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.

looks like a resounding victory for the Slipstream, albeit based on initial results.

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.

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).

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.