Xbox 360 Slim 4GB - Noctua NF-A9 (PWM)
This mod was pretty much a waste of time. I mounted the fan to the heatsink. However you should NOT do that. I ended up with a higher db and heat when doing so. Only mount / aligne the fan to the case:
Mount fan to the heatsink (Trinity) (Valhalla)
44 db (Front of the console)
60 db (Fan exhaust)
31 db (1 Meter from console)
Mount fan to the case plastic / rf sheild (Trinity) (Valhalla)
39 db (Front of the console)
55 db (Fan exhaust)
31 db (1 Meter from console)
Stock fan (Corona)
32 db (Front of the console)
42 db (Fan exhaust)
30 db (1 Meter from console)
So even with the Noctua NF-A9 (PWM) fan it doesnt improve anything. Save money and time by NOT doing this mod.
EDIT: This was done with decibel noise levels in mind only. Not to make it cooler. If you are out to cool it more and don't mind the higher decibel noise levels i would say it is worth it. Here is a follow up to this video: https://youtu.be/UHTnGnIAavk