Q: Open YouTube & play 'SMPTE jazz'. You'll figure it out.  It's considerably affecting your work...your coolest basslines fall flat on the leveling below 100hz
A: how would it effect my work if i did not even car check it until it was done, at which time i actually raised the bass drastically because the car test is actually what revealed that the new bass sounds actually had way too LITTLE low. so i raised it considerably after that. in fact, my car system on some bass sounds gives me nothing below the low F. so what you are saying is mostly the opposite. people often say the bass is too overblown. but perhaps you could send me some examples of mixes you have done because i am curious to see how the pros are doing it