[imcarthur]

As Jeremy pointed out, car doors don't seal well. I dyna'd the whole interior door surface & most of the outer (inside the door). You might try putting some loose fill (synthetic pillow stuffing) behind each midbass & bass driver. That helped my install with lower mid articulation.

Even without the subs (dual 8" drivers in the typical rear seatwell with 600 watt mono), my door speakers (Focal *) did a reasonable job down to 80 Hz or so. Maybe the Dyns are too forward in the upper mid & highs. Try an upper cut rather than a bottom boost. Often a tilted frequency response makes you assume the opposite of the real problem.

Ian

* Disclaimer: I sell Focal home & Pro. I am biased.