Fractal Design Define S Case Review

Designed for liquid-cooling enthusiasts, Fractal Design’s Define S could be the perfect solution for your next extreme cooling build.

“Extreme” system builders are known for chopping away at their cases to fit more stuff inside, typically ditching entire drive cages and sealing off external bays in order to create more mounting space and a “cleaner” look. Fractal Design takes the concept a step further by eliminating those parts from the entire design of its Define S, while maintaining the sturdy shell upon which the company has built its reputation among some of these same enthusiasts.

The best part might be that Fractal Design isn’t charging you to modify an existing case, but has instead deducted the cost of bays and cages from the price of a new model. Weighing in at a fairly hefty 18.2 pounds even without the weight of cages, the Define S sells for around $70.



Before we open the Define S to reveal its variety of internal liquid cooling support features, let’s take a closer look around the outside.

Fractal Design replaced its classic noise-dampened door with a similar-looking solid face panel, above which are two USB 3.0 ports, power and reset buttons, plus headphone and microphone jacks. Removable outer covers behind those ports allow full access to the internal top panel.

Because it’s designed for lots of internal liquid cooling hardware, Fractal Design saw no need to put port holes for liquid coolers on the back of the Define S. We don’t consider that a weakness, though we would have preferred to see eight expansion slots rather than the seven provided.

A magnetic front and slide-in bottom dust cover protect all “intake” positions, including one optional bottom fan mount, three front fan mounts, and a power supply inlet.


Other than its durable steel sheetwork, Fractal Design is also known for its liberal application of cloth-faced asphalt damping sheets. The Define S’ plethora of vents combine with its left side window to leave only the right panel with enough space for proper application of these sheets. This may not be the most effective location to focus its noise-reduction efforts, but it is the most practical.

Inside, we find a front panel support for triple-120mm radiators (we refuse to call these 360mm because they’re 120mm wide), in addition to wider dual-140mm units (280x140mm spacing).

There’s around 17.8” of card space as well, which gets reduced by the thickness of any fans and/or radiators added to the front panel. That doesn’t mean we can install an oversized motherboard, though, as the raised section at the front of the motherboard tray limits internal board depth to around 9.9”.

A look around the back of the tray shows why motherboard length is restricted to standard ATX: three 3.5” drive trays fill the forward edge of the “stow” space, and two more 2.5” trays rest directly behind the board. The larger trays are also dual-drilled for smaller units, in case you’re inclined towards five 2.5” drives.

The lack of front drive cages gave Fractal a lot of room to place screw holes and slots for various liquid cooling devices.

Fractal Design defines the Define S as having room for a “420mm” radiator, but it’s hard to see how the tanks of some 3x 140mm units will clear the case ends. Triple 120 is far easier, and both sets of mounting screws are offset away from the motherboard to allow vertical overlap without component collision.

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