So, I read in a post on here (Youtube) that the bass from the 5 1/4" was due to the box being long which gives off the resonance. I have an access cab, in that little storage area where the jack and tire iron is, would it be okay if I made something like this but with 6.5" subs in there? do I need to have a vent? will it work better or just the same with/without the port? Not being in an open area like in the video, will being in an enclosed area lower the bass response? if you add in say three more 6.5" subs, will this shorten the resonance the box will be projecting if it had only one sub?