You would notice a big difference by sealing the inside wall of the door. The front and back of a speaker both produce sound, but it is 180 degrees out of phase with each other and will cancel each other out. That is one of the reasons speakers need enclosures, even Infinite baffle drivers most found in car audio need a baffle to separate the sound from the front of the speaker.
Also if one speaker was out of phase with the other it would cancel the other out, but the back side of driver A would be in phase with the front side of driver B, and vice versa. It might cause the sound to be most proponent behind the speakers.
The stock speakers have little plugs on them so they wouldn't be out of phase, unless an aftermarket headunit was wired wrong.
Also if one speaker was out of phase with the other it would cancel the other out, but the back side of driver A would be in phase with the front side of driver B, and vice versa. It might cause the sound to be most proponent behind the speakers.
The stock speakers have little plugs on them so they wouldn't be out of phase, unless an aftermarket headunit was wired wrong.