Ideal Fan Configuration

[warriorunited]

Hello Everyone,

Just got another build for my GF, it's a Core Ultra 7 265k, ThermalRight Phantom Spirit 120 Evo, RTX 5070 Ti Asus Prime OC, and the most important here, the case Fractal Define North XL TG.

So, we bought a triple pack of Be Quiet Light Wings 140mm (not high speed), and our idea was to leave the three fans that already ship with the case (they are all intake), and add those three new be quiet fans for exhaust (one rear, two top), because she loves RGB and stuff.

Now the "problem", the fans that came with the case are... loud, she doesn't like it, even at 600rpm they are a little audible, and now we're starting to think in replace the default fans and put two lightwings for intake and one for exhaust.

What you guys suggest the most here? Leave the 3:3 combo, or replace fans and use 2:1 with only lightwings?

Thank you!

 

[Bill_Bright]

I am surprised she finds the fans that loud. My experience with FD fans is they are very quiet. But then my FD Design case has a front door with sound deadening materials. That case has, more or less, an open front. And my case sits down and off to the side.

Do you really need that many fans? Is 600RPM the slowest speed you can select? Check your motherboard userguide. Another option is the add a speed controller.

Your propose setup to add the 3 new as exhaust is right. But note you want a slight over or positive pressure in the case. That is, you want slightly more intake than exhaust. So maybe 2, 1 in back and 1 up top. This helps ensure the vast majority of cool air is drawn in through the filters. A good thing.

If under or negative, then a vacuum is created and then dirty air will be pulled in through any and all cracks and crevices and unused ports. Not good.

If me, I would consider just 2 fans in front and adding 2 exhaust fans. Then monitor your temps. I use and recommend Core Temp to monitor CPU temps in real time. Under Options > Settings > Notification Area, I have mine set to display "Highest temperature" only.

 

[warriorunited]

Because my PC is dead silent, I use silent wings 4 everywhere (dark rock pro 5, and 2 intake and 1 exhaust) and she likes that dead silence when the pc is idle, we have our computers on our right side over the desk, so it's impossible not to hear anything.

Thing is, she already back that triple fan pack of lightwings because she did really love that fans, they are very good looking fans and quality, and her idea was to use them all as exhaust like I said in the beginning, that's why suggested the alternative 2:1 using only the lightwings.

I can lower the fans speed a bit more in idle and then she won't hear a thing, but as soon the temps start to go a bit up she will complain and those lightwings are very good compared to Fractal Aspect ones that come with the case.

 

[_roman_]

Most case fans should be replaced so far.

Fans are in my point of view are underrated and very complicated.

It seems the english call it beating frequency.

NF-A14x25(r) G2 speed offset

Designed in Austria, Noctua's premium cooling components are renowned for their superb quietness, exceptional performance and thoroughgoing quality.

noctua.at

I think I suffered from that effect most likely. For some reason I run my setup without most fans, except the cpu tower cooler and the grpahic card for over 13 months. That experiment showed me where the noise makers are and has lead to a graphic card replacement.

I'm also thinking about future fan purchases and noise

the previous tech article from noctua leads to this product in my case.

NF-A14x25 G2 PWM Sx2-PP

The NF-A14x25 G2 PWM Sx2-PP is a set of two NF-A14x25 G2 PWM square-frame 140mm fans that are offset in speed, which can be beneficial in push-pull operation as well as in situations where two fans are operating side by side, such as in case cooling applications or on 280mm water cooling...

noctua.at

The NF-A14x25 G2 PWM Sx2-PP is a set of two NF-A14x25 G2 PWM square-frame 140mm fans that are offset in speed, which can be beneficial in push-pull operation as well as in situations where two fans are operating side by side, such as in case cooling applications or on 280mm water cooling radiators. When two fans are running at almost the same, constant speed in a push-pull configuration or, albeit to a lesser extent, side by side, their acoustic interaction can lead to undesirable harmonic phenomena such as intermittent vibrations or periodic humming due to interference, which can be heard as beat frequencies.

the alternatives in my case are far too expensive from bequiet to even consider them. For a small difference I could get the nocuta than.

I tend to buy stuff because I am curious or to learn something. In the worst case I wasted 80€ and learnt something. saving 20€ for two fans in total is not really worth buying bequiet.

dark rock pro 5

Well that cooler experience in my build some undesired frequencies sometimes. I run without sideglass panel and without the top metal cover. The computer stands in 105cm distance - nearest edge to the human ear. A slight finger push while the box is running shows the cpu cooler is the culprit, when the annoying frequency happens. Regardless if some screws needs to be tighten after a year... I need to rebuild the box anyway / change fans / change thermal paste ...

 

[Bill_Bright]

Because my PC is dead silent, I use silent wings 4 everywhere (dark rock pro 5, and 2 intake and 1 exhaust) and she likes that dead silence when the pc is idle, we have our computers on our right side over the desk, so it's impossible not to hear anything.

Make no mistake, I hate fan noise. This goes WAY WAY back to when I was into and repaired audiophile-class audio electronics - before I got into computers - and that happened in the mid 70s. If the sound is not intentionally in the original recording, it is objectionable and unacceptable. I mean Dolby was invented to suppress tape hiss!

