I've made a new system, it has a 92mm exhaust fan at the upper rear. I have two fans here, one is 92mm, the other is 120mm. This will go on the lower front and will be the air intake.
Which would be best?
I've made a new system, it has a 92mm exhaust fan at the upper rear. I have two fans here, one is 92mm, the other is 120mm. This will go on the lower front and will be the air intake.
Which would be best?
As somewhat of a physicist, I'd say: use the larger fan as exhaust. This will get you the best flow in real situations, and also: the exhaust fan in a case is of more use than the intake fan since the exhaust fan is close to the CPU and GPU which generate the most heat. Thus use the best (=biggest, rpm and other variables considered equal) fan there.
Is it a large enough difference to be noticeable? Perhaps.
Can it rely on a lot more factors in this case (e.g. exact placement of cables/drives, dimensions of CPU/GPU cooling)? Yes. But my above recommendation should hold in more cases than not, and you'd need to analyze the airflow very closely to find the real-life flow. The indicators you have are the temperature sensors in the box: if you try it one way and they are higher than the other: switch.
Best is to measure mounting bracket.... probably quietest 12cm ventilator pumps as much air as the loudest 9cm one....
Depends on which size the case accepts (ie. has mounting holes for). If it can take both, then choose whichever better matches your requirements in terms of airflow and noise level. Usually larger fans can move more air with less noise than smaller ones, but without knowing exactly which fans you have, it's impossible to give a definitive recommendation.
If you have a way to control your fan speeds (eg SpeedFan, if you are using Windows), I would go with the larger one. A large fan at lower speed will move as much air as a smaller fan running faster. I assume you are looking at the same line of fans from a single manufacturer.
The noise curve does not necessarily increase linearly with rotation speed, so while the two fans may operate in the same dB range, I find that the larger ones can achieve the same effect while running a little quieter. Remember that even 1dB reduction in sound level is a significant improvement.
Also, since your case is not sealed, you generally don't have to pull as much air into the case as you push out. There will be an optimum balance of airflow where the load on your fans from both pulling and pushing air will yield the best airflow-to-noise ratio. Experiment.