Mine was rattling at any sort of decent volume and was going to replace it because of this. Then discovered sicklaser's post and sure enough the dust cap was loose so I just removed it and now I can enjoy my "premium" sound system once again. I do plan on dynamatting the parcel shelf and probably getting a not-so-expensive sub to replace the weak factory sub in the not so distant future but for the time being this is a good quick fix for me. Cheers, Mat J