I'd like to point out to you guys, with Dynamat (or similar products, though I haven't used them) it's not reducing road noise that is making your speakers better because you can hear them over the road.. it is LITERALLY changing the way your speakers act, because you're creating a box within the door, the speaker physically moves and because of this it is moving air in front of and behind it... this movement and bass causes the panel to vibrate, by layering the whole door with Dynamat you're reducting the physical energy (vibration) which reduces the sound of distortion coming from the panels it's self and rattles. ON TOP OF THAT.. now that the door is more sealed than previously your door ends up serving a similar purpose as a subwoofer box would. So, what you get is an increased level of bass return to cabin, also CLEANER and more ACCURATE. Because the speaker is acting more effeciently it will sound louder.
Vibration, Sound, road noise.. win