Case fans are probably the equalent of the cubby holes that feature in many cars. They are not a deal breaker, until you need them. Once you do, you begin cursing yourself for not paying attention before making the purchase. No one really thinks of case fans when buying a new computer. It is only afterwards, when the noise or their lack of ability to keep your heat guzzling computer cool, do you start to feel the “pain” of not paying much attention before. This is where case fan reviews come in. No one is really going to read them, until it is already too late. Better late than never I always say! Today we are going to review two case fans from Noctua. The NF-S12B FLX is a 120mm fan and the NF-P14 FLX which as the name suggests is a 140mm fan.

A CLOSER LOOK AT THE FANS

Both the fans are boxed in the all too familiar Noctua style. They follow the same color scheme and design as all Noctua products. This is essentially not a bad thing, as it becomes easy to spot them when shopping around. Think of it as looking for the familiar Pepsi colors in a cooler full of a dozen brands

The front of both the boxes highlight the major features of the fans along with a transparent window that gives you an insight to the hardware itself.

The back side of the packaging gives some more details on these features as well as a brief description of the product in six different languages. You can also find a small table listing some of the specifications on these fans.

There is an inlay at the back which is stuck on to the it by Velcro. The inlay describes some of the specific design improvements.

Inside the box, you will find the fan and the connectors neatly arranged in a plastic tray.

The fans ship with three different adapter cables which allow three different speeds of operation at different noise levels. You also get four metal screws and four rubber plugs for vibration compensation in case you don’t want to attach the fans with the metal screws. As with the packing, the fans are in traditional Noctua colors as well. No snazzy “greens” or “orange” or UV reactive shells here. And there are no LED lights either. Noctua seems to place a lot of importance on functionality rather than looks. Remember why you are reading this article? How your current fans are just no good? Now see it from Noctua’s perspective about putting functionality first.

REINVENTING THE FAN

So how does Noctua actually improve the functionality of their fans? They do so by modifying the Stator and Rotor design (of their fans). The Stator is the term used for the static components of the fan, while Rotor refers to those parts that rotate. Generally speaking an ideal fan should be able to keep your computer cool and at the same time generate no noise at all. To get as close to the ideal as possible it is necessary to modify the “generic” fan design –to reinvent the fan.

COMMON DESIGN CHARACTERISTICS

The common features among the two fans are described first. Specific modifications that apply to either the NF-S12B or the NF-P14 are described afterwards.

FAN ROTATION SPEED

The faster the fan turns the more noise it makes. In order to control the fan speed, Noctua provide speed control adapters with their fans. The Ultra Low Noise Adapter (ULNA) and Low Noise Adapter (LNA) reduce fan noise by reducing its rotational speed. This is called the “FLX” (flexibility) system by Noctua. From the default 1200 rpm, the LNA reduces the speed to 900 rpm, while ULNA reduces it to 600 rpm. (750 rpm for the NF-P14).

NOISE FROM THE MOTOR

DC motors use a commutator switch to produce a steady torque or rotating force. Within the commutator the electrical current reverses direction. If this reversal is abrupt, the change in torque is abrupt as well which leads to greater noise generation. If the change in reversal of current is smoothed out, so is the change in torque which results in lower noise levels Noctua calls this the Smooth Commutation Drive Rev-2 or SCD2 for short. The applied principal is the same as outlined above.

NOISE FROM FRICTION

Bearings are used in motors to allow for a constrained motion. Depending on the type of bearing used varying degree of friction and noise is generated . Noctua employs a type of fluid bearing which it calls the Self Stabilizing Oil Pressure (SSO) bearing. Computer fans generally employ either sleeve or ball bearings. The former provides for quiet operation, but longevity is affected. The latter allows for a longer fan life, but the noise generated is more as compared to the sleeve bearing. The SSO bearing brings the best of both worlds to the table. The low noise of the sleeve bearing, coupled with the reliability of the ball bearing.

