We called it the PA. Back in the day when I was involved in organising and setting up parties and small concerts. (each about once a year).
Not very accurate (looked it up just now) , but you might hear it referred to as such.
Yes, alsamixer (as does my main volume control app pavucontrol) does show volume as maxed out. It seems there's something after that that messes with the volume. :(
I'm here just to join you shouting out. Great peace of software.