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 Post subject: A quick equal-airflow comparison of slipstream, new enermaxPosted: Thu Apr 10, 2008 7:42 pm

Joined: Thu Dec 15, 2005 11:06 am
Posts: 2049
Location: Klamath Falls, OR
Units tested were an old Enermax Marathon (1 of 3 samples I have), a new Enermax Magma (1 of 2), and a new Scythe Slipstream 800 (1 of 2). The ambient noise was 27.9dBA. I selected 3" microphone distance because the Marathon was at 35.8dBA and I wanted as much distance as practical. Bad choice, the Slipstream wound up at 30.8dBA, only 3dBA higher than ambient. But this was a quick test.

The Marathon was run wide open at 12V, and I got 505sensor, 982fanRPM and 35.8dBA.

The Magma, at 12V, gave 883sensor, 1657fan, and 47.7dBA. When the voltage was turned down until I got 505sensor, 5.89V, 1006fanRPM, 34.3dBA.

The Slipstream 800 at 12V measured 510sensor! Which is why I had a Slipstream 1200 standing by. Whew! Now, 510 vs 505 is 1%. So I just barely tweaked the fan voltage and, at 505sensor I got 794fanRPM and 30.8dBA, just 3dBA above ambient.

The Slipstream - Marathon difference surprised me. The first time around, I got a 1.6dBA difference in favor of the Slipstream. But this new test was run with different fans, and the original Slipstream was a 500RPM model.

794/1006 = .789, so the Magma has 78.9% of the Slipstream's pitch, and the Slipstream has 26.7% greater pitch than the Magma.

Another datum: the "18dBA per RPM doubling" formula, applied to the two Magma measured RPMs, predicts 13.0dBA difference. I measured 13.4 - and I did the measurements before the calculation.

dBA = LOG10(rpm1/rpm2)*60 is the formula, if you forgot.

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 Post subject: Posted: Thu Apr 10, 2008 11:50 pm

Joined: Tue Sep 20, 2005 6:55 am
Posts: 5085
Location: UK
looks like a resounding victory for the Slipstream, albeit based on initial results.

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 Post subject: Posted: Fri Apr 11, 2008 2:04 am

Joined: Sat Jan 18, 2003 2:19 pm
Posts: 5316
Location: St Louis (county) Missouri USA
Well damn....I've been waiting for these new fans to show up. Looks like a big disappointment. Those Scythe Slip-Stream fans are going to be hard to beat. Thanks for all the testing.......maybe you can get some of those -db SilenX 120s and run them against the Slip-Stream.

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 Post subject: Posted: Fri Apr 11, 2008 6:20 am

Joined: Thu Dec 15, 2005 11:06 am
Posts: 2049
Location: Klamath Falls, OR
jaganath wrote:
looks like a resounding victory for the Slipstream, albeit based on initial results.

I agree. It also looks as if the 800RPM model is quieter than the 500 at equal airflow - something I'm gonna have to test.

I've got lotsa testing lined up - I now have (still in their boxes) unused samples of the Enermax Cluster 1200RPM PWM, the Scythe 1200RPM PWM, and the Arctic Cooling 1500RPM PWM fan. Today I plan to test these as PWM fans, not as 3-pin fans as I previously tested the Scythe and A-C.

I think I can mathematically show why the Slipstreams are so darn quiet. When I get around to writing that up, I'll post it in The Silent Front forum. I'd naturally expect everyone to accept my argument without argument (cough).

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 Post subject: Posted: Fri Apr 11, 2008 6:25 am

Joined: Thu Dec 15, 2005 11:06 am
Posts: 2049
Location: Klamath Falls, OR
Bluefront wrote:
Well damn....I've been waiting for these new fans to show up. Looks like a big disappointment. Those Scythe Slip-Stream fans are going to be hard to beat. Thanks for all the testing.......maybe you can get some of those -db SilenX 120s and run them against the Slip-Stream.

Thinking of you, Bluefront, and your need for higher RPM fans for use with filters, I plan to test the 1200RPM Slipstream against the 1500RPM Magma. Should provide about equal airflows. I predict the Slipstream will win big, but measured data is preferable to guesses...

edit: I did run the SilenX 120 against the Slipstream500 in that big initial roundup, as I recall. The X finished in the middle of the pack as I recall.

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