Spatialised sound w/ Megalodon Maelstrom headset

I'm using a Megalodon Maelstrom Headset (old-ish Razer 7.1 USB). When in 7.1 mode, all the sound spatialisation is "blurry". It's sometimes even difficult to know if sounds come from the right or the left, let alone front or back.
In stereo mode, it works as expected.

Maybe relevant, maybe not, it worked fine regarding spatialisation with the original Insurgency.

It still works fine with other games. So I'm fairly confident it's still about some kind of library that hasn't been added or something.

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