter away from the cooler, in a straight line ahead from its fan engine. At this point we should also note that the Decibel scale is logarithmic, which means that roughly every 3 dB(A) the sound pressure doubles. Therefore, the difference of sound pressure between 30 dB(A) and 60 dB(A) is not "twice as much" but nearly a thousand times greater. The table below should help you cross-reference our test results with real-life situations.

The noise floor of our recording equipment is 30.2-30.4 dB(A), which represents a medium-sized room without any active noise sources. All of our acoustic testing takes place during night hours, minimizing the possibility of external disruptions.

<35dB(A) Virtually inaudible
35-38dB(A) Very quiet (whisper-slight humming)
38-40dB(A) Quiet (relatively comfortable – humming)
40-44dB(A) Normal (humming noise, above comfortable for a large % of users)
44-47dB(A)* Loud* (strong aerodynamic noise)
47-50dB(A) Very loud (strong whining noise)
50-54dB(A) Extremely loud (painfully distracting for the vast majority of users)
>54dB(A) Intolerable for home/office use, special applications only.

*noise levels above this are not suggested for daily use

Testing Results, Maximum Fan Speed (12 Volts)

We'll start things off with a look at cooling performance with each cooler's fan running at their maxiumum 12V fan speed.

Average Thermal Resistance

Right off the bat, when it comes to thermal resistance we can see that Noctua's NH-C14S cooler is well ahead of the rest of the pack. Which isn't too surprising given just how much larger it is than the other coolers we're looking at today.

Core Temperature, Constant Thermal Load (Max Fan Speed)
60 W Load100 W Load150 W Load200 W Load250 W Load340 W Load

At a 60 watt load – roughly the TDP of most desktop CPUs these days – the results roughly mirror thermal resistance. That said, even the weakest cooler is only 13C over ambient, which is a good result here.

Fan Speed (12 Volts)

Noise level

Ultimately with every cooler’s fan running at its maximum speed, the Reeven Steropes and the Phanteks TC12LS perform similarly, with the former showing a little better thermal performance despite its low profile 120 mm fan. This small advantage of the Reeven Steropes is being achieved via brute force, as its low profile fan is faster and disproportionally louder than Phanteks’ PH-F120MP. Comparatively, when compared to other advanced coolers that we have reviewed to this date, both the Reeven Steropes and the Phanteks PH-TC12LS can only be compared to the stock AMD Wraith cooler, and even then the Wraith outperforms them both. However, they do significantly outperform standard stock coolers.

Noctua’s NH-C14S is in an entirely different league. The comparatively huge mass of the cooler and the excellent NF-A14 fan offer the NH-C14S a tremendous performance advantage. As a matter of fact, the NH-C14S is a threat to many large tower coolers, outperforming the Cooler Master EVO 212 by a significant margin and touching the performance of the Grandis and the Dark Rock Pro 3, all while maintaining reasonably low noise levels.

Testing Results, Low Fan Speed (7 Volts)

Switching things up, let's take a look at cooling performance with the fans brought down to 7 Volts, for a look at performance with quieter operation.

Average Thermal Resistance

As you'd expect, the average thermal resistance rises with the reduced airflow. The Noctua is still in a league of its own here due to its size. Meanwhile the Phanteks struggles some, as it comes in at the bottom of this chart.

Core Temperature, Constant Thermal Load (Low Fan Speed)
60 W Load100 W Load150 W Load200 W Load250 W Load340 W Load

Core temperatures still look good, though. With the Noctua well in the lead, the other two coolers are only about 19C over ambient at 60W, which bodes particularly well for quiet computing at stock clocks.

Fan Speed (7 Volts)

Noise level

While we had to skip two of our highest wattage tests here – these low profile coolers simply aren't meant for highly overclocked & overvolted processors – ultimately the results from our tests show that all of the coolers are sufficient for their jobs. Though smaller, neither the Phanteks or Reeven coolers would have any issue cooling a modern processor running at stock speed, even in low airflow environments. Again, the Reeven Steropes has the advantage over the Phanteks TC12LS in terms of raw thermal performance, but the latter is significantly quieter, reaching virtually inaudible noise levels.

As for the Noctua NH-C14S, with its fans running at low speed, the performance gap between the NH-C14S and the other horizontal coolers widened greatly, to the point that it would be unfair to make any comparisons at all. The NH-C14S is only comparable to large tower coolers, thermally outperforming even very large coolers with much greater mass. The noise output of the NF-A14 fan under these conditions is very low and should be barely noticeable in a very quiet room.


Although horizontal CPU coolers are likely to always remain a niche market, the continued growth in and shift to smaller form factor PCs has given them a higher profile among system builders as of late. These lower-profile coolers give users additional options for builds that are facing height constrains while the builder wants or needs better than stock cooling. Each of the three coolers in this review requires a different amount of vertical clearance, starting from just 60 mm and reaching up to 115 mm, thus each of them is practically meant for a specific case design.

The Reeven Steropes is the shortest cooler of this review, requiring just 60 mm of clearance. Reeven achieved this by installing a low profile cooler on the narrow fin array, reducing the overall height of the cooler down to the absolute minimum, allowing compatibility with even the narrowest of HTPC cases. The fin array is barely high enough to allow for normal height RAM modules to be installed beneath it and barely wide enough to enclose the heatpipes. Still, despite the low static pressure of the low profile fan, Reeven’s engineers cleverly stole a little bit of performance by expanding three of the heatpipes to carry some of the thermal energy to the center of the fin array and by turning the base of the Steropes into a small heatsink. The result is a very low profile cooler that offers remarkably good thermal performance for the size. Its compatibility with the AM1 socket suggests that the Steropes is one of the best aftermarket options for these systems, with thermal performance that would be a complete overkill on these low power CPUs.

Phanteks’ PH-TC12LS is of similar size and shape to the Steropes, but designed with a full size 120 mm fan instead. This raises the required clearance to 74 mm, making the PH-TC12LS incompatible with very narrow HTPC cases, but it should fit in most ITX/HTPC cases that are meant for performance PCs. The PH-F120MP high static pressure fan allows the PH-TC12LS to achieve good performance figures while maintaining reasonable noise levels. The design is being let down by its simple, small fin array that does not offer enough surface area for heat dissipation, reducing the effectiveness of the high airflow produced by the fan. Overall, the thermal performance of the PH-TC12LS is good in relation to its size, but we feel that the design is unbalanced and that it could be fine-tuned to perform even better.

The third cooler of our review, the Noctua NH-C14S, is virtually incomparable with the previous two coolers. It has over twice the mass of the other coolers and requires a much greater vertical clearance – at least 115 mm depending on configuration – instantly ruling it out as an option for the vast majority of HTPC cases and other narrow designs. If the fan were to be placed at the top of the cooler in order to increase the clearance of the RAM modules, it is unlikely that the NH-C14S will be compatible with any desktop or HTPC case, as it would not even fit inside designs that are meant for top-tier HTPCs. It is apparent that Noctua has designed the NH-C14S solely for users that are planning to build very high performance HTPC system with sizable cases and want a product that can compare to high performance tower coolers. Naturally, it cannot reach the performance of coolers such as the NH-D15 or the Cryorig R1 Ultimate, but it does get close enough to warrant excellent performance on any CPU currently available, overclocked or not. It is an expensive cooler but the quality and performance are well worth the money. The true enemy of the NH-C14S is its size, which makes it incompatible with most of the cases that have been designed for compact or HTPC systems, reducing its potential market down to the few users that own spacious HTPC cases. 


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