You could just build a hole in the wall that will give it plenty of airspace and not cover it up. Not exactly what you want but do you want bass still or do you want to spend a lot of money and do it right?
butter and jelly please.
Home theater gladly not designed by ereed or bgtighe23. 65" JS9500, Marantz 7702MKII, Parasound Halo A31, ClassDaudio SDS470 4ch, RBH R56, 4xRBH R55, 2x RBH R5, Hsu VTF 2 MK 3 and VTF 3 for subwoofage, OnStage MS7701B mic stand with boom for improved Audussey XT32 calibrations. Listening space happily treated with 1" OC 703 rigid fiberglass. OPPO 203 or 205 soon.