Question Question about the Noctua NH-L9x65. Help?

Jan 7, 2021
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My case is too small for a normal tower CPU cooler so I got this one, but I'm a little confused on the direction the fan is suppose to face. Is it suppose to blow air onto the heatsink or away from it? I asked around but someone told me that its suppose to blow air away from the heatsink (exhaust the hot air from the heat sink) but many videos on YouTube show the person installing it with the fan blowing air onto the heatsink.

I have 2 fans in the front as intake, 1 fan in the back and 1 in the top as exhaust.

CPU is Intel Core i5

Cooler is the Noctua NH-L9x65

Case is the Antec P50
 

Phaaze88

Polypheme
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You actually have a couple options here.
Just experiment with the fan facing up and facing down, and see what happens with both cpu and gpu thermals.
One will be better than the other, but it can vary between setups.
 
Jan 9, 2021
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You actually have a couple options here.
Just experiment with the fan facing up and facing down, and see what happens with both cpu and gpu thermals.
One will be better than the other, but it can vary between setups.
Just to expand on this a little: it depends on your airflow, and the cooler fan's access to fresh air.

Looking at the Antec P50, it looks like the air coming in from the front might be getting mixed up with warm air within the case (traveling over any components installed between the front fans and the motherboard, or exhausted upward from the GPU), then pulled over the CPU cooler before getting exhausted out the back. If so, then pointing the cooler down is just pulling warm air directly onto your components, which won't help your performance or cooling. In that case, you might want the fan pointing up. You're still pulling warm(ish) air through the heatsink, but you aren't then pushing it over the motherboard. However, if those front fans have higher static pressure, such that they're blasting that air right at the motherboard you might point the cooler fan down to help pull that air over your components (and the heatsink).

Question, though: that case says its rated for up to 130mm for a CPU cooler, so why not consider getting a NH-U9S? That cooler is amazing, vastly outperforms the L9x65, and is only 125mm. It's generally considered one of (if not the) best 92mm fan tower coolers, and it's currently on sale @ Newegg: https://www.newegg.com/noctua-nh-u9s/p/N82E16835608067?Description=nh-u9s&cm_re=nh-u9s-_-35-608-067-_-Product&quicklink=true
 
Jan 7, 2021
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Just to expand on this a little: it depends on your airflow, and the cooler fan's access to fresh air.

Looking at the Antec P50, it looks like the air coming in from the front might be getting mixed up with warm air within the case (traveling over any components installed between the front fans and the motherboard, or exhausted upward from the GPU), then pulled over the CPU cooler before getting exhausted out the back. If so, then pointing the cooler down is just pulling warm air directly onto your components, which won't help your performance or cooling. In that case, you might want the fan pointing up. You're still pulling warm(ish) air through the heatsink, but you aren't then pushing it over the motherboard. However, if those front fans have higher static pressure, such that they're blasting that air right at the motherboard you might point the cooler fan down to help pull that air over your components (and the heatsink).

Question, though: that case says its rated for up to 130mm for a CPU cooler, so why not consider getting a NH-U9S? That cooler is amazing, vastly outperforms the L9x65, and is only 125mm. It's generally considered one of (if not the) best 92mm fan tower coolers, and it's currently on sale @ Newegg: https://www.newegg.com/noctua-nh-u9s/p/N82E16835608067?Description=nh-u9s&cm_re=nh-u9s-_-35-608-067-_-Product&quicklink=true

Thank you for your reply, it was very informative. I couldn't use a CPU cooler that stretches out like that. The case itself is fairly narrow. I had to buy a low-profile one so I could close the case.

The Antec P50 has 2 chambers, its kind of weird but I have:

One 120mm fan in the front.
One 90mm fan in the front (on the other side/chamber)
Both the 120mm and 90mm fans came with the case. I don't know if they're SP or AF

In the back in I have a 90mm exhaust fan and ontop I have another 120mm exhaust fan.

Is my setup still okay with those? having the CPU fan blow air onto the heatsink?




Separate question: I heard the Noctua NH-D15 was the best. Is the NH-U9S better?
 
Jan 9, 2021
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Thank you for your reply, it was very informative. I couldn't use a CPU cooler that stretches out like that. The case itself is fairly narrow. I had to buy a low-profile one so I could close the case.
Well, the manufacturer spec says it's rated for up to 130mm in cooler height, so in theory anything shorter than that would fit. I might suggest you honestly take a ruler and see if there's 130mm of space between the motherboard and the case wall. The reason I suggest that is you're leaving cooling capacity on the table if you use an L9x65 in a case that could take a larger cooler.

Don't get me wrong - that L9x65 is a solid low-profile cooler, and it's rated to handle up to ~80W of CPU. You said you have an Intel "i5", but depending on the model that could be a TDP of 65w, or possibly 95W. So if you're running at stock speeds with good case cooling and ventilation that cooler should be sufficient. However, if your CPU has a TDP of 95W - OR you plan to overclock in any way - you might find yourself getting thermally throttled.

