Cooler Master has brought to market their “Fourth Generation Bearing,” a bearing based on POM (polyoxymethylene). So far, they have built three fans with POM bearings. The second fan to use a POM bearing is the Jetflo, the very fan we will be reviewing here. The Jetflo has a number of features that make it an interesting fan indeed. In fact, the POM bearing is just the first of its features. So let us review them all, and put the fan through its paces.
Features and Specifications
The Cooler Master Jetflo is a PWM fan that ranges from 800 to 2000 RPM, with a stated output of 95 CFM. It comes in four flavors: red, white and blue LEDs and no LEDs. The Jetflo also comes with two adapters that allow fixed speeds at 1200 and 1600 RPM. The POM bearing is rated to 160,000 hours, or more than 18 years. Cooler Master tells us that the fan’s blades focus its airflow instead of spreading it out as normal fans do.
One of the features Cooler Master does not tell you about is the fact that the corners are rubber pieces that are bolted onto the fan’s frame. This feature is designed to cut down on fan vibrations, so they are not transmitted to what it is attached to.
Cooler Master Jetflo Specifications (from product page)
|Model||R4-JFNP-20PK-R1 (No LED)|
R4-JFDP-20PB-R1 (Blue LED)
R4-JFDP-20PR-R1 (Red LED)
R4-JFDP-20PW-R1 (White LED)
|LED Color||Red / Blue / White / Dark (No LED)|
|Dimension||4.7 x 4.7 x 1 inch|
120 x 120 x 25 mm
|Fan Speed||800-2000 RPM (PWM) ± 10%;|
w/ silent adapter: 1600/1200 RPM (fixed)
|Air Flow (CFM)||95 CFM ± 10%|
|Air pressure (mmH2O)||2.72 mmH2O ± 10%|
|Life Expectation||160,000 hrs|
|Noise Level||19 dBA (1200 RPM with included silent mode adapter)28 dBA (1600 RPM with included silent mode adapter)36 dBA (without silent mode adapter)|
|Bearing Type||POM Bearing – CM 4th Gen. Bearing|
|Accessories||Silent mode adapter x 2|
(1600 RPM x 1, 1200 RPM x 1)Metal screw x 4
Package and Contents
The Cooler Master Jetflo comes in a fully recyclable box, with a cardboard (and recyclable) insert holding the fan and its accessories.
The box has a fold-out cover that explains various features and gives you a peek at the important elements of the Jetflo that’s inside the box.
Pulling it all out, we have a PWM Jetflo and its accessories. Note that the fan was manufactured in June, 2013. Cooler Master has been stamping manufacture dates on their fans at least back to 2008 (I have a Sickle Flow made on 2008-07-01, for example).
The accessories: two black, sleeved, well-labeled “Silent Mode Adapters” and four machine screws. What? Not the short sheet metal screws that come with most fans? These look like they should fit into nuts. But look inside the ears of the fan and you will see machine threads waiting for these screws. Note that the threads are covered with rubber, so when you fasten it to a case, there will be no metal-to-metal contact.
The adapters, by the way, carry no PWM line. So when you connect the fans in a Silent Mode they will no longer be PWM fans. Note each label carries the RPM and sound pressure level specs for that adapter.
Cooler Master Jetflo fans have rubber corners. On the output side, these are beveled up from the frame so that they hold the frame clear of any flat surface it is screwed onto. On the input side, the threaded inserts are pushed out enough to also keep the fan clear. This serves the purpose of isolating the vibration of the fan from whatever surface it is screwed to.
A closeup of one of the corners, removed from the frame. You can see the asymmetrical shape. Another aspect is that the screw hole passes clear through the ear, and allows a long 8-24 machine screw to pass right through (this is how I fasten them to the test box). I also tested m4 screws. They passed right through the corners. That makes this fan suitable for radiators.
You can also put this vibration isolator through the hole. It is the best vibration isolator I have used, and it comes stock with several fans. The embedded threads hold it firmly enough that it takes a brisk tug to pull it free.
These fans were tested in open air with a sound pressure meter (Tenma 72-942) 10 cm from the intake face of the fan. The SPL is then adjusted to 1 meter by subtracting 20 dB. The open-air RPM was also recorded and abbreviated below as FRPM (Free-air RPM).
