Hello...i'm using a small polk sub with a rear port. i have it situated a few inches from a side wall and about 3.5 feet from the corner. i've noticed if i go behind the sub there is a lot of muffled base. i'm wondering if this is normal for a sub with rear port or if it is a location problem. it seems most of the newer subs have the port on the front so i'm thinking a rear port is no longer considered practical. i would appreciate your thoughts on this.