I asked this question on DIYMA once and didn't really get a satisfactory answer.
Generally if I model a mid-range, it seems that an enclosure makes no difference when you are crossing well above FS.
So in a typical automobile install where I want to run it 300Hz and above, does enclosing (sealing) it make a difference vs venting it into the a-pillar or down into the dash with a nice load of foam ?
For example I have mine in large pods, the pod is not airtight, but the backwave has to travel through the back of the pod down into the a-pillar and dash and I have a lot of acoustic foam stuffed back in there.
In my car they are dash mounted (up firing) and vent through an impenetrable mass of air ducts, wiring, and structure. In both cases they are crossed above 300.
Most high end installs I've seen do seal them up and try to get even as much as 1 liter for a 4-5".
Is there something to be gained by sealing my mids given the frequency range used ?