Fractal Design Define S Tower Case

Table of Contents

The latest edition of Fractal Design’s Define series takes the R5 and implements a more open airflow dynamic and improved watercooling compatibility.

May 18, 2015 by Lawrence Lee

Fractal Design Define S
ATX Tower Case
US$90 with window

When people ask SPCR to recommend an ATX tower, we think immediately of Fractal Design’s Define series. It hits all almost all the important case assets (for SPCR): no-nonsense aesthetics, modest size, reasonably good build quality, well-ventilated front panel, noise damping material, and built-in fan controller. The last two iterations, the Define R4 and R5, made 140 mm fan mounts standard on every side, and incorporated removable hard drive cages to improve graphics card compatibility. These two improvements increased its appeal to the lucrative gaming market but did so without tarnishing the underlying design.

The Define S.

The newest model, the Define S, hopes to gain traction with both budget users and watercooling enthusiasts. Physically, it looks just like the Define R5 with its recognizable ModuVent covers on the top of the case hiding each ceiling fan placement and numerous ventilation slits running down the sides of the front bezel. The physical dimensions are practically identical, as are the build materials. The Define S is a lower cost variant that lacks a fan controller and implements an interesting design twist. On the inside, all the drive cages and 5.25 inch bays have been taken out, so the front panel no longer functions as a door.

More importantly, this frees up the entire front portion of the case, allowing air to flow from up to three 140 mm fans, mostly unimpeded. 3.5 inch drives are mounted vertically on the right side of the case and there’s only space for three drives rather than eight on the R5. In the space vacated by the drive cages, Fractal has included mounting points so the area can repurposed for installing a pump and reservoir. At launch, they are only offering the Define S in black for a MSRP of US$80 for the standard model and US$90 for the windowed version, $30 cheaper than the R5.



Unfortunately I don’t have a picture of the retail box as it was too tightly hugged by the shipping box and extracting it wasn’t worth the effort. In any event, there’s nothing notable about the packaging. The side window is lined with a protective plastic covering on both sides, and it ships with a small accessory box and assembly guide. Fractal Design provides all the necessary and screws (save those for additional fans), a nut-driver for the brass standoffs, a handful of zip-ties, and reservoir mounting brackets.

Relevant Specifications: Fractal Design Define S
(from the
product web page
Motherboard Compatibility ATX, Micro ATX, Mini ITX
Expansion Slots 7
Drive Bays 3 x 2.5/3.5″ SSD/HDD
2 x 2.5″ SSD/HDD
Front Interface 2 USB 3.0
Audio in/out
Power button with LED (blue)
HDD activity LED (blue)
Reset button
Cooling Features 9 x fan positions (2 Fractal Design Dynamic GP14 140mm fans included); 8 fan positions on window model
Filtered fan slots in the front and bottom
Fan Positions Front: 3 x 120/140 mm fans (1 x 1000 RPM fan included)
Rear: 1 x 120/140 mm fan s (1 x 1000 RPM fan included)
Top: 3 x 120/140 mm fan (not included) or 1 – 180 mm fan with 165mm hole spacing (not included)
Bottom: 1 x120/140 mm fan (not included)
Side: 1 x120/140 mm fan (non-window version only, not included)
CPU Cooler Compatibility Up to 180 mm in height
PSU Compatibility ATX models up to 300 mm in length, 180/170 mm with a bottom 120/140mm fan installed
Graphics Card Compatibility Up to 450 mm in length, 425 mm with front fans installed directly in line with the GPU
With a front radiator, maximum graphics card length is reduced by the radiator thickness
Radiator Compatibility Front: 360, 280, 240, 140 and 120 mm, all thicknesses
Top: 420, 360, 280, 240, 140 and 120 mm (thickness limitation of 55 mm for both radiator + fan applies on 420, 280 and 140 mm models)
Bottom: 120 mm (use limits PSU length to 165 mm)
Rear: 120 or 140 mm
Pump Compatibility Pre-drilled holes on the bottom panel, supports many DDC and D5 variants
Reservoir Compatibility Adjustable mounting brackets allow for almost any rectangular mounting screw pattern
Maximum distance between the mounting bracket screw positions: 350mm height / 80mm width
Cable Management 20 – 40 mm of space for cable routing behind the motherboard plate
Velcro straps included for easy cable management
Colors Available Black
Package Contents Define S computer case
User manual
Accessory box
Case Dimensions
(W x H x D)
233 x 451 x 520 mm
233 x 465 x 533 mm with feet/screws/protrusions
Package Dimensions
(W x H x D)
322 x 615 x 535 mm
Net Weight 9.1 kg
Package Weight 10.8 kg


