Re: Option to force 7.1 sound
Right-click the speaker icon on your taskbar, click 'Sounds' then 'Playback'. Right-click on your device and make sure it's set to the default device. If you have the option "Configure Speakers" click that and see if there are other options such as 5.1 and 7.1.
In the Apex in game settings audio tab it should say at the bottom what the windows configuration is. On mine it says 5.1.