Fractal Design’s Define S case reviewed

Fractal Design’s Define R5 is my favorite case in TR’s labs right now. It’s quiet, it cools well, and it’s a breeze to work in. It’s also one of the rare cases we’ve deemed worthy of our Editor’s Choice award. At $110 and up, however, it’s positioned toward the high end of the mid-tower case market, and some buyers might not need all of the bells and whistles, or storage space, that the R5 offers.

Fractal Design appears to agree with this view. The Define S, the latest addition to the Define series, is a somewhat stripped-down—and more affordable—version of the R5. Fractal has taken a scalpel to some of that case’s extras to get the price down, but it’s kept a lot of what made the R5 so good—and it’s given the Define S a couple of new tricks inside.

Looking at the Define R5 and Define S side-by-side, one could be forgiven for having a hard time telling the two apart. The visual differences are subtle. The S’s front panel is a stealthy black plastic with a simulated brushed-metal finish. It feels decent, if a bit cheaper than the R5’s foam-lined door. The window on the Define S extends for the whole length of the side panel, all the better for showing off the system inside. Fractal removed the noise-dampening foam from this panel, likely due to the increased window area, but the right side panel is still dampened.

Behind the front panel, there’s a full-height magnetic dust filter for the three adjustable 120-mm or 140-mm fan mounts. Radiators as large as 360 mm can be mounted here, as well. Fractal has expunged all traces of 5.25″ bays from the Define S, and I’m 100% OK with that. Buyers who still need an optical drive will have to resort to an external unit, though.

Up top, Fractal carries over its excellent ModuVent system. These three foam-backed plastic panels can pop off as needed to reveal mounts for radiators or fans. When left in place, they serve to dampen system noise. Three 120-mm or 140-mm fans can be installed underneath the top panel with the ModuVents removed, as well as a radiator up to 420 mm long.

The I/O cluster features a big, round power button flanked by a reset button, headphone and mic jacks, and a pair of USB 3.0 ports.

Moving around back, the subtle differences continue. The Define S’s rear wall isn’t perforated at all save for the fan grille, and it loses the R5’s adjustable rear fan mount. That’s a bit of a shame. One of the little delights of the Define R5 came when I was able to reposition its rear fan to avoid interference from a top-mounted radiator.

The bottom of the case holds a dust filter for the power supply and the bottom fan mount. This filter pulls out from behind the case, which is rather inconvenient. The Define R5’s filter pulls out from the front, and it’s much easier to work with.  Four thick rubber feet isolate the case from floors or desktops.

Here’s a table of specs for the Define S, for easy cross-referencing with our other case reviews:

  Fractal Design Define S
Dimensions (W x H x D) 9.2″ x 17.8″ x 20.5″  (233 x 451 x 520 mm)
Supported motherboards Mini-ITX, microATX, ATX
3.5″ drive mounts 3
2.5″ drive mounts 5 (3 2.5″ or 3.5″ combo sleds, 2 dedicated)
Fan mounts 8 (windowed), 9 (non-windowed)
Included Fans 1x Fractal Design Dynamic GP14 140-mm front intake

1x Fractal Design Dynamic GP14 140-mm rear exhaust

Front panel I/O 2x USB 3.0



Max. graphics card length 16.7″ (425 mm)
Max. CPU cooler height 7″ (180 mm)
Gap behind motherboard 0.8″-1.6″ (20.3 mm-40.6 mm)

The Define S is down five 3.5″ drive mounts versus the R5, though the S’s three 3.5″ and two 2.5″ mounting sleds should be more than enough storage room for the average system builder these days. Those who need more storage will have to step up to the Define R5 or look elsewhere, though. The Define S also loses the R5’s three-header manual fan controller, but that’s another perk I doubt most will miss.

The net result of Fractal’s scalpel-wielding is a lower price point. The windowed Define S that I’m looking at today will run you $85 on Newegg right now, down from the $90 list price, while the non-windowed version is $10 less.

When the R5 and the S are both selling at full price, there’s a $30-$40 gulf between them, but since the R5 is also on discount right now, the difference is closer to $15-$25. That small of a step up muddies the Define S’s value proposition, though discounts do come and go. If you’re stuck between the two cases, it might be worth keeping an eye on the prices.

Now, let’s pull off those side panels and take a look at Fractal’s vision for the future of PC cases.


Look, ma, no drive cages

The Define S is strikingly different inside compared to any other ATX mid-tower I’ve used. The main chamber is completely open from front to back, with no provisions for storage devices of any kind. Cutting out the drive cages seems mostly like a cost-cutting measure, but Fractal uses the space freed up this way to make some interesting provisions for custom liquid-cooling setups.

