And it seems like I have to adjust the sub volume for different CDs. Is this normal?
Unfortunately it can be.
Each sound recording may be mixed by different companies, different sound engineers. Some may pump up the bass, some may make the recording 'hot' (more treble).
This will be noticeable across music discs.
You have to find a level of your sub that is a good blend for the best and the worst, or simply don't play the worst as often as the best.
Keep in mind THERE ARE LIMITATIONS to this audio reproduction. You may not find a perfect solution regardless of what equipment you buy!!
