Interesting Question about a blowthrough

[truckaudioman 0]

I plan on putting 4 15" BTL's in the bed of a silverado with a blowthrough, not a wall. Out of curiosity, will there be any type of loss in pressure and sound by doin this? Also, if I make a small wall around the hole with sound deadener all under it, will that make a improvement on the loss if there will be any in the first place. I know that it will help with road noise, so i am doing it anyway, but am just curious.

[NDMstang65 403]

I've never done one without a wall...no clue man.