The sheet metal in front of the motherboard tray, where drive cages would typically go, is instead perforated with groups of pegboard-like holes. These holes can be used to mount a liquid-cooling pump or reservoir using a set of included brackets. The open design could benefit air-cooled builds, too: airflow from the front fan mounts has an unobstructed path to the rest of the system. Out of the box, a single Fractal Design Dynamic GP14 140-mm fan blows air into the case, and another at the rear handles exhaust duties.

The motherboard tray of the Define S is inset like its fancier sibling’s, though it’s not as complicated a stamping. I really like this design, since it makes room for taller tower-style air coolers without making the case itself wider. A ring of large rubber grommets surrounds the tray for clean cable routing.

Here’s the Define S’s party trick: Fractal puts three 2.5″ or 3.5″ combo sleds behind the pegboard area, plus another pair of 2.5″ sleds behind the motherboard tray. This design makes perfect sense, but I’m curious to see what effect it has on drive temperatures, since there’s no direct airflow to any of the storage mounts—just some vent holes in the front panel of the case.

This is also all the room you get for storage. There’s no way to add drive cages to the main chamber without some custom work. Be careful about adding too many 3.5″ hard drives into your cart if you’re building a system around the Define S.

Fractal includes its trademark hook-and-loop cable straps behind the motherboard, but room for cable routing here is rather sparse compared to the Define R5’s generous 1.5″ all-around. In the 3.5″ drive area, there’s about 1.6″ (40 mm) of cable space, but directly behind the motherboard, clearances fall to about 0.8″ (20 mm). Most cables should be able to run through the roomier drive area, so the tight clearances might not be a problem in practice. We’ll see in a moment.

Popping out the ModuVents up top reveals a series of offset fan and radiator mounts. The offset design leaves two inches (50 mm) between the motherboard tray and a 140-mm radiator, while 120-mm heat exchangers clear the tray by 2.8″ (70 mm). Fractal cautions that 140-mm-based radiator stacks shouldn’t exceed 2.2″ (55 mm) in thickness here, though 120-mm-based setups aren’t subject to that limitation.

On the floor of the case, there are the usual rubber mounting feet for PSUs along with another 120-mm or 140-mm fan mount. Up front are mounting points for a liquid-cooling pump. Fractal says a wide range of Laing DDC and D5-type pumps can be mounted here, but be sure to check the mount’s dimensional drawing in the manual before buying any parts.

Putting it all together

Building a system in the Define S is remarkably easy. The only way it could have gone better is if the case had put the PC together for me. Get on that, Fractal.

Without a liquid-cooling loop in the Define S, a lot of space in the main chamber goes unused. That certainly makes for a more open airflow path, but this case really cries out for a custom loop. The pegboard area and pre-drilled pump mounting holes are expressly designed to make the installation of that equipment easier.

Unfortunately, I don’t have a custom loop on my parts shelf, but I am going to test out the next-best thing. Cooler Master’s Nepton 240M fits nicely on the Define S’s top panel, and I’ve set it up as an exhaust here. After popping out a pair of ModuVents, installing the 240M was a snap. (This picture is from the Define R5, but the two cases use identical top panels.)

Storage mounting and cable routing are both effortless in this case, aside from one minor point: the inset motherboard tray doesn’t work with right-angle SATA cables, so make sure to have some regular ones on hand. The built-in hook-and-loop straps work great, and I had no problems getting the right side panel back on, even with a full complement of power and data cables running behind the motherboard.

With the Casewarmer system in place, let’s move on to cooling and noise performance testing.


Our testing methods

Here are the specifications of my test system:

Processor AMD A10-7850K
Motherboard Asus Crossblade Ranger
Memory 8GB AMD Entertainment Edition DDR3-1600
Graphics card Zotac Nvidia GeForce GTX 660 Ti AMP! Edition
Storage Kingston HyperX 120GB SSD

Samsung Spinpoint F1 750GB HDD

Power supply Cooler Master V550
CPU cooler Cooler Master Hyper D92 (air)

Cooler Master Nepton 240M (liquid)

OS Windows 8.1 Pro

Thanks to Fractal Design for the Define S, and to Asus, AMD, Kingston, Zotac, and Cooler Master for their hardware contributions, as well.

The Define S’s opponent in today’s tests is Corsair’s Obsidian 450D. I’ll be using identical coolers and radiator mounting locations in the Corsair case.

