DeepCool Assassin IV – The almost perfect CPU cooler

Pavel Sekerka

10 months ago

Key Features

The long awaited DeepCool Assassin IV cooler is finally here. According to the manufacturer it should offer very quiet operation with high cooling effectiveness and it is also an interesting piece visually. In today’s review I’m going to subject it to a thorough analysis and examine the manufacturer’s bet on an unconventional cooler design. I’m also expanding the stress tests to include a wider range of noise levels and a spectral analysis of the cooler.

Key features of the cooler

The Assassin IV is the new flagship and nicely rounds out the top of DeepCool’s updated cooler lineup. It is a direct successor to the Assassin III cooler I also tested here, but the two coolers couldn’t be less similar. While the Assassin III is a typical dual-tower cooler in a conventional push/push configuration (both fans push air through one of the heatsink towers) with a symmetrical fan setup, the Assassin IV relies on a completely atypical design. Also, while it is a dual-tower cooler, each heatsink tower is differently thick. Both fans are now mounted in a pull/pull configuration (i.e. both fans draw air through the heatsink towers) and it is an asymmetrical setup of a 140mm and a 120mm fan.

The entire cooler is matte black except for the nickel-plated copper base with a large heat exchange surface that is intersected by a total of seven 6mm heatpipes. Visually, this cooler fits in with the minimalist futuristic design of current DeepCool coolers. Simply put, it looks like a large black cube with perforations in the middle section. With no standard fan mounted on the front tower, you can enjoy the sight of the matrix pattern of the heatsink fins.

A rear view of the cooler reveals a 120mm fan with reversed rotor blade orientation. The fan is housed in a plastic frame that also serves as a clamping mechanism to the cooler shroud. Additionally, it can be moved to a higher position should there be a physical incompatibility between the cooler and a too-high VRM heatsink. If you would like to replace the rear fan with another fan, that is possible, but you need to be mindful of the fan orientation to ensure proper airflow away from the rear cooler tower.

The view from above reveals several interesting features. One of them is the magnetically attached perforated shroud for access to the center 140mm fan. Thanks to the absence of any clamping mechanism, there is no disturbance to the appearance of the cooler. On the top surface of the shroud near the front tower you can notice a small sliding dial. This is an integrated fan speed limiter that also serves as a splitter for both fans, so you only need a single PWM header on the motherboard. The last interesting feature on the top surface of the cooler is the unobtrusive manufacturer’s logo. Its backlight intensity depends on the speed range you set on the limiter and it’s just a shame that it’s not an RGB LED, but only glows in a shade of green like the DeepCool logo.

The middle 140mm fan is attached to the cooler by flexible tabs and rubber corners to prevent vibration transfer to the heatsink. So you don’t need any tools to remove it, and removing it also gives you easy access to the cooler mounting system with screws that are integrated into the base of the cooler and equipped with springs for optimal pressure.

The package contents of the DeepCool Assassin IV is a perfect example of what it should look like for all high-end coolers without exception. The supplied accessories are plentiful and there is nothing missing. The mounting system for installing the cooler is sturdy and completely made of metal with the exception of the plastic end caps on the backplate for Intel sockets. However, these end caps do not carry any weight of the cooler and only serve as a positioning element for the screws according to the spacing of the CPU socket mounting holes.

A nice bonus is the handy combination screwdriver for easy mounting, and you will also find a tube of DeepCool DM9 thermal paste, including an applicator and cleaning cloth for optimal preparation of the CPU heat spreader area. A pleasant surprise was the presence of a plastic frame for an additional 120mm fan on the front tower of the cooler, including a set of self-tapping screws for its mounting. This frame can be installed at any height on the front tower as needed to avoid conflict with RAM modules, just keep in mind that this will logically increase the overall height of the cooler. The accessories are rounded off by a detailed and clear manual.

