On the S9 controller there is two fan connectors but the board have place for 6 others fans connectors.
Do you know if these connectors placeholder receive power? If yes would it be possible to add fan connectors.
Here is an idea for a quieter miner. Remove the case and have 2 fans pointing directly at each blade sideways. So the fans would be pointing directly over the heatsink. With this setup I'm sure it would be possible to use lower cfm fans (quieter). 6 quiet fans is a lot better than 2 jet engines. Anyone tried this?
If the controller cannot power more than 2 fans it is possible to use a 1-to-3 splitter to power 3 fans per connector.
The case serves a cooling function too - directs airflow and probably dissipates heat as well. I would be very careful with a mod like that. Among other issues you'd likely have hot air getting mixed back into intake.