Hight CFM/RPM fan vs MX6 controller

[G78]

Ok tried 4 kind of fans on GPO#1 on my MX6 today.
Now i would like to know how to fix a problem on it. Maybe its a configuration i need to do, or add a componant between the fan and the controller i dunno, but to elaborate the problem i am showing my lil test result below.

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60mm Thermaltake Volcano 7 40 CFM 4890RPM
This one went throught the test like a charm. We can barelly hear any speed variation. Unless your ear is against the fan frame itself. Also this fan is easely below 40 Db on the noise scale.

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92mm Tornado from Vantec 119 CFM 5300RPM
This one seems to be ok until it lowers from its full speed.

Then every 1,5 seconds(maybe a bit less) the fan seem to take a fast RPM peak for like 0,25 seconds then goes back to its previous speed. A bit like if it was a saw signal. The average speed of the fan does vary from the setting putted in LCDC on both percentage and Digital bus mode. but the problem is still there on both cases.

This fan makes about 56,4 Db of noise at full speed, so using a fan controller when the cpu is idle is a most. I even got a dampening noise kit to go with this one.

The sudden speed peak gets very annoying afther awhile, a bit like constantly blowing a whissle in the ears every seconds.

Everything else went perfectly.

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80mm Tornado from Vantec 84,1 CFM 5000RPM
This one as the same problem as its big 92mm bro but the hight pitch noice is even higher. 55,2 DB on the noise scale.

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120mm Panaflo From panasonic 114,7CFM 2750 RPM
This one is the most quiet fan i ever had for its size, and it has a really hight CFM for its class, the best on the market as far as i know.

We hear again the speed variation, like on the 2 previous one, exept this time it aint annoying at all since the noise at full speed aint a problem with its 45,5 Db

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So basically am guessing the Hight power GPO controller on my MX6 handle better 80 mm or lower size fan with low RPM and average CFM. Now as for WHY it does that sudden RPM burst every 1,5 seconds... That i would like to know myself and also know how to fix the problem.

In hope to be enlighten soon on this

[Tom]

G78,

What we noticed with the bigger fans is there has been more problems with the noise. What you can try is to adjust the frequency of the pwm with the program bootedit. You can also try placing a large capacitor value across power and ground to eliminate any high frequency noise. As for the sudden RPM burst every 1,5 seconds, that is a side affect of rpm sensing. If you shut off rpm sensing, the burst will go away. So far we are actively designing an improved way of rpm sensing in our future products.

If you have anymore questions or concerns, please feel free to post them.

Best Regards,

[b08maz]

The best thing I have found is adding this to each large fan. It is better than mCubed version. There is minimal voltage loss and my clicking and purring large fans quieted down some with this. You can buy all the parts at Radio Shack, 2 10 ohm resistors, 1 1000microfarad electrolytic cap and a female and male fan connector which you can salvage from a Y-connector like I did. I measured the square wave with scope and the best frequency seems to be 400-610hz. The fan will have 10.4 volts going to it. With the fan out of the picture it's an open circuit.