The SV12-Plus is a " Sealed Sub " which is much smaller than lets say the PB12 NSD. It is 15" front to back while the PB12 NSD is 25". It weighs 40 lbs compared to the PB12 NSD at 74 Lbs. The SV12 Plus has a different woofer and is rated at 450 watts compared to the PB12 NSD at 325 watts. Having said that ,the Pb12 NSD is a lot more powerful and goes much lower due to its much larger internal volume and lower tune ( A hugh advantage for Movies ) The +/- 3 db rating for the SV12 plus is 22hz compared to the NSD at 18 Hz ( In room extention can be another 3 db lower and the design of the NSD will get you down to 15 Hz in an average size room ) For music the Sv12 Plus MAY be slightly better, but then again it can't go as low ( So pipe organ sound and other lower notes will be picked up better with the NSD ). The PB12 nsd is a better performer than the 10" model although that one is also highly rated as well. For the price difference I would go with the 12" NSD model if you chose the " Ported Sub Design ".
