SPCR's Fan Roundup #4: 120mm Fans II

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SILENX IXTREMA PRO IXP-74-11

Ambient noise at the time of testing was 18 dBA.

Brand SilenX Power Rating 0.16A / 1.92W
Manufacturer ? Airflow Rating 43 CFM
Model Number IXP-74-11 RPM Rating 1,100 RPM
Retail Availability Yes Noise Rating 11 dBA
Bearing Type Hybrid Immersion Header Type 3-pin & Molex Adapter
Hub Size 1.29" Starting Voltage 2.5V
Frame Size 120 x 120 x 25 mm Number of Samples 2
Our thanks to Anitec Computer Technology for supplying these samples.
Voltage
Noise
RPM
CFM
Power
12V
26 dBA@1m
1140 RPM
35 CFM
2.80W
9V
22 dBA@1m
960 RPM
29 CFM
2.13W
7V
20 dBA@1m
820 RPM
25 CFM
1.72W
5V
~19 dBA@1m
660 RPM
19 CFM
1.27W
@25 CFM (7.0V)
20 dBA@1m
820 RPM
25 CFM
1.72W
May 5, 2008
The updated airflow results here are the result of improvements in our testing procedures. They are more accurate than the original results above, but they are not directly comparable. Please compare these only with fan reviews published after May 5, 2008 — or ones that have updated results published in a box like this one.
12V
26 dBA@1m
1140 RPM
35 CFM
2.80W
9V
22 dBA@1m
960 RPM
27 CFM
2.13W
7V
20 dBA@1m
820 RPM
23 CFM
1.72W
5V
~19 dBA@1m
660 RPM
19 CFM
1.27W
@20 CFM (5.6V)
20 dBA@1m
700 RPM
20 CFM
1.41W

May 5, 2008
The SilenX Ixtrema Pro was one of the few fans whose results went up when we retested all of our fans. In light of the new results, it now boasts one of the best airflow-per-rotation ratios that we've seen. It's unfortunate tendancy to resonate still hinders it, but it may be worth a second look. Please evaluate the new results carefully.

A SilenX at last. A "proper" SilenX, not an obscure 80mm model. Those of you who aren't regular readers are probably wondering what the big deal is. To summarize a very long story:

  1. A SilenX spokesman was caught shilling his product by carrying on a conversation with himself on SPCR's forums, reregistering himself several times after his fraudulent activities were exposed by SPCR staff.
  2. SilenX' specifications are notoriously exaggerated, especially where noise is concerned.
  3. Thanks to widespread distribution and aggressive marketing (see point 2.), SilenX fans have a reputation for being quiet — but not on SPCR
  4. For a very long time, in part because of point 1., SPCR had never "officially" reviewed a SilenX product.

All of this has been water under the bridge for some time, but a reputation once earned is hard to get rid of. And, every month or so, someone new asks why SPCR hasn't reviewed / approved any SilenX fans, and the whole thing gets dragged out of the mud again.

All of this is really just a very long way of saying one thing: SilenX carries baggage at SPCR. And so, by popular demand, here is an "official" SPCR look at one of SilenX' current 120mm fans.

Perhaps because SPCR has been so hard on them in the past, SilenX has gone out of their way to prove the legitimacy of their noise specifications. They are one of the very few manufacturers that specifies a measurement distance along with their noise specification: "Measurements are taken in an anechoic chamber from a distance of 1m along each of the 3 axes and a mean is calculated from the readings". We've been talking ourselves blue in the face about the importance of measurement distance, and SilenX is one of the few manufacturers that seems to have listened.

Unfortunately, while SilenX appears to be doing everything right, we still can't reconcile our 26 dBA@1m reading with SilenX' 11 dBA@1m. That's not a small difference. It's hard to write that off as measurement variance, even allowing for the fact that SPCR doesn't have access to an ultra-quiet anechoic chamber. Given how far above ambient our own measurement is, SilenX' 11 dBA noise spec just doesn't wash.

Quibbles with specifications aside, the SilenX doesn't sound too bad. It's probably smooth enough for most casual users, though enthusiasts will be less pleased. The fancy "metallic" plastic used for the frame may look flashy, but it's terrible for sound. Lightweight and brittle, the material picks up fan vibration easily and audibly, giving the fan a highly resonant character. At slower speeds, the resonance manifests itself as a deep buzz or growl, while at higher speeds it's more like a pure tone. The resonance prevents what is an otherwise low-noise fan from ever becoming truly inaudible, even at 5V.


Silicone grommets to help control vibration resonance.

It's unfortunate that SilenX chose such a poor quality material, since they've done several other things right. Most significantly, the retail package comes with four silicone grommets that are intended to deal with the issue just raised: Resonance. Such grommets can help prevent the transfer of vibration to the case, but they do nothing for the resonance in the fan itself.

