The best and [easiest] way to lower voltage?

[Darkpoem]

Hi I am building an HTPC and I am think I will buy the Silverstone Grandia GD05B and the motherboard:
Asus P7H55-M/USB3.

If I then want to lower the voltage on the Chassi fans to 7 or 9V to lower the speed of the chassi fans, what is then the best way of doing it?

I would like to have a rather cheap an simple solution, everyone here on SPCR seems to tweak their fans in a lot of ways so it should be nice to hear a few comments on this issue.

Another question:
The fans that are connected to the PSU directly they cannot be controlled by some software or can they?

[Just an ordinary rabbit]

To undervolt fans connected directly to PSU to get either 5V or 7V:

• The 5V and 7V tricks: Do-it-yourselfers often tap into the voltage lines available from any PSU. Three conveniently available voltages can be obtained from the standard 4-pin Molex connector: 12V (yellow), 5V (red), and 7V (the difference voltage between 12V and 5V). The 7V line is not really that, and it is not recommended for more than one or two fans, especially if they draw much power. For technical reasons we won't cover here, it can cause damage to the PSU. For slow, low power fans, however, it is usually perfectly safe with a good quality PSU.

• Switches can be configured for multiple voltage feed to fans using the basic wiring information shown here. The DIY 12/5V switch is one example. There are many more variations that have been described in the SPCR Forum and all over the web. Your imagination is your main limitation.

• A simple way to get 6V is to wire two identical fans in series to 12V.

• Resistors in series (at least 1W rating) with the fan can also be used. 50~60 ohms usually provides around 5V from a 12V source. Adding ~25 ohms to 5V will give you around 4 volts. The numbers are approximate because the inductance/capacitance of the fan will affect the voltage drop.

• Zener diodes can also be used to reduce voltage — but still allowing the full 12V to pass on startup.

http://www.silentpcreview.com/article63-page1.html

If the motherboard supports it, you could set the BIOS to control the fans instead which would probably be easier and more accurate.

The fans that are connected to the PSU directly they cannot be controlled by some software or can they?

Not without using some sort of fan controller, no.

[Darkpoem]

thx! Then I just have to make sure I buy a silent 120mm fan that can be undervoltaged

[Das_Saunamies]

Unless you've already tested the setup somewhere and found out the exact RPM you want, adjustable fans would be a better move. 7V is such a standard just because it's easy to procure with DIY, it's not the be-all, end-all solution.

If that Asus mobo has the same control scheme mine does (see the sig), I would recommend some PWM fans and an Akasa splitter cable. Result is inexpensive, automatic, adjustable fan control.

[Darkpoem]

I have understood that the Silverstone Grandia comes with 3 rather silent fans according to SPCR reviews of the chassi. I don't think I will change them if I don't have to.

I thought of buying a fan controller such as Scythe Kaze Master 5.25" but since the chassi only supports one external 5.25 it is not an option since I would like a blueray drive.

[quest_for_silence]

I thought of buying a fan controller such as Scythe Kaze Master 5.25" but since the chassi only supports one external 5.25 it is not an option since I would like a blueray drive.

Use a piece of software to control your fans.

[Darkpoem]

But I can't control the fans connected to my power supply can I?

[quest_for_silence]

But I can't control the fans connected to my power supply can I?

Just in some not common and often rather inefficient way, afaik.

The most often used one is to detach the PSU fan cable from its socket, take it outside the PSU, maybe using an extension, and then connecting it to a motherboard header, or to a fan controller one.
This way void the PSU warranty and does not guarantee that the fan may still cool the PSU in the most effective and safest way.
Just as examples, I do so with a NSK3480, while our host, MikeC, do the same with a NSK1480.

Otherwise, instead to drive the original PSU fan with a different controller, you can either try a PSU fan swap (can't directly control its behaviour, void the warranty, expose to some reliability issue), or swap the PSU itself with a quieter one.

[Just an ordinary rabbit]

But I can't control the fans connected to my power supply can I?

Just in some not common and often rather inefficient way, afaik.

The most often used one is to detach the PSU fan cable from its socket, take it outside the PSU, maybe using an extension, and then connecting it to a motherboard header, or to a fan controller one.
This way void the PSU warranty and does not guarantee that the fan may still cool the PSU in the most effective and safest way.
Just as examples, I do so with a NSK3480, while our host, MikeC, do the same with a NSK1480.

Otherwise, instead to drive the original PSU fan with a different controller, you can either try a PSU fan swap (can't directly control its behaviour, void the warranty, expose to some reliability issue), or swap the PSU itself with a quieter one.

I think the OP was referring to fans connected directly to the PSU (ie, not powered by a mobo/fan controller), not the fan inside the PSU itself.

The 5v and 7v mods I mentioned earlier are cheap and easy to do, but if they don't offer enough control then you can solder a resistor into the fan's power cable or perhaps use a fan controller that mounts in the PCI slots like this one..

If your fans don't have the standard 3 pin fan connector, you might manage to find an adapter to let you plug it into your mobo and use it's fan controller. Alternatively, you could buy some PWM fans and control them with the mobo.

[quest_for_silence]

I think the OP was referring to fans connected directly to the PSU (ie, not powered by a mobo/fan controller), not the fan inside the PSU itself.

Well, eventually I see now: he does not own those parts, he's just talking about them, this is why he's wondering about undervolting fans, and why he just can't try to use any software to control them. Ok, sorry.

Being so, to me the right way is to choose a better motherboard (i.e. one with more than one 3-pin controllable fan header), and then use a software to control them: secondly, to replace the cable fans with some common 7V tails (if he's able to do so, he may sold a 20-30R 5w resistor - 1w ones blow away too easily, today - on each fan, as you already suggested, or even buy something like Sharkoon, Revoltec or similar cables for a few bucks, if in case: IMO more probably that note he won't use them at all, as temps are higher but not untolerable without them), if he likes the most that Silverstone.

[Darkpoem]

Thx for all your input, as I have understood it the fans are really quite at 7V and it seems that the easiest way to get a silent htpc is to just use 7V as the SPCR review about the Siverstone chassi mentioned and then its probably the best way to to as "Just an ordinary rabbit" said about using 12 and 7V pins and do a littel contact for the 2 or three chassi fans. I am not worried about the PSU fan since I am going to but the Nexus Value 430W which is very quite as I have understood it.

Thx to you all for your comments!