Side affects of adjusting DC fan speed?

[Xdrone]

If I were to change a fan speed curve of a fan that isn't pwm, but uses DC power, through the BIOS... Are there any noticeable side affects when compared to PWM? Such as heat being released from low efficiency?

[W-L]

5 minutes ago, Xdrone said:

If I were to change a fan speed curve of a fan that isn't pwm, but uses DC power, through the BIOS... Are there any noticeable side affects when compared to PWM? Such as heat being released from low efficiency?

If the fan is 3 pin it can only be controlled via DC voltage control, PWM can allow for lower rpms depending on the fan providing a larger controllable range on the low side and in terms of starting the fan. 

[Xdrone]

1 minute ago, W-L said:

If the fan is 3 pin it can only be controlled via DC voltage control, PWM can allow for lower rpms depending on the fan providing a larger controllable range on the low side and in terms of starting the fan. 

How do I know what range I will be getting with DC?

The fans are SP120 rgb.

[W-L]

Just now, Xdrone said:

How do I know what range I will be getting with DC?

The fans are SP120 rgb.

You have to test them to see what you get, some fans have a lower starting voltage some higher so it varies. 

[Spuriae]

Maglev bearing fans may not work properly at low voltages. Otherwise you'll usually get a slightly lower minimum RPM on PWM, but performance across the board will be essentially the same.

4 minutes ago, Xdrone said:

How do I know what range I will be getting with DC?

The fans are SP120 rgb.

From Thermalbench, 3.25V starting.

[Xdrone]

15 minutes ago, Nimrodor said:

 

Where did you find this image

[Spuriae]

46 minutes ago, Xdrone said:

Where did you find this image

http://thermalbench.com/2016/09/02/corsair-sp120-rgb-led-120-mm-fan/3/

[LogicalDrm]

Like said, 3pins have lower control range and there might be some revving. Usually 3pins go down to 30% of max rpm. Thats about the speed they need to startup while most PWMs can start at 10-15%. With good quality 3pins, the difference in what you actually hear or see in performance is less noticeable.

[thedons1983]

20 hours ago, Xdrone said:

How do I know what range I will be getting with DC?

The fans are SP120 rgb.

I've got a couple of DC SP120s (non RGB), that I can test under DC control on my MB to confirm range, if you like?  They are the quiet edition fans though, so bear that in mind.  FYI and IMO, they sound awful no matter what the RPMs and are being returned.

[Xdrone]

7 hours ago, thedons1983 said:

I've got a couple of DC SP120s (non RGB), that I can test under DC control on my MB to confirm range, if you like?  They are the quiet edition fans though, so bear that in mind.  FYI and IMO, they sound awful no matter what the RPMs and are being returned.

Oh yeah that would be amazing if you could do that ?

[thedons1983]

6 hours ago, Xdrone said:

Oh yeah that would be amazing if you could do that ?

No worries, I'll do it over the next day or so and report back!

[thedons1983]

On 8/13/2017 at 4:08 AM, Xdrone said:

Oh yeah that would be amazing if you could do that ?

Here's the screenshot of the Asus fan Xpert RPM range assessment for the Corsair SP120 Quiet Edition (3-pin), running from a 4 pin true PWM chassis fan header, but in DC mode.  Hope it helps!