May push+pull improve performance/noise ratio on Noctua NH-U14S?

[steffeeh]

Reading the internet, you get the impression that people agree for most cases that push+pull doesn't have that much of a benefit in total cooling performance (i.e max fan speeds) unless you do a more specific type of cooling.

But let's not talk about cooling performance by itself with push+pull.
What I'm more curious about is if it's possible to keep the same amount of airflow while reducing the RPM and therefore part of the noise when adding a second fan to the heatsink.

I have a Noctua NH-U14S with the fan set to push and while it's a great cooler, I'm a bit of a silent computing freak and always strive for quieter results, hence why I've started to become curious about adding a second fan to the heatsik, just to make it a little bit quieter. 
At the moment the fan sit at around 600-700 RPM when I'm doing light tasks, so it's around these RPM's where talking about.

So how much would the noise go down if I were to add a second Noctua fan on the heatsink as pull and cut down the RPM to get somewhat equivalent airflow?

[it_dont_work]

Yes in general, push/pull at low rpm is quieter and gets better performance than running 1 fan at higher rpm. I've always done it and am pleased with the results.

 

That said, a pwm fan with a very wide rpm range (400-2500~) may be quieter at idle (since it's 1 fan) ands give you pretty good cooling performance when you ramp up its speed.

 

How much depends on the fans, I just changed the fans on my tt frio (the original version) with 2x corsair ml120s and the lower noise level is close to inaudible. But I could of used one since at idle the heatsink in my use case can run passive. Test some scenarios see what works, 

[SCHISCHKA]

Did you say push pull?

Push pull will not change the amount of air flowing through the heatsink so I do not think you will gain anything. If anything at lower rpm you will get less cooling.

I can get my Noctua fans down to 350rpm only on my CPU fan header; and the temperature is within operating spec. The system fan header only goes down as low as 500-600rpm. Maybe you can lower your fans by changing the header they are on and still stay within spec?

[steffeeh]

I can get my heatsink fan down to 200 RPM if I want to, though I've found a sweetspot for myself at 500-600 RPM when idle to keep it nice and cool without a ton of noise. But again, I'm always striving for improved silence, and are willing to try getting another CPU fan as pull of odds are good.

 

As for the video: HOLY SH!T

[Speakerator]

sure, it should help. With one single fan "forcing" air through the fins, due to the resistance of the fins and no matter the static pressure rating of the fan - there will always be some "backlash" / turbulence/ air not going through the fins, which creates noise against the fins. With a second fan aiding the first one, this effort is reduced. By itself, this means increased airflow or same airflow with lower RPM. How noticeable these improvements will be in the real world or whether the noise of the additional fan will outweigh the benefits - no idea. TBO, try it and in the worst case, you got yourself an additional high quality fan

[LogicalDrm]

I actually have U14S with push/pull config. The drop in temps isn't massive. Its about 5C with max temps. Idle and normal/gaming load are about same. There isn't noticable change in noise. But that might be more because of the way PWM controls of my board works. I'm using Speedfan and have set max speed for CPU fans to 80%. At low loads and idle 2nd fan isn't spinning. It kicks in when temps go over 55C or so.

 

Noctua, unlike some cheaper coolers, has even made their rubber mounts so that you have bit more free space between 2nd fan and heatsink.