chevy cobalt speaker install problem?

[Master chiefer]

i put some alpine type s 6 1/2s in my cobalt doors. the stock speakers had an airtight seal around the openings, and the cutout is oddly shaped. with the alpines in the doors, there are spaces around the speaker and the opening. is it necessary to seal the gaps for an airtight seal? will it improve bass response? the bass is kinda weak. and if i should try to seal the gaps, how should i go about doing it? im not too great at custom installs, so preferably an easy fix? thanks

 

[Lance]

I would put dynamat behind the speakers, and you may be able to seal the openings with that too... another thing you might try is foam rubber speaker baffles things that you can install that may be large enough to seal the opening, they have a flange and a foam cone that goes behind the speaker, it give it a seal