Found: the world's quietest production 120mm fan
Posted: Sat Jun 30, 2007 10:46 am
This is not a joke.
We're talking about standard 7-blade 120mm x 25mm fans, normal pitch, widely available for purchase. That means you can see for yourself.
I was looking among the usual suspects - Yate Loon, GW NCB, S-Flex, fans like that. I was looking for fans with low bearing noise, whose bearing noise scaled down as the RPM dropped. This latter point requires holding the fan closer and closer to your ear to confirm there's no discontinuity in bearing noise.
Among the fans that met the above criteria, the champion would be the one that turned the lowest RPM, yet kept on running.
Obvious fans to test include 800RPM fans such as the Evercool EGF and the S-Flex D. The latter won't run at 5V (I'm talking running, not starting), and the EGF runs at 6V but not 4V and I didn't try to pin it down closer than that.
The GW NCB was a prime candidate. I used my newish Extech stroboscope for measuring RPM and a 4-1/2 digit dmm to measure the voltage. Why voltage? To keep the stroboscope numbers honest. A fan turning 1000RPM will also "strobe" at 500RPM and 333.3RPM and 250RPM... you get the idea.
I selected one of my NCBs at random, and here's what I got: 12V 1289, 8V 971, 6V 746, 4V 491, 3.5V 405, 3V 319, and 2.8V 141RPM. If you plot that, you'll see that the fan motor controller IC goes to hell below 3V, but is still hanging by its fingernails - barely - at 2.8V. I think I'd be comfortable running the NCB at 3V, which is 319RPM.
All the quiet 120mm fans that can run at 1000RPM measure about the same dBA at that RPM. A fan running 319RPM is 29.77dBA quieter than at 1000RPM by the 60*LOG10(rpm1/rpm2) rule. So does that make the NCB our quiet-fan champion? Heck no! I found a fan that's lots quieter!
Our champion measured 12V 1082, 8V 715, 6V 510, 4V 250, 3.5V 176, and 3V 100.5RPM. I report the .5 because if I put down 100 you'd think I was making it up. 100.5 is the RPM I measured at 3V.
Again, a plot shows that this fan's motor controller IC goes to hell below 3.5V. But the 176RPM at 3.5V looks solid; I'd even be comfortable with a slightly lower voltage and 150RPM since the fan still runs at 100RPM.
A fan running 150RPM is 49.43dBA quieter than at 1000RPM by the 60*LOG10(rpm1/rpm2) rule. That, folks, is our champeen. And I have good reason to believe no other fan can come close to that figure. Why? Because in Devonavar's latest 120mm fan review, our champeen had by far the lowest power consumption at any given RPM. No other fan came remotely close.
[Since the fan did run at 100.5RPM, that's 59.87dBA lower than at 1000RPM, but I wouldn't trust the fan to run at that speed month after month.]
Ladeez and gennulmen, our low-noise champeen in the 120mm weight class: the Enermax Marathon fan with Enlobal bearings! I call it the magfan.
We're talking about standard 7-blade 120mm x 25mm fans, normal pitch, widely available for purchase. That means you can see for yourself.
I was looking among the usual suspects - Yate Loon, GW NCB, S-Flex, fans like that. I was looking for fans with low bearing noise, whose bearing noise scaled down as the RPM dropped. This latter point requires holding the fan closer and closer to your ear to confirm there's no discontinuity in bearing noise.
Among the fans that met the above criteria, the champion would be the one that turned the lowest RPM, yet kept on running.
Obvious fans to test include 800RPM fans such as the Evercool EGF and the S-Flex D. The latter won't run at 5V (I'm talking running, not starting), and the EGF runs at 6V but not 4V and I didn't try to pin it down closer than that.
The GW NCB was a prime candidate. I used my newish Extech stroboscope for measuring RPM and a 4-1/2 digit dmm to measure the voltage. Why voltage? To keep the stroboscope numbers honest. A fan turning 1000RPM will also "strobe" at 500RPM and 333.3RPM and 250RPM... you get the idea.
I selected one of my NCBs at random, and here's what I got: 12V 1289, 8V 971, 6V 746, 4V 491, 3.5V 405, 3V 319, and 2.8V 141RPM. If you plot that, you'll see that the fan motor controller IC goes to hell below 3V, but is still hanging by its fingernails - barely - at 2.8V. I think I'd be comfortable running the NCB at 3V, which is 319RPM.
All the quiet 120mm fans that can run at 1000RPM measure about the same dBA at that RPM. A fan running 319RPM is 29.77dBA quieter than at 1000RPM by the 60*LOG10(rpm1/rpm2) rule. So does that make the NCB our quiet-fan champion? Heck no! I found a fan that's lots quieter!
Our champion measured 12V 1082, 8V 715, 6V 510, 4V 250, 3.5V 176, and 3V 100.5RPM. I report the .5 because if I put down 100 you'd think I was making it up. 100.5 is the RPM I measured at 3V.
Again, a plot shows that this fan's motor controller IC goes to hell below 3.5V. But the 176RPM at 3.5V looks solid; I'd even be comfortable with a slightly lower voltage and 150RPM since the fan still runs at 100RPM.
A fan running 150RPM is 49.43dBA quieter than at 1000RPM by the 60*LOG10(rpm1/rpm2) rule. That, folks, is our champeen. And I have good reason to believe no other fan can come close to that figure. Why? Because in Devonavar's latest 120mm fan review, our champeen had by far the lowest power consumption at any given RPM. No other fan came remotely close.
[Since the fan did run at 100.5RPM, that's 59.87dBA lower than at 1000RPM, but I wouldn't trust the fan to run at that speed month after month.]
Ladeez and gennulmen, our low-noise champeen in the 120mm weight class: the Enermax Marathon fan with Enlobal bearings! I call it the magfan.