I used the following applications in my tests:

Our case test cycle consists of the following phases:

  • 10 minutes idling at the Windows desktop
  • 10 minutes running the Prime95 Small FFTs CPU torture test
  • 10 minutes running Prime95 and the Unigine Heaven GPU benchmark
  • 10 minutes of cooldown time at the Windows desktop

Cooling performance

Here are the results of my cooling tests, plotted over time:

And here are some minimum and maximum temperatures from each testing phase:

For the most part, the Define S hangs right with the Obsidian 450D in cooling performance. One case might best the other by a couple of degrees here and there, but neither one delivers a knockout on the cooling front. I’d be happy to rely on either of these cases to keep my system chilly.

The one area where the Obsidian 450D appears to be a better performer than the Define S is SSD temperatures with the Cooler Master Hyper D92 CPU cooler installed. Here, the 450D manages a seven-to-nine-degree C advantage. Strangely, that gulf doesn’t carry over to the Nepton 240M results, where the two cases pull much closer together. That makes me think my results are a bit of a fluke—we’ll have to re-test the 450D at some point to see whether those numbers remain consistent.

Noise levels

Here are the Define S’s noise levels at idle and load, along with the Obsidian 450D’s:

Subjectively, the Define S is quieter than the Obsidian 450D with an air cooler inside, probably due to the excellent numbers measured up top. At idle, and with the ModuVents installed, the case is 2-3 dBA quieter than the 450D in most areas, save for the right side. The plain plastic front panel allows more noise to escape in testing than the Define R5’s foam-backed front door, but the difference isn’t honestly that noticeable without looking at my sound meter.

Removing the Define S’s top panels to install a radiator allows more noise to escape from the top of the case at idle, putting it about even with the 450D, but it’s more polite under load.  Installing the radiator at the front of the case would probably help even more, though it might hurt GPU temperatures.

One area where the Define S stands alone is in its suppression of hard drive motor noise. I’m not sure why, but I’m betting that the thumbscrew-secured 3.5″ drive sleds dampen vibration better than the slide-in units common in other cases. In fact, the Define S is the first case I’ve tested that hasn’t buzzed at all due to sympathetic vibrations from hard drive motors. A generally quiet case is no good if it occasionally makes a piercing racket, and the Define S is consistently quiet, not just most of the time. Bravo, Fractal.

Overall, I wouldn’t mind either of these cases under my desk, but I’d give a slight edge to the better-insulated Define S. The 450D’s more open front and top panels (and its extra 140-mm fan at the front of the case) can allow more system noise to escape, and hard drive motor vibrations can cause sympathetic buzzes and rattles in the 450D, as well.

As for the Define R5, it benches a little quieter all around than either of these cases, but it suffers from hard drive buzz, too, which mars its otherwise excellent performance. Until I reviewed the Define S, this buzz was par for the course, but Fractal has set a new bar for itself here. Hopefully the Define R6 features better drive noise dampening.



With its innovative interior design, the Define S feels something like the future of PC enclosures, not just another spin on the traditional ATX mid-tower. That’s a real achievement, given the march of relatively similar-looking cases through our labs lately. It’s exciting to see a company shake up the idea of what a tower case should be.

No case is perfect, and I do have a couple tiny complaints about the Define S. I still wish Fractal would include magnetic dust filters to replace the ModuVent panels up top when they’re removed. The bottom dust filter, while appreciated, is somewhat inconvenient to remove from the rear of the case with a system inside. Some builders might not find enough room for storage in this case, and those with optical drives are completely out of luck.

Fractal Design Define S

June 2015

Those quibbles aside, the Define S is great. Its extra-spacious main chamber is a snap to work in, its cable-routing aids make clean builds easy, and its storage mounting arrangement is brilliant. The Define S also treats custom liquid-cooling loops as first-class citizens. While the Define R5 benches a little quieter than the Define S, the difference is honestly inaudible to me—and the S finally kills the sympathetic hard drive buzz that the R5 and many other cases fail to suppress.

At just $79 for the non-windowed version, the Define S is a spectacular value given its performance and builder-friendly features. For builds with only modest storage needs, the Define S is an excellent choice. It’s also the latest TR Editor’s Choice winner.

Comments closed
    • Deo Domuique
    • 7 years ago

    I got an almost similar box 29 euros. Window is not an advantage you’ve to overpay anymore neither plastic clips instead of screws. Also, my box has ventilation holes on top, not at the bottom. Its name is “Fazn Theseus Midi Tower”. PSU at the bottom, too. I’m really amazed how cool it keeps my components.

    I don’t understand what more offers this box in order to pay triple price ( 90 euros ). To be honest, I chose an extremely normal box at the beginning because I didn’t think I could get better for the money I was going to spend. Double the price… O.K.! But triple?

