I'm new to Polk and to forums but just needed some help here. I bought a pair of Rti12s new from Polk audio direct and got them setup and plugged into my emotiva XPA 5 with 200 wpc with my Onkyo TX-NR809 doing the processing. At reference volume the top woofer will rattle as if a piece of plastic is hitting in the center of the speaker. I removed the woofer to see if anything was hitting it like wires but nothing was. Is it blown? it doesn't scrap when when you move the woofer by hand. So I'm not sure what the issue may be. Any ideas?