Like most towers, the Define S is a steel case with removable plastic panels at the front and top. Its dimensions are 46.5 x 23.3 x 53.3 cm or 18.3 x 9.2 x 21.0 inches (H x W x D), for a total volume of 57.7 Liters (the internal volume is a slightly smaller 54.6 Liters).

The plastic front bezel isn’t quite as thick as the R5’s door but it has the same faint vertical brush marks and ample ventilation along the sides.

The three fan placements at the top are covered by individual removable plastic panels.

The Define S has the same front interface except no USB 2.0 ports. Our sample also has some mysteriously faint curved lines along the top of the connectors/buttons that look almost like nail marks.

The Define S doesn’t have as much ventilation at the back and the rear fan position is fixed rather than adjustable. The side panels are held on with the same captive thumbscrews but the R5’s convenient locking mechanism is missing.

The R5 has a longer dust filter underneath to cover a second fan placement toward the front of the case, but the Define S uses that spot for a pump mount.

The side panels are 0.8~0.9 mm thick with a large window on one side and a 2 mm thick sheet of dense noise absorbent material on the other. The window is larger than on the R5, and could be more securely installed as it rattles a bit when you tap your fingers against the panel.


The internal construction of the Define S is reasonably solid and all the drive mounts, front/top panels, and filters fit snug. However, due to the way it’s designed, it’s not as structurally sound as the R5. Without any traditional drive bays to stiffen the frame, its hollowness makes it feel more flimsy, at least when it’s empty.

Beneath the front panel is a long dust filter with hinges on the right side and magnets on the left. There are three 120/140 mm fan mounts with rails rather than screw holes for minor positioning adjustments. [Editor’s Note: This may be the least restricted implementation of a major dust filter in any case we’ve seen in ages. The filter itself is the only thing standing between the fans and the vents slots around the front panel periphery. This is, in fact, an improvement in airflow potential over the R5.]

The ModuVents covers are lined with foam to keep noise out and help give the Define S a cleaner, more uniform look.

The interior looks pretty much as expected, just like the R5 but with all the drive bays pulled out. The motherboard tray now extends all the way to the front. There are some vertical slits cut out where the cages used to be, for added flexibility with regard to reservoir positioning.

At the back, the power supply exhaust port is fitted with an anti-vibration frame, and the expansion slot covers are ventilated and held on with individual thumbscrews.

Visible at the bottom of the case are rubber feet to elevate the power supply, while on the opposite side are mounting holes for both DDC and D5 pumps.

The area behind the motherboard tray is mostly the same except for an additional velcro strap at the bottom/rear, presumably for the 8-pin EPS12V cable. There are a pair of dedicated 2.5 inch drive mounts below the CPU cutout while three 2.5/3.5 inch drive brackets are located near the front.


The assembly process is fairly straightforward and easier than most cases due to the ample space. There are no drive cages and optical drive bays to get in the way and the area behind the motherboard tray fairly wide.

The 3.5 inch drives are mounted from underneath with screws and rubber grommets to limit vibration. Two metal tabs hook in at the bottom of each placement while a single thumbscrew at the top secures it in place.

This open airflow design is undoubtedly great for performance but without a custom watercooling loop, our finished system looks… unfinished. They probably could have included drive mounts on this side as well without interfering with airflow too much though the cabling would be more difficult to hide.