One 120mm fan in the front.
One 90mm fan in the front (on the other side/chamber)
Both the 120mm and 90mm fans came with the case. I don't know if they're SP or AF

In the back in I have a 90mm exhaust fan and ontop I have another 120mm exhaust fan.

Is my setup still okay with those? having the CPU fan blow air onto the heatsink?
Honestly, that all sounds fine. You've basically got neutral pressure, and you're exhausting air from the top of the case so there's probably not a lot of loitering heat. However, because your graphics card sits on the bottom of the case it might be exhausting air into your case (depends on the make and model), which is getting pulled across your motherboard as it's exhausted out the back and top. That might mean warmer air is getting pulled over the motherboard from bottom to top.

End of day, here are my three suggestions for you:
  1. If you can put a larger cooler in that case, consider it. The NH-U9S is a pretty top-flight low profile tower cooler that clears 125mm, and should fit in your case. There's another Noctua (NH-D9L) that is only 110mm tall that's even more likely to fit in your case that would also be better than the one you have (although the U9S is better than the D9L). I like Noctua fans, but if you google CPU coolers and the max clearance for your case you will probably find a lot of recommendations at different price ranges.
  2. If you're keeping the L9x65, just try it in its stock configuration. There's a reason they set them up that way - it's generally the more efficient way to run that cooler.
  3. If you use it in its stock config, and you find that your CPU is getting too hot to perform effectively, then try flipping the fan itself the other direction.
Separate question: I heard the Noctua NH-D15 was the best. Is the NH-U9S better?
The D15 is unarguably one of the best air coolers on the market, and it is significantly better than the NH-U9S. It's also larger, and would definitely not fit in your case.

Here's a big list of performance ratings for CPU coolers: https://www.tweaktown.com/reviews/7292/noctua-nh-l9x65-low-profile-cpu-cooler-review/index.html#Test-System-Setup-Thermal-Tests-and-Noise-Results

You can see where the L9x65 landed on this list. It performed poorly, but don't let that worry you - it was being tested on a CPU that was a higher TDP than it's supposed to support.
 
Jan 7, 2021
3
0
10
0
Well, the manufacturer spec says it's rated for up to 130mm in cooler height, so in theory anything shorter than that would fit. I might suggest you honestly take a ruler and see if there's 130mm of space between the motherboard and the case wall. The reason I suggest that is you're leaving cooling capacity on the table if you use an L9x65 in a case that could take a larger cooler.

Don't get me wrong - that L9x65 is a solid low-profile cooler, and it's rated to handle up to ~80W of CPU. You said you have an Intel "i5", but depending on the model that could be a TDP of 65w, or possibly 95W. So if you're running at stock speeds with good case cooling and ventilation that cooler should be sufficient. However, if your CPU has a TDP of 95W - OR you plan to overclock in any way - you might find yourself getting thermally throttled.


Honestly, that all sounds fine. You've basically got neutral pressure, and you're exhausting air from the top of the case so there's probably not a lot of loitering heat. However, because your graphics card sits on the bottom of the case it might be exhausting air into your case (depends on the make and model), which is getting pulled across your motherboard as it's exhausted out the back and top. That might mean warmer air is getting pulled over the motherboard from bottom to top.

End of day, here are my three suggestions for you:
  1. If you can put a larger cooler in that case, consider it. The NH-U9S is a pretty top-flight low profile tower cooler that clears 125mm, and should fit in your case. There's another Noctua (NH-D9L) that is only 110mm tall that's even more likely to fit in your case that would also be better than the one you have (although the U9S is better than the D9L). I like Noctua fans, but if you google CPU coolers and the max clearance for your case you will probably find a lot of recommendations at different price ranges.
  2. If you're keeping the L9x65, just try it in its stock configuration. There's a reason they set them up that way - it's generally the more efficient way to run that cooler.
  3. If you use it in its stock config, and you find that your CPU is getting too hot to perform effectively, then try flipping the fan itself the other direction.
The D15 is unarguably one of the best air coolers on the market, and it is significantly better than the NH-U9S. It's also larger, and would definitely not fit in your case.

Here's a big list of performance ratings for CPU coolers: https://www.tweaktown.com/reviews/7292/noctua-nh-l9x65-low-profile-cpu-cooler-review/index.html#Test-System-Setup-Thermal-Tests-and-Noise-Results

You can see where the L9x65 landed on this list. It performed poorly, but don't let that worry you - it was being tested on a CPU that was a higher TDP than it's supposed to support.

Thanks again for the advice! Do you mind if I ask you one more question about my main build?

This is a setup of what it's airflow looks like: View: https://imgur.com/a/69Dp5vx


How is the airflow for the case? I tried to make it as optimized as I could. Is it any good?

The case is a corsair 750D airflow edition.
 

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