I buy 2 years ago one fi ssd 12 d1 used,I realy like this sub but I want more so I order one ia 20.1 and a xcon,but when I put the sub side by side I don't see any difference,the xcon have a shim between motor and basket of 1/2 inch,the xcon weight 37.7 pounds and the fi 38.8,so I began to think is not a ssd but maybe a Q?