Equalizer to the rescue!
 

Well, I finally bit the bullet and ordered an Audiocontrol EQX to fix the lack of midrange, the harsh highs and the low frequency bass farts in my wife's 98 Ranger extended cab.

I am running a PPI PCX4125 in her truck (2x 125 plus 1 x 500 watts RMS with current set up) and it powers Diamond Hex 5.25 components up front and a Diamond Audio 10inch MKII (D5) sub in a custom ported box tuned to the low 30s.

Right now, I hear almost zero speaker response from the fronts at 100 hz down. I have a set of Hex 6.5s in my car and they sound great all the way down to 60hz, but only with the help of an EQL. The EQX should help the 5.25's a lot down low. The speakers, like every speaker I've owned (Infinity, Polk, JL and Diamond) are just too harsh in the frequenies just below the crossover point into the tweeters. I can never flatten the signal out no matter how much I fuss with the HU eq settings (I tried with Kenwood Excelon, Eclipse and Clarion decks with the Eclipse giving me the best luck so far).

The lowest crossover point on the amp is around 50hz, which is great but the 12db/octave slope is too high for the inside of a truck and there too much sound coming from the sub that should come from the front speakers. The front speakers have a frequency response of 58 hz and up so I will try a 60hz crossover chip in the EQX at 24db/octave slope.

Finally, the subsonic filter (comes with a 33hz chip) should help alleviate some of the overexcursion and farting noise (for lack of a better word) coming from the sub during radio commercials and talk shows.

I can't wait to set it up - I'll let you all know how it sounds.