Hi
Rich beat me to it but heres my 2 cent worth
Since you mention firefox, I believe you will need to have pulseaudio set up in addition to alsa.
so if you bookmark
https://imgur.com/you can open a terminal and take a screenshot of you terminal command for alsamixer....which I find better than alsamixergui.....just my opinion.....so we can see if your mixer is unmuted for outputs and levels high enough
2) the command to run to take a screenie is
screenshot.sh
then upload it to ingur and copy and paste the link in your reply please.
3) now in the terminal run this command
speaker-test
and you will need the alsa-config package loaded to run that command
Can you report.....Do you hear sound?
4) Now lets look at Pulseaudio
We assume above is good....but continue even if you do not hear sound please
Please re-read the Apps info for pulseaudio.....Hint you need dbus running
later on.....we might suggest how you can automate that......but for now confirm dbus is running
/usr/local/etc/init.d/dbus status
dbus is running
if above shows its not running we start it with root powers like this
sudo /usr/local/etc/init.d/dbus start
5) now repeat
pulseaudio -vvv
do you see any errors
6) assuming none now load pauvcontrol and click the icon in wbar
go to the extreme right hand tab and set it up for your device
I have onboard sound speaker lead to desktop powered speaker or headphones so I need
analog stereo duplex.....while you may have a surround sound so need 5.1 etc
Let us know what you have please?
now play something and report