it can help with midbass speakers also, but the enclosure usually needs to be fairly large in comparison to the size of the speaker as most of them are made for use in an infinite baffle situation (ie a door).
I wouldn't bother with the foam baffles. They work with keeping moisture off of your speaker but I don't think it makes the speaker sound any better. I would just put some dynamat or whatever over the speaker hole then cut out the hole and mount the speaker.