The airflow was measured with an Extech AN100 anemometer in a custom box that has a 115 mm exit. The RPM was recorded before and after the 72 mm vane wheel was introduced into the airflow exiting the box (RPM0 and RPM). The AN100 has the capability of averaging measurements. Each CFM result is the mean of ten measurements.
For an additional treat, the airflow measures were repeated with a screen filter covering the fan to give you an idea of what each fan can do while drawing through a filter.
Note the picture below shows how the fan frame is kept clear of contacting the surface it is attached to. You can also see the 8-24 screws pushing through the corners and holding the fan with wing nuts.
Cooler Master Provided six Jetflo fans for testing. They were assessed at 12 Volts, with the 1600 RPM Silent Mode Adapter, the 1200 RPM Silent Mode Adapter, 7 Volts and 5 Volts. That sounds like essentially thirty fans and settings. But there were five CFM, SPL or RPM measurements per fan / setting, not to mention the Sickle Flow and Sickle Flow X measurements, which took the number of data points up around 150. Whew!
Seven Volts were produced by connecting the 12v and the 5v lines. However, this prevented the fans from reporting their RPM’s, so you will see those speeds marked as ‘-na-’.
Results of Testing Jetflo Fans
You see the results in the tables below. Boiled down, in performance Cooler Master under-promised and over-delivered, always a nice thing to find. Heck, behind a filter the Jetflos produced as much CFM as Cooler Master promised in free air.
When the 1600 and 1200 RPM Silent Mode Adapters are plugged in, the fans are a little louder than specified. On the other hand, they also ran faster than specified
We see an interesting Jetflo behavior when the fan is moved from free air to the test box, and the anemometer is placed over the outflow: the Jetflos speed up. They go even faster when they are pulling against the filter, but they slow down a trifle when the anemometer head is stuck into the outflow.
What you do not see in these charts is variability. Without a filter, the Jetflo’s low output was represented by a single fan at 111 CFM. The High output was a single fan at 121 CFM. The other four fans ranged from 115.8 to 116.8 CFM – essentially identical. With a filter the fans ranged from 93.43 CFM (two fans) to 97.77 CFM (two fans ran above 97 CFM). This represented tight clustering of output.
The next Jetflo aspect I investigated is the PWM curve. Now here I tested a single fan – the blue LED fan. I set my motherboard to send a PWM signal to the fan, expressed as PWM Duty, or the percent of time it is signaling. The Jetflo does not run at 0% PWM duty. It stirs to life around 10% and the speed can be read by the motherboard at 13% PWM duty.
The Speed vs PWM curve is fairly flat, once the fan speed can be measured at 590 RPM. One other important note: the fans did not click in PWM mode.
The last item I tested was the rubber corners. I tested them by putting the side of the frame directly on the metal surface of my table saw. Like most fans, it resonated and the buzzed fairly loudly. I then put a corner down. I hardly heard anything. While this was a qualitative test, it did show that the rubber corners did their job. They really did their job.
Cooler Master calls their POM bearing a “Fourth Generation” bearing. After the Sickle Flow X, the Jetflo has what I am tempted to call the second generation of their POM bearing. Can something be the second generation of a fourth generation?
The rubber corners work well to isolate a Jetflo’s vibrations from whatever it is attached to. Even better: under PWM control these fans did not click.
Although I lack the equipment to measure static pressure, I believe their specs on these, given how hard they pull through the dust filter. As for the blade shape focusing the air output, we will have to take their word for it.
As I noted above, Cooler Master under-promised and over-delivered on these Jetflos. They are good, strong fans.
- PWM control
- No PWM clicking
- Comes with two “Silent Mode” Adapters
- Jetflo fans come in four LED varieties: Red, Blue, White and unlit
- Airflow output exceeds spec
- Airflow output meets free-air spec when pulling air through a filter
- Rubber corners do a good job in stopping vibrations
- Screw holes use special screws for strong connections
- Screw holes pass through to allow connecting the fans to radiators
- At reduced speeds, the fans are not quite as quiet as advertised
– ehume (Ed Hume)