CPU heatsink clearance is an excessive 181 mm according to my measurements which not atypical for a tower with 140 mm fan compatibility at the back.

The provided velcro straps makes cable management an absolute pleasure compared to some cases.

After accounting for the foam on the right side panel, there’s a spacious 23 mm and 43 mm of clearance behind the motherboard tray and hard drive area, respectively.


System Configuration:

Test system device listing.

Measurement and Analysis Tools

  • Prime95
    processor stress software.
  • FurMark
    stability test to stress the integrated GPU.
  • Asus GPU Tweak to monitor GPU temperatures and adjust fan speeds.
  • SpeedFan
    to monitor system temperatures and adjust system fan speeds.
  • Extech 380803 AC power analyzer / data logger for measuring AC system
  • PC-based spectrum analyzer:
    SpectraPlus with ACO Pacific mic and M-Audio digitalaudio interfaces.
  • Anechoic chamber
    with ambient level of 11 dBA or lower

Testing Procedures

The system is placed in two states: idle, and load using Prime95 (large FFTs setting) and FurMark, an OpenGL
benchmarking and stability testing utility. This puts more demand on the CPU and GPU than any real life application. Throughout testing, system temperatures, noise levels, and power consumption are recorded. During the load test, the system and GPU fans speeds are adjusted to various levels in an attempt to find an optimal balance between cooling and noise while maintaining a GPU temperature of 80°C (assuming an ambient temperature of 22°C).

Baseline Noise

For our baseline noise tests, the system is left idle, the CPU fan is set to its minimum speed under PWM control (400 RPM), and the GPU fans are off by default. The system fans are connected to controllable fan headers and are set to a variety of speeds using SpeedFan. This gives us a good idea of what the stock fans sound like at different speeds with minimal interference from other sources.

Baseline Noise Level
(Idle, CPU fan at 400 RPM, GPU fans off)
Fan Speed Setting
Avg. Fan Speed
SPL @1m
16 dBA
480 RPM
17 dBA
630 RPM
18 dBA
780 RPM
20~21 dBA
910 RPM
22~23 dBA
Measuring mic positioned 1m at diagonal angle left/front
of case.
Ambient noise level: 10~11 dBA@1m.

The Define S ships with two identical 140 mm 3-pin fans, one at the back and one at the front, with a specified speed of 1000 RPM. The fans included with our sample are slightly slower, topping out at just over an average of 910 RPM, so even at maximum speed, the Define S is less noisy than most cases out of the box, outputting only 22~23 dBA@1m with our idling test system. The fans can run quieter of course but will require some form of fan control as the case lacks the R5’s built-in controller.

While the include fans are identical models, the front sample emits a faint buzzing sound that increases in pitch with speed, while the rear fan buzzes less and generates a slight rattle that is only audible from behind the case. Other than that, both have fairly good acoustics, sounding mostly smooth throughout their range.

Unfortunately, the case’s vertical hard drive mounting scheme doesn’t handle vibration very well, as indicated by a strong tone being generated at 120 Hz, corresponding to our SSHD’s 7200 RPM motor speed. While the drive is isolated with grommets, it hangs on its side without any additional physical support, shaking the motherboard tray. When a vibration issue like this crops up I attempt basic modifications to see if there’s a simple way of remedy the situation, but the unorthodox design makes these methods ineffective. There’s no easy way to brace the drive sufficiently to reduce this effect.


System Measurements (80°C Target GPU Temp)
System State
CPU + GPU Load
CPU Fan Speed
400 RPM (Min)
800 RPM
Avg. System Fan Speed
630 RPM
630 RPM
780 RPM
910 RPM
GPU Fan Speed*
1260 RPM
1120 RPM
1070 RPM
CPU Temp
MB Temp
GPU Temp
System Power (AC)
18 dBA
23 dBA
24 dBA
25 dBA
*set as low as possible to maintain target GPU temperature on load.
Ambient temperature: 22°C.

