Originally Posted by coolcat4843
Always go with dual subwoofers.
You'll get smoother bass response and help combating standing waves in your room.
IMHO, it is not as simple as this. What if you only have 2 placement options and they do not give a good combined response? What if you don't have measurement gear to assist with the integration? There are rooms where a single sub can give a very good response. This is a single submersive in my room with no smoothing (60hz crossover)
When deciding on a subwoofer purchase, I think it is not only important to determine your current goals and what is most important to you (output, extension, size / WAF, response over multiple seats, features, etc.) but also try to figure out your future goals. When I was looking into a sub upgrade, my original plan was to get dual ~$1000 subs. After thinking about it, I realized that I would probably want to eventually upgrade again in a couple years. So I went with a one more expensive sub, instead of less expensive duals, with the plan to add a second later.
For the OPs original choices.
Not sure which SVS Ultra you were looking at. The title says PB13 but your post says SB13.
SB13 Ultra: Will have the least output, especially from 15hz to 30hz, but is the smallest so has the most WAF. It would also allow for the most flexibility in placement.
PB13 Ultra: Multiple tuning options give a lot of flexibility. Lower extension then PB12. Around tuning point, close to the output of the Submersive. Multiple people have commented that a single submersive is considerably better.
dual PB12-Plus: Again, multiple tuning options give a lot of flexibility. Potential for smoothest FR, especially across multiple seats. Except for deepest frequencies, probably similar output to a single PB13 Ultra.
submersive hp: I am biased because I own two, but probably has the most output at all frequencies. Widely considered to be one of the best individual production subs. Other then going DIY, very few people upgrade to a different sub.
The Rythmik and PSA subs are also great choices.
If you are willing to take the time, buying measurement gear can also offer significant improvements.
As I said earlier, try to determine your current goals, your priorities and possible future upgrades. Also, see if there is anyone local where you could see and hear the subs in person. Lastly, give each company (SVS, Seaton, PSA, HSU, JTR, Rhythmik) a call and discuss your situation. Sometimes a simple phone call can help you make a decision.