NF-S12B FLX DESIGN CHARACTERISTICS

IMPROVING THE BLADE DESIGN

Case fans usually feature blades that are “straight”. This allows for maximal airflow, but also generates a lot of noise. To lower the noise levels, without sacrificing the airflow Noctua modified their blade design by making two critical changes to it. Before going into those changes, a little science lesson:

BLADE LEADING EDGE

The leading edge is the part of the blade where the air first comes in contact with it. This part divides the air into two streams; one passes above, the other below the blade [I]BLADE TRAILING EDGE[/I] The trailing edge is the rear part of the blade where the air streams rejoin after being separated at the leading edge

Increase the size of the bladeTo increase the size of the blade the tip clearance (the distance between the blades and the frame of the fan) has to be reduced. This is done by increasing the length of the “leading edge” of the fan blade. Not only does the reduced tip clearance increase the size and surface air of the blade, it also generates extra noise. The second design change deals specifically with noise levels

Bevelled blade tips

The tip of the blade features beveling at the trailing edge. The trailing edge of the blade is the part where the blades have the maximal velocity, which implies maximal noise generation. Beveling helps reduce the interaction between the frame of the fan and the blades in order to reduce the noise.

The picture shows the actual bevelled design on the fan's blade. These two changes help improve the airflow to noise ratio by up to 10% as per Noctua’s testing.

NF-P14 FLX DESIGN CHARACTERISTICS

IMPROVING THE BLADE DESIGN

The NF-P14 features a 140mm rotor (or impeller). The blades have specialized notches on the trailing edge called the “Vortex Control Notches” or VCN for short. Remember that it is the trailing edge where the two streams of air that were separated at the leading edge combine. This recombination causes noise generation. To reduce the impact of, the trailing edge features the VCN. These help to divide the air-flow into several small streams, rather than one combined stream and leads to lower noise generation.

IMPROVING AIR FLOW

Large fans (larger than 120mm) usually tend to suffer from low static pressure. To over come this, the Noctua NF-P14 employs a 9 blade rotor (impeller). This allows the fan to be used not only as a case fan, but as a fan on a processor cooler or radiators.

IMPROVING STABILITY

The motor hub and the bearing shell are all made of metal. This is to ensure stability of the large 140mm rotor.

IMPROVING COMPATIBILTY

The fan can be mounted in a 120mm or a 140mm aperture. The fan is thus a drop in replacement for 120mm fans as well as providing mounting option for a 140mm opening.

OFFICIAL SPECS

TESTING

The fans were tested in two different systems.

TEST SYSTEM 1

TEST SYSTEM 2

The ambient temperature for both tests was 20°C. The fans were connected directly, without noise control cables to adjudge maximum cooling performance.

SYSTEM 1

As you can the processor’s temperatures are more affected as fans are added as compared to the board temperature which more or less stayed within a couple of degrees. Remember that the case had its default fans installed during testing

SYSTEM 2

For system 2, the board temperature was replaced by the Northbridge temperature, which is the hottest component. The most remarkable difference is seen in the processor temperature as fans are added. The difference between “No” fans to “Two” fans is 5°C. The Northbridge temperature is pretty stubborn and stays around the same at idle and load.

NOISE LEVELS

The fans were tested with speed control adapters to see speed-noise relationship

Naturally the NF-S12B with ULNA generates the lowest noise. Both fans running at full speed generate the most noise.

CONCLUSION

These fans come into their own when pitched against a “hot” system. The Core i7-920 (at 3.6 GHz) saw the most dramatic temperature improvements. As I said at the beginning, the reason you are reading this is probably because your system is over-heating and you need a way to cool it down. If that is the reason, the solution has been presented. Noctua fans get the job done without deafness inducing noise.

PROS

Solid fan construction Fan speed control cables Anti-vibration plugs Excellent cooling dynamics Low noise

CONS

No LEDs Fan control cables substituted for a controller