Question Fractal Define 7 case fans & hub

[dexdice01]

Not sure if this is more relevant to cases or cooling. I'm quite fussy about quiet so my question below relates mostly to loudness of fan operation.

The Fractal Define 7 comes with three stock case fans. 2 x 140mm intake and 1 x 120 mm exhaust. They are DC fans but supposedly silence optimised, and they are designed to be connected to the case's fan hub which means they get voltage regulated based on CPU temps, in effect making them operate a bit like PWM fans (according to Fractal customer support). "The Nexus+ 2 Fan Hub is a PWM-hub, which when used right, makes 3-pin fans work as if they were a big, single 4-pin fan. "

I've been considering whether it's worth subverting the design and installing three PWM case fans instead, controlling them individually. My question is, do you think there would be any notable difference in dB levels if I did that compared to if I simply routed the stock fans (which are supposed to be aerodynamically engineered to be quiet) via Fractal's hub which would mean them presumably running somewhere around 300 rpm providing the CPU isn't hot.

 

[Euroman28]

Not sure if this is more relevant to cases or cooling. I'm quite fussy about quiet so my question below relates mostly to loudness of fan operation.

The Fractal Define 7 comes with three stock case fans. 2 x 140mm intake and 1 x 120 mm exhaust. They are DC fans but supposedly silence optimised, and they are designed to be connected to the case's fan hub which means they get voltage regulated based on CPU temps, in effect making them operate a bit like PWM fans (according to Fractal customer support). "The Nexus+ 2 Fan Hub is a PWM-hub, which when used right, makes 3-pin fans work as if they were a big, single 4-pin fan. "

I've been considering whether it's worth subverting the design and installing three PWM case fans instead, controlling them individually. My question is, do you think there would be any notable difference in dB levels if I did that compared to if I simply routed the stock fans (which are supposed to be aerodynamically engineered to be quiet) via Fractal's hub which would mean them presumably running somewhere around 300 rpm providing the CPU isn't hot.

I run the case with the following fan config.

3 top excaust 120 mm, 3 front intake fans and on stock 120 mm excaust fan in the back. That keeps my 12700k at the low 20s in idle and between 47c and 52c while gaming.

 

[Paperdoc]

With the focus on fan noise, a few points.

1. With NO change in which fans you use, ANY reduction is fan noise can be done only by reducing the fan SPEED, and that means for sure reducing COOLING. So making things quieter MAY sacrifice cooling and ultimately impact system lifetime. To break out of that the only way is to study fan specs and find replacements that generate less noise than the ones you have already at the same AIR FLOW delivery rates.

2. 3-pin and 4-pin makes no real difference here. Those design characteristics merely are parts of HOW a fan's speed is controlled. For any one fan design, the noise it generates at a specified speed and air flow is NOT affected by how that speed is set (DC or PWM Mode).

3. There is one thing you can try without changing the fans you have. As you say, those three 3-pin case ventilation fans are connected to a fan Hub supplied with the case. Based on the case's manual, that Hub controls the speeds of all the case fans, including a 4-pin fan of some type (OR AIO system) for cooling the CPU chip PLUS any case fans, be they 3-pin or 4-pin. In order to do that, the Hub has a connection to your mobo's CPU_FAN header and to no other header. That means that ALL fans' speeds are being controlled according to the temperature sensor inside the CPU chip. That is exactly the right thing to do for the CPU cooling system, but not optimal for CASE cooling. Every mobo has, in addition to the CPU_FAN header, some CHA_FAN or SYS_FAN headers dedicated to CASE ventilation fans. Almost all such headers CAN be configured in the BIOS Setup screens for those headers to use a different temp sensor on the motherboard as guidance, and that MAY direct your case fans to run more slowly (and quietly) that the CPU temperature sensor does. To make this work, though, you need to check the options available on your mobo's headers for one item: the header's MODE of control. Most offer you a choice of Voltage Control Mode (aka DC Mode) of PWM Mode. To control the speed of your 3-pin fans this MUST be set to Voltage Control Mode. Next, you have the small issue of connecting three such fans to mobo headers, and you may not have three such headers. So you need a simple Splitter like this

https://www.amazon.com/Cable-Matters-2-Pack-Way-Splitter/dp/B07PXLHNZ6/ref=sr_1_4?crid=9G3D00GTXUBA&keywords=fan+splitter&qid=1641748584&sprefix=fan+splitter,aps,105&sr=8-4

That's a 2-pack of 4-pin Splitters with three output arms each. You would need only one of these. If you're not familiar with Splitters, note these things:
(a) Sellers often mislabel Splitters and Hubs. A Splitter is simple. It merely connects all its fans to the host mobo header. It has only two types of "arms": one to connect to the host header, and two or more to plug in your fans. Do NOT get a HUB, which can look the same, but is distinguished by having a third "arm" type that must plug into a power output from the PSU. A HUB can be used only with 4-pin fans.
(b) Although these Splitters are 4-pin design, you CAN use them with your 3-pin fans - they simply won't use the fourth pin.
(c) ONE output arm of the Splitter has all four pins in it and is flagged with a label to use it "with fan speed signal". You must plug one fan into that one - it is the only arm that will send its fan's speed signal back to the host header. The speeds of fans on the other output arms will be ignored, but this has NO impact on fan speed control.
(d) In using a Splitter, you need to bear in mind that a single mobo fan header can supply up to 1.0 A max current for all fans connected to it. Your fans are spec'd for 0.20 A max current (140 mm) or 0.18 A (120 mm), so the total for those three is well below that limit - no problem.

So you get a Splitter as above, plug that into a mobo SYS_FAN or CHA_FAN header, then unplug all three of those case fans from the supplied Hub and plug them instead into the outputs of the Splitter. Go into BIOS Setup and make sure the header you are using is configured to use Voltage Control Mode (DC Mode), the default automatic speed control Profile, and (if you have a choice) the temperature sensor on the motherboard, not the one inside the CPU chip. Those fans as a group will be controlled to whatever is required to keep your mobo and its components cooled properly, and MAY run more slowly and quieter than if they were connected to the case-supplied Hub.

If that still gives you more noise than you want, you will need to search for replacement fans that offer significantly lower noise for the same air flow ratings.