The low end is always the hardest part. Usually, the car test has the opposite effect...bass that sounds decent on the monitors can be overbearingly loud in the car, because cars are just big bass chambers. Having said that, the biggest problem MOST people have is not really with the lows (stuff below 100Hz), but it's more with the low mids...that huge area between 125Hz-500hz is where I spend 95% of my mix time trying to get balanced. The line between "warmth" and "mud" is just very fine when you're talking about people playing your tunes on ALL KINDS of different systems.
I really don't think the low end is out of hand on this tune...it's a different KIND of low end than exists in most pop/blues/or country mixes...hip hoppish stuff is SUPPOSED to have a lot of stuff below 80Hz in it, and since most of use can't even hear stuff below about 30Hz, you have to use your body as your guide, lol. Turn it up as loud as you can stand it on your monitors and leave the room and feel it. Switch between your mix and a commercial mix AT THE SAME VOLUME and leave the room during each and get that feel of where one is lacking. MOST times, when I do this, my mix is boomier than the commercial mix I'm A/Bing with.
Having said all of that crap, the truth is that most people in the real world listen to music in their cars a lot more than they do on quality home playback systems. Get it sounding good in the car, (be sure to check it on computer speaks [which have no low end at all in them] and make sure nothing out of whack is happening on either.
Besides the car, computer speakers are how most normal people hear music these days. It's a sad reality, lol. This'll sound insane, but computer speakers make for A GREAT bass check; when you listen on computer speakers, see if you can HEAR the notes of the bass. If not, it's not loud enough or it needs more midrange in the bass. You can't MIX on computer speakers because you might blow out everybody's subs if you were to rely on them for checking actual bass frequencies, but when trying to get the BALANCE of the mix, they're very useful.
I typed a lot and probably didn't help at all. MY biggest aids when mixing bass are good reference mixes and the volume knob. Between sounding good on your monitors and in the car, go for the car.
