Fountainhead

mwhito2,
yeah an EQ would improve matters but it's difficult to find an economical one that accepts spkr level inputs. I'm sure BAF can recommend something called a "line driver", a device that takes the spkr level input and changes it to a differentially balanced output to go into various devices and it theoretically flattens out the EQ, sums L & R to make a sub channel, and various other things. They're expensive.

If your EQ in the head unit (and the -3 or -6 dB switch on the crossover) won't drop the treble content enough, you could replace the resistors that pad the tweeter in your crossover with larger resistors. All tweeters are much more efficient (louder) than mid and bass, so they're always padded down with a resistor. This resistor is before the tweeter crossover section itself, so that it doesn't change the speaker impedance the crossover parts are tuned to. If you could double or triple this resistor value you can lower the tweeter level and drop it to match your bass/door drivers. If you pop the cover off of the crossover you'll see the resistor I'm talking about. I couldn't find a schematic of the MM6501 component set.

PS: Did you check your woofer's polarity? It's easy with a 9V battery, just touch the + and - of the speaker wire to the + and - of the 9V battery, (at the crossover) and the speaker should jump out. Don't hold it forever, just long enough to make sure both door speakers move out the same direction.

Also you can try changing the polarity of the tweeters, that can affect their sound also. Just swap the wires at the crossover output. Woofer polarity is critical, it determines whether or not you can hear bass or no bass. Tweeter polarity is less critical, as long as they're both the same. As far as absolute phase....in a car speakers are having to overcome so many hurdles to begin with that won't even matter anyway. I can't think of a worse place to listen to music than a car.