Mounting the cooler is simple and should be no problem for you. Just select the appropriate kit according to the processor socket and for Intel processors use the supplied backplate. As already hinted in the previous text, you have to remove the middle 140mm fan from the cooler for installation. For this part, it is advisable to use the supplied screwdriver or another sufficiently long tool with a PH2 tip.

Cooler and fan parameters

DeepCool Assassin IV is a surprisingly dense cooler. Although it is smaller in all dimensions than, for example, Cooler Master’s MasterAir MA824 Stealth or Noctua’s NH-D15 chromax.black, it doesn’t lag behind in weight, quite the opposite. That’s also why I’m glad that it comes with a really robust mounting system. The big advantage is also 100% compatibility with RAM modules on common Intel and AMD sockets. You only have to be careful with the (now practically obsolete) Intel LGA 20xx socket, where you are limited by the position of the rear fan. It can be moved to a higher position if necessary, if you have enough space in the case.


Cooler	DeepCool Assassin IV	Noctua NH-D15 chromax.black	Cooler Master MA824 Stealth
Supported sockets	Intel LGA 115x, 1200, 1700, 20xx; AMD AM4/AM5
Height	164 mm	165 mm	166 mm
Width	144 mm	150 mm	151 mm
Depth with fan	147 mm	161 mm	162 mm
Weight	1575 g	1320 g	1630 g
Maximum RAM height	no limit (except Intel LGA 20xx socket)	acc. to front fan position (keep in mind the cooler's total height)
MSRP	109 EUR	119 EUR	109 EUR

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Unlike its predecessor (Assassin III), the DeepCool Assassin IV now uses a combination of two different fans. In the middle of the cooler between the heatsink towers is a 140mm fan with a circular frame, and behind the rear tower is a smaller 120mm fan of conventional design. Both are plugged into an integrated splitter in the cooler, so you only need a single PWM header on the motherboard. This splitter also serves as a maximum speed limiter to about 1350 RPM.


Fan	DFr140/DF120	Noctua NF-A15-HS	Mobius 135/120
Bearing	fluid	SSO2	LDB
Speed range	500–1700 rpm	300–1500 rpm	0–1550/1950 rpm
Max. airflow	134.4/98.6 m³/h	140.2 m³/h	108.0/107.2 m³/h
Max. static pressure	2.44/2.10 mm H₂O	2.08 mm H₂O	1.92/2.69 mm H₂O

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Testing methodology

As a test processor and heat generator I use the Intel Core i7-11700K in the Asus TUF Gaming Z590-Plus WIFI motherboard. The entire build is mounted on a Streacom BC1 frame with no fans to provide airflow. Acoustic shielding (acoustic foam on OSB boards) is installed around the test build to eliminate ambient noise. A calibrated Voltcraft SL-100 noise meter is placed perpendicular to the cooler in a fixed position relative to the motherboard at a distance of approximately 35 cm from the processor socket.

Stress tests are performed using the Prime95 application with a duration of 30–35 minutes. Coolers are tested at three standardized noise levels (36, 39 and 42 dBA) and finally at maximum speed. In addition, I am gradually adding tests at 45 and 48 dBA levels and you will also find this data in the results over time. The tests are run in two sets based on the thermal output of the processor.

The first set of tests is at 125 W, the forced PL1 limit. The second set of tests is then at about 210 W (4500 MHz at 1.285 V). However, this second level represents a very high concentration of heat per mm2 due to the small size of the chip itself. Thus, not all coolers can be expected to pass this set of tests at all noise levels. For example, no cooler reached the 36 dBA level at this load, and for that I eventually eliminated it from the tests after some consideration.

The highest temperature reached is always recorded at the end of the test. All data regarding temperatures and thermal output of the processor are obtained from the HWiNFO64 application. The measured values are then corrected against the room temperature as the resulting Delta T value. Any higher value means a risk of processor temperature above 95–100 °C and a risk of thermal throttling. Therefore, if the cooler does not pass the load with a Delta T value below 75 °C, such a test is marked as a failure.