The results of our load tests are surprisingly linear compared to other cases. As the system fan speeds are increased, CPU and motherboard temperatures go down (the SSHD, being relatively isolated isn’t effected by anything), and noise levels go up, even though improved cooling allows the GPU fans to be slowed down. Either the 60% or 80% system fan speed level can be considered the sweet spot depending on whether cooling or noise is a priority. Personally, I’d go with the quieter 60% setting as its rare for a case to stay below the 24 dBA@1m mark with our test parameters.

On load, the higher CPU fan speed and the GPU fans turning on doesn’t affect the overall sound significantly. The video card fans increases the pitch somewhat, but the machine still sounds pleasant enough with no audible tones or other defects.

Case Comparison: System Measurements
(CPU + GPU Load, 80°C GPU Temp)
Fractal Define S
SilverStone KL05
Corsair 500R
Zalman Z11 Neo
Avg. System Fan Speed
630 RPM
(2 x 80%)
840 RPM
(2 x 60%)
810 RPM
(3 x 60%)
550 RPM
(4 x 40%)
960 RPM
(3 x 70%)
GPU Fan Speed*
1120 RPM
1070 RPM
1410 RPM
1090 RPM
1180 RPM
CPU Temp
MB Temp
System Power (AC)
23 dBA
24 dBA
24 dBA
25 dBA
25 dBA
*set as low as possible to maintain target GPU temperature.
CPU fan at 800 RPM.
Ambient temperature: 22°C.

Compared to previously tested cases around the US$100 price-point or lower, the Define S offers modest thermal performance and a slightly lower noise level, at least in its optimal fan speed configuration.


These recordings were made with a high resolution, lab quality, digital recording
system inside SPCR’s own 11 dBA ambient anechoic chamber, then converted to
LAME 128kbps encoded MP3s. We’ve listened long and hard to ensure there is no
audible degradation from the original WAV files to these MP3s. They represent
a quick snapshot of what we heard during the review.

Each recording starts with ambient noise, then 5~10 second segments of product
at various states. For the most realistic results,
set the volume so that the starting ambient level is just barely audible, then
don’t change the volume setting again while comparing all the sound files.


The Define S is an unusual alteration to the R5. A lower cost, simplified version that lacks a few nonessential features like the fan controller, extra front USB ports, and side panel locking mechanisms is understandable, but this doesn’t completely jibe with the focus on watercooling. Taking out drive cages to make room for custom loop components makes sense, but enthusiasts who pursue this line of cooling have reasonably deep pockets so cutting extras to save a mere US$30 is unnecessary. And if Fractal Design truly wanted to make a more watercooling-friendly tower, they would have also added some more room up top to allow for thicker, ceiling-mounted radiators, as that position offers more open airflow than the front. [Editor’s Note: But a real change in the height of the case would have required retooling, which is no piffling expense.]

The lack of drive support may be a problem for some, but most users don’t need more than three 3.5 inch drives, and 5.25 inch bays become less relevant with each passing day. If you do require an optical drive, a hotswap drive rack, or a memory card reader, there are many external options. The other notable 5.25 inch accessory is an aftermarket fan controller but motherboard fan control are often quite capable these days. The new drive mount scheme isn’t as secure as the R5’s traditional drive cage, making drive vibration a potential problem. If you’re sensitive to that kind of noise, it would be prudent to stay away from high RPM drives altogether.

That being said, my overall impression of the Define S is positive as it retains much of what’s good about the R5. It’s well put together, has superb cable management, and its well-ventilated design produces excellent performance with only two fans. The R5 is more versatile, but this budget version is certainly no slouch, and it’s nice to see quality ATX tower case enter the market for less than US$100.

Our thanks to Fractal Design
for the Define S case sample.

The Fractal Design Define S is Recommended by SPCR

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SilverStone Kublai KL05 Budget ATX Case

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