OK, I'm a new owner but pretty sensitive to audio. one of the disappointments in our 2012 Model S is that the premium audio did not live up to my expectations and did not sound as good as the logic 7 in my 08 335i. In my 335i, i used sound settings found online that an audio engineer arrived at doing system tuning and it made a huge difference. In th emodel S, i have not been able to find settings I like and that sound good across multiple songs and types of music.
This week I had a new P100D service loaner and the stereo sounded so much better to me. I chalked it up to being a newer model, but afte being on an extended drive I pulled up the audio settings and found....all were maxed out. That is usually not a good recipe for me, but I tried it on our 12 model when i got it back and it also sounded much better to me.
Long story short...try all settings maxed and see what you think. Easy enough to revert back if you don't like it.