    Thanks to the seller guy who told me “I’ve a much better box for you for this money”.

    • LeoScott
    • 7 years ago

    Not a problem if you keep up. My SSDs don’t vibrate. MEH

    • VincentHanna
    • 7 years ago

    its only superior if you didn’t learn your multiplication tables when you were in the 1st grade.

    • superjawes
    • 7 years ago

    If we can see both side-by-side, it would be easier to learn metric 😉

    • mav451
    • 7 years ago

    I’m curious on a difference between TR and SPCR’s take on hard drive vibration.
    Per Page 3:
    [quote<]"One area where the Define S stands alone is in its suppression of hard drive motor noise. I'm not sure why, but I'm betting that the thumbscrew-secured 3.5" drive sleds dampen vibration better than the slide-in units common in other cases. In fact, the Define S is the first case I've tested that hasn't buzzed at all due to sympathetic vibrations from hard drive motors. A generally quiet case is no good if it occasionally makes a piercing racket, and the Define S is consistently quiet, not just most of the time. Bravo, Fractal."[/quote<] Contrast with SPCR's review, page 5: [quote<]"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."[/quote<] Both reviews are using 7200 RPM drives. TR - the Samsung Spinpoint F1 750GB HDD SPCR - Seagate Desktop SSHD hybrid drive - 2TB, 7200 RPM, 8GB NAND Flash, SATA 6 Gbps If I'm being frank, that there is any issue at all raised by SPCR gives me some pause as I currently have 4 HDDs (possibly getting reduced to 2, once I consolidate by older 1TB drives). Another case I've considered is the Enthoo Evolv ATX, which employs a cantilever design for drives in the main area. Not sure that's really ideal either, but it may be an effective compromise between the S or the R5.

    • vicmeister
    • 7 years ago

    I would prefer a full tower version. The clean design is perfect for an over-the-top custom water cooling build. Perhaps Fractal Design should release multiple form factors of the same case design like the Corsair Obsidian 900D, 750D and 350D.

    • Chrispy_
    • 7 years ago

    The last thing someone interested in a small case is looking for is something double-wide with a huge footprint. The Node 804 doesn’t even try to be a product that tower buyers would want.

    • thedosbox
    • 7 years ago

    The Node’s open design is not good for noise.

    • nanoflower
    • 7 years ago

    They already have the Node 804 for people that want something much smaller.

    • TwoEars
    • 7 years ago

    Fractal Design makes great cases.

    No nonsense, understated looks, perfect function, well built, easy to work in. My kind of cases.

    • moriz
    • 7 years ago

    For those who are willing to forgo drive cages, the case to beat is the NZXT S340. Unlike this case, the S340 took advantage of the lack of drive cages by drastically reducing the case’s depth.

    It would be interesting to see a direct comparison between the S340 and Define S.

    • Qrash
    • 7 years ago

    No reaason not to include both. It only takes a moment to calculate the equivalent values.

    • Freon
    • 7 years ago

    Update: Still finding cat hair in case. =\

    • Freon
    • 7 years ago

    One of us! One of us!

    • Freon
    • 7 years ago

    Air 540 should be a similar idea of having no drives in the same section as the motherboard and in the way of primary airflow. But it’s wide to fit those 5.25″ bays (and PSU) on the back side.

    Otherwise there are plenty of other alternatives that have a more traditional setup of drive bays. Countless options. CM 690 for a similar price, for instance.

    • tsk
    • 7 years ago

    Cause metric is superior, learn to use it.

    • rpjkw11
    • 7 years ago

    Not a comment on the case, but rather the review. A BIG THANKS to TR for listing INCHES for the case specs! Most reviewers only list metric, and I understand why, but why not take an extra moment to add inches? TR does!

    End of rant.

    • alloyD
    • 7 years ago

    I just finished a build for a client using the R5 and loved it. I’d like one for my self, but it’s just a touch on the pricey side and I don’t need the myriad drive bays on my daily driver (1 each SSD and HDD is plenty for me. The server is a different story).

    The Define S looks like it’ll fit the bill perfectly for what I need.

    • Chrispy_
    • 7 years ago

    100% this.
    If they’re all the internal bays they can make it 25-33% smaller. Even [url=<]full-sized ATX boards leave a vast area of wasted space toward the front of the case[/url<]. Even the fattest, dual-fan radiator couldn't hope to use even half of that space, so it's just wasteful and makes this tower bigger than it can usefully be for no reason other than "being cheaper to make that way"

    • NTMBK
    • 7 years ago

    I wonder whether you might get the best results out of this case by putting the airflow in reverse? Put a GPU radiator on the front mounts, CPU radiator on the top mounts, and a big intake fan on the rear mount- suck cool air in from the rear, and vent through the front and top.

