Originally Posted by drh3b
I have 2 SB-NSD. I am hitting the limiter on a semi regular basis. Will buying two more, and stacking them 2x2 bring any appreciable SPL improvement. I'm fine with the sound, just like a few more db. I can't afford the proper upgrade path of 2 S1's or 2 SB16 Ultras.
Although, buying on SB16 ultra, and stacking the NSD's with my two older Velodynes. sounds interesting if goofy looking.
I don't think it's a stupid question, or a stupid idea at all.
Adding dual SB12's to the ones you have would net you about 6db at frequencies below about 30Hz, and between about 3db and 6db throughout the passband. And, if you stacked them, in two pairs, they would net 6db more output at all frequencies. That's one approach.
A second approach would be to stack your existing SB12's, and add an SB13 Ultra. You could also try an SB16, but I think that the 13 might be a little better match. I do think that either could work with collocated SB12's, though. What I wouldn't do is to try all of that with your Velodynes in the mix. I think that the frequency response of those subs would be sufficiently different to potentially cause you problems, without some ability to measure, and to adjust the frequency response. So, I would leave the Velodynes out.
FWIW, unless you were planning to spread the subs out around a large room, I would favor adding a more powerful sub, if you can afford it. That would give you a little lower frequency response, and would move you further down the road to a dual Ultra system, at some point in the future.