What's the best supersize case fan?

Introduction

While other cooling products get all the limelight - we're primarily thinking of you, CPU coolers - the humble fan is just as important when it comes to cooling hardware. However, while most cases use the ubiquitous 120mm size, quite a few are now coming with supersized fans on side panels (and some other cases should come with these fans, but don't).

However, even if your case does have a massive side panel fan, it might not be much good. We've seen large fans with practically no blade-pitch - and therefore no airflow - in order to keep the case slim (and, dare we say, keep the costs down) while others have been noisy, or only just better than the practically flat fans.

Thank heavens that bit-tech is here to let know know which of these supersize fans are worth hanging on to, or what to change them for if they're not.

Once you've found the fan for you, the next question is how to mount it. In general, it's better to suck the hot air from a case as quickly as possible, so fitting the side panel fan as an exhaust would make sense. This is even more true if your graphics card has vents in the side of the cooler that pushes hot air toward the side of your case - you don't want to push that hot air back into your card's cooler, after all.

This arrangement might not suit your desk - if your case is next to your arms, you don't want it venting hot air onto you 24/7 (or maybe you do - it's your choice). Equally if your card is a little better behaved with its waste heat, you should have the side panel fan blowing inwards as it'll cool you graphics card, and your motherboard and CPU cooler. Either way, read on to see which fan is best.

How we Tested

We've scientifically measured the performance of each fan by measuring its airflow and noise. Airflow is crucial, as this figure determines how effective the fan is at moving air through your PC, while a noisy fan is an irritant everyone could do without.

Unlike most other PC components, a fan only has to perform a single task, which is to move air through your PC to help keep the components cool. Whether the fan is mounted on a CPU heatsink or radiator, blowing over the motherboard or acting as an input or output chassis fan, moving air is all that it has to do.

However, human beings are slightly more complex and demanding than your average fan. While a fan may be content with simply moving air around, we’d also like it to do this quietly. So, for this group test, we devised a method of measuring both the airflow and noise of a fan to find out which fans provide the ideal balance between the two.


Measuring airflow accurately is one of the hardest tests to perform, as the most common measuring device, the anemometer, only measures the air flowing over its surface area. This is a problem, as the velocity of the air leaving the fan will vary depending on how close the anemometer is to the centre of the fan. To measure the volume of air moved by the entire fan, not just a small proportion of it, we used the so-called ‘black sack’ method, espoused by several PC cooling hardware and air-conditioning manufacturers.

This incredibly simple device, which costs around 12p to assemble (compared to several hundred pounds for a decent anemometer) acts as a funnel that directs the airflow from a fan into a black refuse sack. The volume of the sack is a known quantity, so by timing how long it takes each fan to fill the bag with air, we can calculate the airflow using the following formula:

This tells us how many cfm (cubic feet per minute) of air the fan is moving. Using this method also allowed us to compare the airflow of fans with different diameters, simply by adjusting the size of the hole through which the fan blows air into the bag.

Obviously, the ‘black sack’ method introduces a degree of human error, which is why we tested each fan three times, and used the average time (to the nearest second) to calculate the airflow. Also, even though we used a black sack made from lightweight plastic, it was still too heavy to fill completely for the fans that have a particularly low airflow or low static air pressure, so we were unable to measure their airflow accurately. The lowest-performance fan that completely filled the sack was the Revoltec RL037, which has a calculated airflow of 7cfm; therefore, any fan that couldn’t fill the bag provided a level of airflow that was less than this.

How We Measured Noise Levels (or, More Accurately, Sound Pressure)

As few fan manufacturers state specifically how they measure sound level, it would be extremely foolish to compare the claimed figures of each manufacturer. Obviously, the only way we can really compare the sound level of each fan is by testing them in exactly the same way. For this reason, we sent all the fans to the experts at Intertek, a company that specialises in comparative testing of consumer electronic devices.

Testing was carried out in Intertek’s home-cinema listening room, which is designed to meet the IEC 286-13 standard. The measurements were taken on a calibrated Brüel & Kjær 2260 sound level meter positioned 50cm away from the intake side of the fan being tested. We chose a distance of 50cm, as this is the typical distance that most people will sit from their PCs at home.

Also, if we took the measurement from any closer than 50cm, the results would be distorted. This is incredibly important, as the further away the sound level meter is from the sound source then the lower the reading will be. The fans were powered by a passively cooled PSU, so as not to increase the sound level in the room, and held in place by two metal clamps with a reflecting surface behind.

The sound pressure level of each fan was recorded between 80Hz and 20KHz over a 10-second period. The background noise level of the room averaged 19.3dBA during the test period, although it dropped below this level several times. For this reason, any fan that measured less than 19.3dBA has been graphed with a sound level of 19.3dBA.

After testing all the fans, it can be said that any fan producing 25dBA or less was barely audible, while fans emitting between 26dBA and 30dBA were audible but not annoying. Fans measured above 31dBA were perceived to be too loud for comfort.

Not shown on the graphs, but also important, were the subjective observations we made about any particularly unpleasant noises produced by the fans. This is crucial, since the motors of some fans can produce sound at irritating frequencies, which can be very distracting, even if they’re not particularly loud.

How We Scored The Fans

Each fan has three separate scores: airflow, acoustics and value, which combine to provide the overall score.

The airflow and acoustics scores are derived from the measured airflow and noise levels of the fans, while the value score is calculated by dividing the airflow, acoustics and features score by the price. The features score takes into account the accessory bundle, awarding points for power adaptors, resistor cables, rheostats and whether the fan is mounted with traditional metal screws or anti-vibration rubber fastenings.