I've noticed that decent car stereo systems seem to be somewhat of a
"litmus test" for home mixes I've been fiddling with. I get it to
where it sounds fine on a home stereo with fairly beefy speakers,
another one with smaller speakers, a boom box, but run it through the
car stereo with the eq flat and it sounds muddy... This seems to be
the case regardless of the vehicle or sound system. Professional
commercial CD's sound fine, so it's not the sound system.

Does anyone know something about the characteristics of typical car
systems and what it likely tells me about the problems with my mixes,
what frequency range likely needs particular attention etc.

Thanks for all input