Hi, This is a newbie question seeking help and info. I wanted to get opinions on how to tune (change mass load) a passive radiator on a VMPS subwoofer which has a 12 inch active and 15 inch passive radiator in a sealed box. Any guidance, pointers, advice to do it the right way would be appreciated. Also curious if people had any thoughts on VMPS subwoofers in general. This is DIY forum, but VMPS does sell kits and so was wondering if any other users had any experience. Thanks.