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 Post subject: 5 fans tested at equal airflow when mounted on an S1283 HSF
PostPosted: Fri Jun 20, 2008 9:54 pm 
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Joined: Thu Dec 15, 2005 11:06 am
Posts: 2049
Location: Klamath Falls, OR
SFL: Scythe 1200RPM nominal S-Flex, 7 blades
SS: Scythe 1200RPM nominal "M" Slipstream, 9 blades
NCB: GlobalWin NCB ceramic bearing 1300RPM nominal, 7 blades
Noc: Noctua 1300RPM nominal, 9 blades
MAG: Enermax Magma 1500RPM nominal, 9 blades

All fans are 120mm x 25.4mm ("25.4mm" is the complicated way Frenchmen spell 1"). Prop airflow sensor RPM was always 152RPM, SLM-hub distance 2.5", ambient ~30dBA. The fan voltage and RPM needed to provide 152RPM on the sensor prop are listed as well as the noise level at 2.5".

Code:
SFL 1006RPM  9.88V 36.8dBA
SS  1014RPM  6.73V 39.6dBA
NCB 1181RPM  9.86V 40.5dBA
Noc 1211RPM 10.04V 43.0dBA
MAG 1207RPM  6.98V 43.2dBA


In my earlier comparison of the SS and SFL, the S-Flex had to spin a lot faster to push the same airflow as the Slipstream. Here, with some backpressure, the two fans turn almost exactly the same RPM at the same airflow. This is why, although the SS wins in free air, SFL wins using this particular backpressure test.

Considering the NCB has been around a long time, is cheap, and has long-lasting ceramic bearings, I thought it did rather well. I've always liked that fan, and Madshrimps has adopted it as its standard fan for testing HSFs that mount 120mm fans.

Three of the fans were brand new out-of-the-box, and the other two were purchased recently and had only been tested once and not put to other use.

I've posted pics and info of the test fixture in the Silent Front forum, subject "A controlled back-Z fixture based on the HDT-S1283 HSF" if you want to know more about it.

edit: corrected "it's" to "its"


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 Post subject: A sixth fan tested; 38mm thick this time
PostPosted: Sat Jun 21, 2008 3:53 pm 
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Joined: Thu Dec 15, 2005 11:06 am
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Location: Klamath Falls, OR
Since pressure seems to be the question, I tossed my 120x38mm (Ultra Kaze??) fan, the one that's labelled 1000RPM (which is what I ordered) but turned out to be a 2000RPM, into the mix. 7 blades.

What I got was 1055RPM fan at 4.95V when at 152RPM sensor. The noise level was 39.7dBA, a tenth of a dBA worse than the Slipstream1200. I can't add it to the previous post, because the ground rules are 25.4mm fan thickness.

I liked my SilenX 120x38mm fan and its really low bearing noise. It got sacrificed in one of my experiments, but I can always get another. Interesting that it took 1055RPM on the Ultra Kaze, but only 1006RPM on the SFlexE fan, to get 152RPM on the sensor...


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PostPosted: Sat Jun 21, 2008 4:30 pm 
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Location: St Louis (county) Missouri USA
Interesting.....same results as I had when I tested a bunch of fans a while back. I had the restriction on the intake side....you have it on the exhaust side.

The S-Flex and the Slip-Stream performed virtually the same for me.....and the Noctua trailed, even though it's supposed to be designed to excel in such situations. It's going to be tough to find a fan to beat those Scythes.

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 Post subject:
PostPosted: Sat Jun 21, 2008 9:17 pm 
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Location: UK
i'm surprised by the big difference in noise level between the SFL and SS at basically the same RPM; subjectively, was it aurally obvious that the SFL was the quietest of the fans on test for this particular setup?

also this is quite a good result by the slipstream, as it's not one of those fans that's "supposed" to have good pressure ability (ie not extra thick, no trick blades).

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 Post subject:
PostPosted: Sun Jun 22, 2008 5:05 am 
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Joined: Thu Dec 15, 2005 11:06 am
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Location: Klamath Falls, OR
jaganath wrote:
i'm surprised by the big difference in noise level between the SFL and SS at basically the same RPM; subjectively, was it aurally obvious that the SFL was the quietest of the fans on test for this particular setup?

Too much time passed between different fans for my ear to "remember" the sound level with any accuracy.

I'm not surprised by the SS's noise. I've consistently questioned how well the SS would work under backpressure. Well, it depends on how much backpressure, which again is no surprise.

In free air, at the same RPM the SS would push a lot more CFM than the SFL. That they push the same in this test at essentially the same RPM means the SS blades are operating at a high angle of attack and generating acoustic turbulence.

Again: it depends on how much backpressure. These HSFs create much more backpressure than I expected. Not much air gets shoved between the fins even on the medium-impedance (for an HSF) S1283.


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