Results – 36 dBA

In this category you will no longer find results of stress tests at 210 W. The reason for this is the impossibility to achieve such low noise at very high load with any cooler I had the opportunity to test, even with the best 360mm AIOs. However, the results at 125W load understandably remain, and if no value is listed for the cooler, it means that it could not be tuned to such a low noise level.

Why is there a missing value for a cooler in the chart? Because the cooler could no longer handle the load in the specified mode, or because the fan could not be slowed down to the required level, this is typically the mode with the lowest noise level.

Results – 39 dBA

Results – 42 dBA

Results – 45, 48 and 51 dBA

I’ve also conceived today’s review as a battle of titans. In the chart below you’ll find the results of the three top air coolers I tested, and I’d like to expand this dataset in the near future with the results of the BeQuiet! Dark Rock 4 Pro. With the Noctua NH-D15, the age of the design and the fans used are starting to show, after all next year this cooler will celebrate ten years since its introduction. However, it still holds its own with coolers with more modern designs and puts up a very close fight with them. Don’t be fooled by the scale of the chart, which I have deliberately chosen to make the small differences stand out, all three coolers give top-notch results.

Results – maximum speed

Spectral analysis of noise

Also new today is a spectral analysis of the noise of the cooler, and you will find this analysis in every review from now on. This is a simple analysis at noise levels of 39 dBA, 45 dBA and at maximum speed of the cooler. For the analysis I use the UMIK-1 microphone from miniDPS in conjunction with True Audio’s TrueRTA application. The resolution of the analysis is 1/24 of an octave and the shape of the spectrogram is an average of 100 samples acquired over 20–30 seconds.

So first, let’s take a look at the DeepCool Assassin IV. The acoustics of the cooler come with more pronounced peaks in the lower frequency range around 175–250 Hz, resulting in the cooler exhibiting a subjective rumbly character. This is true even at the low noise level at 39 dBA. With higher fan speeds, the tonal peaks shift to higher frequencies around 2.5–6 kHz, which is likely due to the resonance of the airflow through the heatsink. And the smaller tonal peaks in the higher frequencies are probably due to the design of the heatsink, where the airflow exiting it is being sliced by the rear fan blades. Unfortunately, the cooler is subjectively noisier than the acoustic measurement shows.

The Cooler Master MasterAir MA824 Stealth is a bit better acoustically, but also subjectively a bit rumbly. Fortunately, it doesn’t have such high peaks in the band from 1 kHz to 5 kHz, which the human ear perceives most sensitively. At lower speeds, its acoustically expression is generally a bit more pleasant.

And finally, we have a classic in the form of the Noctua NH-D15 cooler. The acoustic performance of this cooler is very similar to the MA824, but with a slightly smoother characteristic at higher speeds. Overall, it comes out the best out of this trio, especially in terms of subjective noise perception.

Conclusion and evaluation

DeepCool Assassin IV certainly lived up to the high expectations, meaning great results in stress tests, high build quality, a robust mounting system and a wealth of accessories. While this cooler didn’t beat Cooler Master’s MasterAir MA824 Stealth in absolute numbers, it remains a very close second.

If we add a nearly decade old classic in the form of the Noctua NH-D15 cooler to the comparison, we see a clear shift in the development of modern coolers and overall it is a pretty evenly matched battle of three titans. Want maximum cooling no matter what? Take the MA824. Do you want the best acoustics and don’t mind slightly higher temperatures? Reach for the NH-D15. Want a high-performance cooler that also looks great and offers interesting details? Go for the Assassin IV.

DeepCool Assassin IV is simply one of the best coolers on the market. Its only flaw is the suboptimal acoustic expression of the fans at higher speeds. However, this is a near perfect cooler that, if we cut it some slack, deserves our highest praise.

English translation and edit by Jozef Dudáš


DeepCool Assassin IV
+ Great cooling performance
+ Creative structure details
+ Plentiful accessories
+ Attractive design
+ Integrated splitter/speed limiter
- Worse acoustic profile of the fans

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