You really cannot compare fairly your PC with hers PC UNLESS you have the same case, same fan configuration, same CPU, same CPU cooler, same graphics card, and same PSU. And even then, fan noise can be different due to how the motherboard/BIOS is monitoring temps and managing fans, and what Windows is doing at the time. This is because Windows does many "housekeeping" chores when its human is idle.

It should be noted that CPU and GPU fans tend to be much noisier than quality case fans. Make sure that is not what you or she are hearing.

I could not tolerate my PC sitting at ear level for that reason as I really hate fan noise. I would look at the physical layout and see if you can put the computer on (an inch or two off) the floor. One problem I see with the computer sitting on the desk is vibration noise being transferred to the desk, reverberating through the desk amplifying the noise, making it seem even louder.

Fans are in my point of view are underrated and very complicated.

Fan are indeed highly underrated, or at least misunderstood. And can be extremely complex and high tech.

Setting aside the pros and cons of the different type of motor bearings, it is important to understand a fan blade is essentially a propeller. And a propeller is essentially a spinning wing. Therefore they follow and are subject to the same Laws of Physics and aerodynamics as an aircraft's wing. My point being, a _roman_ noted, the design of a fan blade is very complex and complicated.

Unfortunately, air molecules have mass and so when the blade "chops" and "slices" through the air and "scoops" up and pushes the air through the fan, there is a tremendous amount of banging molecules hitting each other, hitting the blades, hitting the fan's housing as well as the case's vent.

Unfortunately too, there is no perfect solution that provides minimum noise and maximum air flow. So fan manufacturers must pick a balance and hope the consumer likes it. And of course, every consumer is different - not just in what they will tolerate, but in what they can actually hear. And whether the manufacturer takes it seriously or not depends on what sort of quality design and manufacturing they want to "invest" in.

BTW, you will hear all sorts of noise (pun intended) about bearing types. Some will claim fluid bearings are the way to go, others say ball and others talk about sleeve, I stopped paying attention to that long ago. Why? While fluid bearings, "in theory" and as a general category, tend to be the best and quietest, theory and real world don't always jibe - and it usually boils down to $$$ and marketing hype. A quality design, precision made, high-end sleeve bearing fan will be quieter and last longer than a poor design, cheaply made, fluid bearing fan - and probably cost less too. Bottom line: do your homework.

Beat frequency noise is real but I don't see where beat frequency would be an issue in this scenario. While front intake and rear exhaust might be considered a "push/pull" setup, the vibrating effects of a front fan does not affect a rear fan because of the distance between. Side by side fans can be affected, but much less so, and the effect is offset by other case fans. Plus, CPU and GPU fans counter the effects too. Not to mention, no two fans will spin at the exact same speed - and this scenario, there are 6, not counting the CPU, GPU and PSU fans.

The more likely scenario for beat frequency issues is with tower CPU coolers using 2 fans in push/pull.

That said, if vibrations are causing noise problems, the use of anti-vibration fan mounts can be of big help. You can also get sound isolation feet for the case. I would definitely consider this if the case sit on the desktop. But they are nice for the floor too as they elevate the case a little to allow more air underneath.

Another solution is some quality speakers or sound isolating headphones and cranked up Imagine Dragons!

 

[_roman_]

I'm sorry if I hijack the topic. I decided it's not worth to argue about 20-30€ extra so I ordered those double noctua fans. I do return stuff when it does not meet my expectations. MY car will cost me 3000€ this year to keep it in barely working condition. So I should not cheapskate if I want a "quiet computer".

Well I went for proper speakers and low noise build for some reason. The fans are next. Maybe I go back to the Noctua NH-D15 Gen1 cpu cooler. Than I have to replace the fans with the newer generation Aftermarket noctua generation 2 fans.

Beat frequency noise is real but I don't see where beat frequency would be an issue in this scenario.

You may read that noctua article again. I see the problem that all the fans are running with the same rpm and therefore generate all the same frequency noise pollution. The case also influence this. With only 4 PWM connectors on the cheapskate mainboards and cheap microcontrollers on the mainboard it's easier to move the problem fix to those noctua fans with different rpms. 2 years ago i had up to 9 fans in 120 or 140 mm in my case.

It's about the spectrum of the frequency band i can hear. Same stuff, regardless if it is a frequency for noise or a frequency in electronics. Same mathematics apply. (short summary for the main point of that beat frequency article of noctua, how i see it) Note: A starting point to read the basics
edit: this also applies for light to even more confuse some people - physics

 

[Shrek]

To keep the noise down at low speeds I went with 30mm thick fans

The Noctua fans come with a resistor option if one wants to keep the speed down.

 

[Bill_Bright]

You may read that noctua article again.

I did read and I understood the article. I might suggest you read it again and note the very first sentence. Note how the article is talking about CPU coolers with two fans and "sets" of two fans in push-pull configurations. Also take note of the images.

You might also read in the article about how we humans perceive the sound of beat frequencies. It is that of a modulated "tone" that increases and decreases in volume "like a beat". That is NOT the same as typical fan noise.

And then read what I said about it and in particular what I said about push-pull configurations with tall tower coolers and case fans in PC cases.

With the article and my comments in mind, I stand by what I said. Beat frequency exists. I did not say otherwise. I explained why in the OP's specific scenario, beat frequency is not the problem.

The main point again is the OP's full tower case is too cavernous for the push of the front case fans to interact with the pull of the rear (or top) case fans. And again, the sound cause by beat frequency interference is different from typical fan noise.