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 Post subject: Want minimum speed of my PWM fan <799 RPM for free [SOLVED]
PostPosted: Sun Jun 23, 2013 3:12 am 
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The retail box of my Nexus D12SL-12PWM claims "500-2000 RPM" but I can't get it to spin slower than 799 RPM. It is attached to the CPU fan connector on a MSI Z77A-G45 motherboard. I see an old thread where SPCR users write that they were able to run this fan at much lower speeds and I gather that they did so with PWM enabled:
http://www.silentpcreview.com/forums/viewtopic.php?t=54984
How can this low speed be achieved with PWM enabled?

Here's what I have tried:

Using BIOS setup (during boot) I set the minimum PWM speed to 0% (minimum, of course) and the temperature target to 70C (maximum) but I cannot achieve CPU fan speeds below 799 RPM no matter what settings I use. I tried SpeedFan and it produced the same result, ~800 RPM when PWM speed was set to 0% (as well as with auto fan speed with flat-line 0% up to 56C (while the max CPU temp is 53C)).

Here's what I will try later this week, upon its arrival:
A second Nexus D12SL-12PWM ordered from a different retailer. I plan to mount it alone to test for sample variance, and then to mount both fans at the same time.

System specs:
Noctua NH-D14; both stock fans replaced with one center-mounted Nexus D12SL-12PWM @ 799-1333 RPM @ 21-53°C, in custom aluminum/elastomer foam fan box, blowing upward to a Kingwin Max. Power 650W PSU | MSI Z77A-G45 | i5-3570K | CORSAIR Vengeance 2 x 2GB 1600 | OCZ Agility 3 64GB | Seagate ST2000DM001 in aluminum drive carrier on elastomer foam pads, shutoff @ 17 minutes inactivity | LG 22X DVD Burner SATA GH22NS90B | Skyhawk case with facade, both brushed aluminum (by Eagle Tech) | LCD: ASUS VH236H | Win7 | Tiny Core Linux

The system is still not quiet enough; I can hear it right now, even with the room's window open to the birds chirping outdoors and with a parkway 300m away in the suburbs of NYC.


Last edited by nojunk on Fri Jun 28, 2013 10:08 am, edited 1 time in total.

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 Post subject: Re: Want minimum speed of my PWM fan <799 RPM... for free
PostPosted: Sun Jun 23, 2013 8:23 am 
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If you connect it up as a DC fan instead of PWM (ie. only 3 wires) and use a very low voltage then what is the minimum speed you can get? This might allow you to work around what you are finding.

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 Post subject: Re: Want minimum speed of my PWM fan <799 RPM... for free
PostPosted: Sun Jun 23, 2013 8:35 am 
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i vaguely remember MSI having some minimum duty cycle implemented in their BIOS. So, no matter what, some minimum fan speed determined by that threshold will not be undercut, regardless of BIOS settings.

So you might end up hooking the fans up to 7v or 9v + PWM.


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 Post subject: Re: Want minimum speed of my PWM fan <799 RPM... for free
PostPosted: Sun Jun 23, 2013 3:32 pm 
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Quote:
500-2000 RPM (+/- 10%)

so technically it might only get down to 700 rpm even with lowered DC voltage, or proper pwm.

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 Post subject: Re: Want minimum speed of my PWM fan <799 RPM... for free
PostPosted: Sun Jun 23, 2013 10:28 pm 
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Thank you all for the replies. I now have several more potential solutions to try.

edh wrote:
If you connect it up as a DC fan instead of PWM (ie. only 3 wires) and use a very low voltage then what is the minimum speed you can get?

I plan to try it and report back.

Pappnaas wrote:
i vaguely remember MSI having some minimum duty cycle implemented in their BIOS. So, no matter what, some minimum fan speed determined by that threshold will not be undercut, regardless of BIOS settings.

So you might end up hooking the fans up to 7v or 9v + PWM.

My data indicates that my MSI BIOS might have a minimum PWM speed of ~800 RPM on the CPU fan header. I wonder if the PWM system fan header has that limitation. I plan to try connecting my next Nexus PWM to the PWM system fan header as an experiment.

The second part makes sense, but I don't know whether to raise the voltage of the 12v negative lead or to lower the voltage of the 12v positive lead. The electrical engineer in me thinks that only one of these two options will result in a working PWM contol system.
I plan to try PWM fans in the following configurations: 5v 7v and two 6v. I may try 9v too if those are too slow; I have the Noctua heat sink's stock resistors handy (but I don't know where my Zener diodes are). If the MSI BIOS minimum speed is indeed 800 RPM then I expect to see the same RPM at many different voltages.

If all else fails I will look into BIOS mods... in 2 years when my warranty expires;-)

xan_user wrote:
500-2000 RPM (+/- 10%)

so technically it might only get down to 700 rpm even with lowered DC voltage, or proper pwm.

