4 speakers , how to make each one play different sound?

I figured out a solution before by setting the AudioSetting with quad , and set the sound to 3D sound, but i could still hear some weak sound came from the other speakers , that’s not i want.
So i come here ask for help … how to make one speaker play a sound and the other speakers won’t hear anything?
I know this question is sooo petulant ,but please help =.=Thanks a lot

A bit late, but for any future visitors: this should solve that problem.