Quoted from Av8:
I never use the Volume contoller. Just leave it in the box. It only reduces input to cab speaker. Which is not needed IMO. More bass the better.
This shows a misunderstanding of how the volume control works.
If you think "more bass the better", then you *need* the volume control.
While you are correct that it only reduces input to the cabinet (main) speakers, it does not reduce the volume to the subwoofer. Turning down the volume controller allows you to turn UP the volume on the machine, which in turn increases the bass to the subwoofer (without making the overall sound level too high). In other words it allows you to be able to better blend the bass with the treble.