It's also worth pointing out that SilenX has made an effort to force as much airflow as possible out of the Ixtrema Pro. The center hub is unusually small, apparently "for reduced air turbulence" and to allow slightly more air to pass through the frame. As a result, the fan blades appear unusually long and scooped. SilenX' marketing material claims that this gives the fan better pressure characteristics, but how much so is difficult to say. Our airflow measurements did not uncover anything particularly special about the Ixtrema Pro's airflow characteristics... but we are unable to measure the effects of pressure.

All in all, the Ixtrema Pro is an interesting fan that may be worth experimenting with. Although it's noise character is not perfect, it may be good enough to work with while learning about what kind of airflow is produced by its unusual blade design.

Noise Recording

ARCTIC COOLING ARCTIC FAN 12L

Ambient noise at the time of testing was 18 dBA.

Brand Arctic Cooling Power Rating 0.15A
Manufacturer Arctic Cooling? Airflow Rating 37 CFM
Model Number Arctic Fan 12L RPM Rating 1,000 RPM
Retail Availability Yes Noise Rating 20.0 dBA / 0.3 Sone
Bearing Type FDB Header Type 3-pin
Hub Size 1.85" Starting Voltage 5.3V
Frame Size 120 x 120 x 25 mm Number of Samples 3
Voltage
Noise
RPM
CFM
Power
12V
23 dBA@1m
1040 RPM
28 CFM
0.61W
9V
20 dBA@1m
820 RPM
20 CFM
0.49W
7V
~18 dBA@1m
650 RPM
17 CFM
0.41W
5V
<18 dBA@1m
480 RPM
11 CFM
0.35W
@25 CFM (11.0V)
21 dBA@1m
970 RPM
25 CFM
0.57W
May 5, 2008
The updated airflow results here are the result of improvements in our testing procedures. They are more accurate than the original results above, but they are not directly comparable. Please compare these only with fan reviews published after May 5, 2008 — or ones that have updated results published in a box like this one.
12V
23 dBA@1m
1040 RPM
26 CFM
0.61W
9V
20 dBA@1m
820 RPM
21 CFM
0.49W
7V
~18 dBA@1m
650 RPM
16 CFM
0.41W
5V
<18 dBA@1m
480 RPM
10 CFM
0.35W
@20 CFM (8.8V)
20 dBA@1m
810 RPM
20 CFM
0.47W

May 5, 2008
The questionable airflow results for Arctic Cooling's fans was one of the major reason for developing our new methodology. We are now much more confident in the results for this fan — and its results move it up in the rankings as well. Unfortunately, the change only brings it up to the middle of the pack — it's still not one of our favorite fans. Questions about its ability to provide good air pressure remain.

Arctic Cooling has established itself as a tough little company with a reputation for engineering inexpensive but elegant products. They were one of the first companies to take noise seriously as a design issue, and some of their past products have become favorites on SPCR.

Arctic Cooling has been experimenting with "frameless" fans for a long while — first on their heatsinks, and then later as independent models. The idea is to reduce air turbulence (and its corresponding noise), and, in general, Arctic Cooling has done a good job of making quiet fans in the past.

The most recent incarnation of these fans retains the open design and adds silicone grommets that are intended to reduce the amount of vibration conducted through the frame to the case. The motor assembly and the frame are actually separate pieces, held together by four silicone mounting posts. The silicone is soft and pliable, and should do an excellent job of reducing vibration.


The entire motor assembly is soft-mounted with silicone grommets.

Measuring the Arctic Fan 12L fairly was a challenge; its unconventional design caused serious issues with our original technique for measuring airflow. In fact, the fan's unusual characteristics were a factor in our recent decision to update our airflow testing methodology, as our previous technique produced results that were unrealistically low. Our new system of measurement brought the Arctic Fan 12L back in line with our expectations, though it still seemed to produce slightly less airflow overall. However, the difference was no more than 5~10% — not enough to worry about from a thermal perspective.

The small disadvantage in airflow proved to be a larger disadvantage when the fan was compared to other fans at 25 CFM. That 5~10% difference was enough to make the Arctic Fan 12L clearly audible at 25 CFM where other fans managed to disappear, since the Arctic Fan had to spin faster to produce the same amount of airflow. Were it not for this disadvantage, the Arctic Fan would be worthy of recommendation, but unfortunately, it doesn't quite keep up.

The noise character was a low growling hum that got smoother as the fan speeded up. The fan was inaudible from a distance of one meter below about 6V, but moving closer the sound became clearly audible and was quite rough-sounding. Above this level, the noise became smoother and more pleasant to listen to, but it also increased in volume. It was difficult to find a balance between low volume and good noise character.

The silicone grommets surprised us in that they didn't seem to do much to stop vibration. In fact, the Arctic Fan had more vibration that most of the other fans. Ironically, this is likely a result of the frameless design. Generally, fans with heavy, solid frames exhibit less vibration because they have more inertia to resist motion. With such a lightweight frame, the Arctic Fan literally hummed with motion, the grommets moving along with everything else. It's possible the fan would perform better when hard-mounted to a solid case, but our free-air tests weren't encouraging.

Noise Recording

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