I can't justify buying a proper PWM controller at this time; the money could be better spent on other things.

I will, however, try a lower voltage as I mentioned earlier in this post. I'd gladly try almost anything. I'd be 14% happier with 700 RPM than I am now, with 800 RPM.

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 Post subject: Re: Want minimum speed of my PWM fan <799 RPM... for free
PostPosted: Mon Jun 24, 2013 7:22 am 
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have you actually determined the sound is from a particular fan? stop all but one fan temporarily with a ziptie, then repeat until offending noisemaker is found.

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 Post subject: Re: Want minimum speed of my PWM fan <799 RPM... for free
PostPosted: Mon Jun 24, 2013 11:36 am 
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xan_user wrote:
have you actually determined the sound is from a particular fan? stop all but one fan temporarily with a ziptie, then repeat until offending noisemaker is found.
I want to run the CPU fan at the minimum possible speed using the MSI motherboard's PWM fan controller (while still maintaining safe CPU temperatures).

I want to run the power supply fan using Kingwin's fan controller (while still maintaining safe PSU temperatures). This non-PWM controller is arguably comparable to the best PSU fan controllers reviewed on SPCR in airflow/sound*. I can hear using the stethoscope method that the PSU fan is quieter than the PWM fan.

Once I have done all I can to minimize the speed of both fans, I will measure the sound level of reach one (alone) by disconnecting the Noctua and running forced-convection CPU cooling only (because the PSU fan pulls air through the Noctua HS's fanbox) and then doing something similar with the power supply.

I recommend removing power from a fan to stop it, unless the person lacks the training to open up a power supply, or doing so would void its warranty. I'm safety-trained and not concerned about voiding my PSU's warranty.

PSA: Stopping a fan with a zip tie can theoretically reduce its performance, particularly its airflow:sound ratio, by both heating the coils and distorting the plastic fins, causing a permanent mechanical imbalance.

*I researched all of my system components (here and elsewhere) before buying. The MSI motherboard was not tested here because it is Battlefield oriented rather than silence oriented. I knew that going in. I'm trying to squeeze the best possible performance/sound out of the components I currently own.


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 Post subject: Re: Want minimum speed of my PWM fan <799 RPM... for free
PostPosted: Mon Jun 24, 2013 3:44 pm 
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that'll work too. but if there was one fan (or the PSU) that was defective, i'd personally want to know ASAP, so i could get a replacement sent out.

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 Post subject: Re: Want minimum speed of my PWM fan <799 RPM... for free
PostPosted: Tue Jun 25, 2013 12:56 am 
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Currently the both fans in the system (CPU @800 RPM & PSU @<800 RPM) show no symptoms of any defect and no audible ticking or e-noise.

If I detect any defect in any fan in the future, I will replace it with a spare I have on hand. Specifically another Nexus D12SL-12PWM (as I said in post #1) and the stock fans I removed from the Noctua NH-D14. As is typical for a SPCR user, I have a some additional fans on hand.

edit: I figured it out. I put a DT switch into the mid-heatsink fan's PWM line to rig it for silent running (with the option for flank speed upon my orders). I put a 10 ohm resistor in the 12v input line of the heatsink intake fan. The current idle numbers in SILENT MODE are:

Mid: 640
In: 530
Core: 38 max

I'm planning to mark this [solved] if possible.


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 Post subject: Re: Want minimum speed of my PWM fan <799 RPM... for free
PostPosted: Fri Jul 05, 2013 5:32 am 
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xan_user wrote:
have you actually determined the sound is from a particular fan?
Now that I have 2 CPU HS fans, both running below 600 RPM using grounded PWM wires (with the intake also fed 12v through a 10-ohm resistor), I have determined that only now is the (Kingwin Max. Power) PSU's fan the loudest of the 3 (again, using the stethoscope method).


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 Post subject: Re: Want minimum speed of my PWM fan <799 RPM for free [SOLV
PostPosted: Sat Jul 06, 2013 6:30 pm 
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glad you found it.
are you going to send it back for replacement, or go with something else?

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 Post subject: Re: Want minimum speed of my PWM fan <799 RPM for free [SOLV
PostPosted: Mon Jul 15, 2013 8:29 am 
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I'm going to live with the current noise level for the summer. This winter I'll swap the Kingwin PSU's stock fan out for the unused 120mm stock fan that came with my Noctua heatsink.

The spare Noctua 140 is too noisy to be used in my PC so I'm thinking about using it in the PC room's window, powered by an outdoor solar panel that is mounted above the window like an awning (for shade).

I never even considered sending a fan or PSU back for replacement - that's a great idea! I wish I could send back - at the vendor's expense - every fan and PSU that claims 15.5dB but in reality generates 15.6+dB!


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