Points made above are correct. To be blunt, the Polk PSW10 is one of the least impressive subs available mass market. I had one and know exactly how it sounds. One thing you can do to help matters is get the sub out of the corner. Corner loading increases the output and is likely exacerbating the problem. DO a sub crawl and find the best place for this sub that is NOT a corner.
Subs>RBH I-12e, I-12. HSU VTF-15H mk2. Monolith THX 12(x2), THX 10(x2). XTZ 1X12. SVS PB-1000(x2). Speakers>JBL Studio 270/235c/230/225c. Sony CS3/CS8/CS5. QA 3020i/3090Ci, 2020i/2000c. Monolith Cinema 5bs. Polk RTiA1/CSiA4. Other Audio>Sony MDR-Z7m2,V6, XB900n,700,XB32,XB31. Sennheiser HD58X,HD4.50,PC37X. HiFiMAN HE4XX. Philips SHP9500. SIVGA SV004. SA HDTwo. HyperX CloudPS4. TB Elite AtlasAero. LG FH6,RK8,RK7,PK5. HK Onyx Studio4(x2).