Either you like more bass than usual, or there is a problem with the car's system. Sometimes the speaker polarity is connected wrong and that kills the bass. Anyway, I have unbolted the subwoofer but have never tried the system with it disconnected, but I too think it won't work like that.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.