Connect a 9 volt battery to the speaker cable and watch the cones.
Do they all move?.
PS the speed at which you turn the master control has nothing to do with anything, it how far it ends up being turned that really matters.
Thank the good lord that the PA running your DI got its correct signal level without your help.
How come your amps master control wasn't pre set at the precise point taking into account your pre amps drive levels, at which the amp and cab sounds utterly great. Then all you have to do is EQ for the room.