    • 7 years ago

    “Fractal has expunged all traces of 5.25″ bays from the Define S, and I’m 100% OK with that.
    For optical i can go either way-but 5.25” bays have other uses-
    Not being able to install a hot swap bay is a no go for me…………………………………………………..

    • DrDominodog51
    • 7 years ago

    It looks good, but I bought a 550D less than a month ago. I hate the 550D, but that’s a completely different problem.

    • thedosbox
    • 7 years ago

    I’d like a microATX version.

    • thedosbox
    • 7 years ago

    Given the R5 is available (along with dozens of other cases that still have 5.25 bays), how is this a problem?

    • the
    • 7 years ago

    [url=<]This review has a disturbing lack of cats.[/url<]

    • Khali
    • 7 years ago

    Two internal bays are a must for me as well for the same reason.

    • llisandro
    • 7 years ago

    For the tiny difference in price, smart money is probably to get the R5 anyway, which will still get you the same rad options after removing the optical drive bays if you want, although SPCR’s review suggests the S has a bit better airflow than the 5 , with the redesigned front filter/grill, FWIW.

    In my mind the whole point of this is to test the market to see if anyone wants cases completely stripped of drive mounts, and that’s why it’s got more plastic but keeps the same design- they’re just asking if anyone wants something like this.

    I think a next-gen case that’s 2-3″ wider (for drives plus better cable mgmt) but 3-4″ shallower (i.e. purpose-built for a front rad but no opticals) would be pretty cool. Or even better, cut the depth by 4″, and put some drive bays with a backplane down with the PSU in a partitioned bottom section, and make the case a bit wider for cables.

    • Chrispy_
    • 7 years ago

    Corsair and Fractal have really nailed case deign from a usability standpoint, I just wish they’d use slightly higher-quality materials.

    It’s a shame to see such nicely designed kit ruined by flimsy steel and brittle plastic. It’s serviceable and functional if you treat it right but it’s hardly what I’d look for in a case.

    Given how much people spend on the rest of a PC, it would be nice to have options from these guys that cost another $50-100 but adding build quality rather than size or features. The Obsidian 450D is the pinnacle of this for me; Good looking but the first of the Obsidian range to feel cheap and flimsy.

    • CheetoPet
    • 7 years ago

    I like the lack of internal bays, makes me happy. Be nice if they could shrink the size a bit though.

    • appaws
    • 7 years ago

    I just got one of these and moved my stuff over into it, adding a new AX360 rad in the front.

    My only complaint is that it is a little tight in back behind the mobo. An extra inch back there would be perfect.

    I also would not mind seeing something like this, but as sort of a dual chamber design like the Corsair Air 540….so I can get the PSU and tons of wiring in the back. Just make the part behind the motherboard deep enough for a PSU turned on its side.

    • derFunkenstein
    • 7 years ago

    This is a case for a very specific kind of system builder. Multiple radiators for CPU, maybe two GPUs. Something along those lines. And for that kind of builder, this is probably 100% on the button perfect. The Define R4 under my desk (and now the R5) is for everyone else that wants a full ATX system. Lots of drive bays, still a lot of bigger fans, still really quiet and good thermal performance. The Define S will probably not sell as many units, but it’s still got its place. Given how much metal they’re not using I can see why it’s cheaper, but I think they could also go the “halo” route and make a Define S-type case with all the bells and whistles and sell it at a premium, too.

    I’m happy with my case, but I’m glad this is an option, because AIO water cooling is less and less “the future” and more and more “the present”.

    • anotherengineer
    • 7 years ago

    “Fractal has expunged all traces of 5.25″ bays from the Define S, and I’m 100% OK with that. Buyers who still need an optical drive will have to resort to an external unit, though.”

    I’m not, I have an internal card reader and bluray/dvd-rw internal unit. Two 5.25″ internal bays are on my required list.

    • Khali
    • 7 years ago

    They let you play with a metal box with no drive cages and it’s an “innovative interior design”?

    If they really wanted to be innovative they would have just removed the entire area normally dedicated to the drive cages and made the case not as deep. But wait, they can’t do that because they would lose the space for mounting the hard drives on the back of the peg board.

    I think I will stick with my Corsair 600T.

    • James296
    • 7 years ago

    interesting, but I’m pretty happy with my Define R5.

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