My 2002 Tundra rear doors are creating a box-y resonance in the lower mids (JL 6.5 co-ax). I am using dynamat door kit and speaker kit together,and will be adding an additional layer to try to kill the harmonic coloration from the plastic door panels. Since these rear doors have no operating windows, would stuffing them with some sort of sound deadening material tighten things up?
try using the spray/paint in liner, I forget the name. it's a bed liner material you get in a gallon container.. use that on the sheet metal behind teh speakers inside the body.. that'll change and lower the symathetic freq of the vehicle around the speakers there otherwise give thought to a 1/3 octave or parametric EQ to help shape the sound as well
I'll try more Dynamat first. This time on the interior of the plastic door panel/ enclosure. Seems that's where the biggest problem is. I'll test run some analysis tones and then see if I can tame the box-y rumbling with crossover adjustment. I don't know if the paint on material will dampen the plastic enough. I'm tempted to put some open cell weatherstripping foam between the metal and panel contact points, but I'm not sure that's where the problem is. Does anyone have experience with this situation?