A quick equal-airflow comparison of slipstream, new enermax
Posted: Thu Apr 10, 2008 7:42 pm
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.
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.