the issue here is not the speakers. it's extremely common.
the reason? seals.
no, not the kind that get eaten by sharks as narrated by Sigourney Weaver.
the kind of seals created with perfectly crafted mounts and foam weatherstripping.
what you need to do is recreate the factory seals. these exist in two main locations.
1. between the woofer and the metal.
2. between the woofer and teh plastic door panel grill opening.
#2 is usually missed.
the door panel acts as the front baffle of the enclosure since the door metal has huge holes in it. the rear wave from the speaker combines with the front - cancelling it out.
midbass/bass is all about seals and isolating front from rear.