Originally Posted by Mark S.
This is PRECISELY what is happening to me now after I purchased a SVS PC-12 PLus, except when I turn up the gain the sub bottoms. I've done hours of testing/fiddling, purchased SPL meters, and gone back and forth with possible solutions with SVS tech support. They are sending me a new amp but to tell you the truth I am not overly optimistic. My Paradigm ultracube-10 outperforms it by a significant margin, and I have a hunch that it has to do with amplifier headroom (650w RMS in the ultracube, 525w RMS in the SVS).
Who knows though. Anyways, I wish you good luck, as I know EXACTLY what you are going through right now. It's very disheartening indeed. I suspect I'll be in the market for a new sub soon.
Your subwoofer is clearly not operating correctly. A properly working PC12-Plus will easily outclass the tiny Ultracube-10. I'm sorry to hear you're having issues.
The designs of the PC12-Plus and Ultracube-10 are so different that comparing their amplifier specs is meaningless. The drivers have different T/S parameters (neither driver has parameters available to the public) which will radically change their performance. The subs are different in design (ported versus passive radiators), enclosure size, driver size, amplifier (both power ratings and built-in EQ curves), etc.
Even if all other factors were equal, the difference between 525W RMS and 650W RMS is next to nothing. There would be less than a 1dB increase in output going from 525W to 650W. For any given subwoofer, DOUBLING the amplifier power only results in 3dB more output. That said, as I mentioned the two subs are so different in design that it's impossible to use amplifier power to accurately compare the two. Hopefully SVS will get your PC12-Plus up and running as it should be. The only reason I could see an Ultracube-10 besting a PC12-Plus is if you were forced to use a radically different placement with the PC12-Plus (due to its larger size) that created a huge null at your listening position. Otherwise, the performance between the two shouldn't even be close. Best of luck.