Comment 146 for bug 1332900

(In reply to Gary from comment #104)
> Created attachment 188581 [details]
> Sound Devices

with pulseaudio 7.0, you need to select surround2.1 profile which have two sliders volume and bass

 pulseaudio automatically change back to stereo when you plug the headphone

however when pulseaudio does not switch back to 2.1 profile after you unplugg the headphone

if your subwoofer use both rear left and rear left when speaker-test use -c4

you should also hear sound from subwoofer when speaker-test -c2 since snd-hda-intel copy front to all unused surround channel

that is the reason why you can hear signal from your two headphone jacks