Xbox 360: 120mm fan mod for quietness

I wanted to watch a movie yesterday, but my Xbox's fans are too loud. So I decided to do something about it!

The problem

Upon opening the case and removing the DVD drive, we see this lovely duct directing airflow in the case (note that the fans are pointed outwards, so the ducts are sucking air from the heatsinks).

Underneath, these two 70mm fans are surely to blame for the excessive fan noise.

So I went went to bed pretty late last night (~3am) with a plan of attack: replace these small screaming fans with a larger, more reasonable fan that can move the same amount of air without making such a fuss about it.

The solution

Then I woke this morning at 8am, clearly excited about this project because I simply could not fall back asleep. Anyways.

I don't want to mess with the air flow pattern because someone clearly put a lot of thought into designing it. So I'm keeping the old duct and fan housing, but removing the now-obsolete fans:

The new 120mm fan poses one slight problem: it's way too big. I will have to mount it outside with some external ducting to pull air out through the original opening.

Here I've routed the fan power outside (yeah we're probably gonna fail EMC testing) and cut away some of the plastic shell so that the duct can mount directly to the chassis:

I used foamcore to build the external ducting. Given how heavily my undergraduate education utilized this prototyping material, I spent an embarrassingly long time trying to figure out how to build the shape that I wanted. 

Part of the problem was that my initial plan was not actually feasible in a Euclidean space, so that posed some implementation challenges. After several iterations, I finally figured out the how to connect the dots using some advanced foamcore origami:

And attached everything together in a giant mess of hot glue!

The Xbox normally sits in this orientation on a shelf in the TV stand. The shelf is 6" tall and this contraption fits with about 1" of clearance. The shelf has a back, but the top 3.5" of it is open, so the fan is angled upwards to direct the hot air towards this opening. 

Testing

I measured the Xbox's noise level using an app on my phone (Decibal 10th by SkyPaw Co. Ltd). Measurements were taken from 18" away, and the baseline noise level was about 40 dB for each test (this seems a bit high; perhaps some calibration is in order).

Old (2x 70mm fans): 60 dB

New (120mm fan): 50 dB

And we see from these spectrograms (taken while the system is powering up) that the modified system is missing the higher-frequency whine associated with the old fans. The 120mm fan is practically silent.

Original system

With 120mm fan mod

But you may notice there is still a line remaining at about 1.3 kHz. It turns out there's a tiny fan inside the power brick! I had never noticed before because its noise was dwarfed by the fans on the Xbox itself, but now it's the loudest thing in the system.

Maybe some other day. Now for some movies and video games! I mean *ahem* stress testing.