Originally Posted by B T C
Thanks, Mike. I appreciate your input and thoughts.
I'm probably not completely ignorant in terms of understanding some of this information or being able to draw some conclusions from the graphs etc. I was a floundering physics major for a while, but that was a really, really, really long time ago. Where I am pretty much completely ignorant is knowing how to interpret the information in terms of a real world context or impact. For example, I look at those charts and I see, or think I see, that at 12.5hz the SB13 plays at 88.6 decibels vs 81.1 for the SB12? I have no idea what the 7.5 db difference would mean in terms of my home theater experience. Using Google it seems that it takes approximately a 3db change to be perceptible and that a 10db difference would seem to be "twice as loud".
Does the SB13 really play down to 10hz? SVS lists the frequency response as 20-460Hz ±3 dB. I guess I don't really know how to correctly interpret frequency response, but I did just google some stuff and I'm reading it. I've always just assumed it meant that a speaker would generate frequencies in the range listed.
You are very welcome! If you remember any of your college physics, you are ahead of me. Who knew I would actually need any of that?
The SB13 really does play down to 10Hz, but not in a way that would be perceptible to someone in a large room. In fact, below about 15Hz, most bass would be more tactile than audible, anyway. But, it's hard to get really low bass in a large room. In my first post, I mentioned room modes, which amplify bass frequencies. In my 6000^3 room, for instance, I have a 3db room mode at 20Hz, a 6db gain at 15Hz, and a 6db gain at 10Hz. (They are different modes.) But, even with my large ported subs, I don't have enough output left at 10Hz for a 6db gain to help me very much. In a small room, there might be 12db of room gain at 10Hz, and in a very small room, say 1000^3, there might be 24db. That would amplify the declining SPL from a sealed sub in a way that would make the really low bass much more meaningful.
Your room would have essentially the same amount of room gain that mine would, give or take a Hz or two. So, if you want really low bass, you are going to have to manufacture it yourself with SPL from your subs. And, that means ported subs. And, even with ported subs, such as the PB16, you are not going to get meaningful SPL below about 14Hz, or so. The reason that I use the term meaningful SPL is due to the way human hearing works. We don't hear low frequencies as well as those in the human vocal range, from about 400Hz to 4000Hz. You can Google the Equal Loudness Contours, to learn more about that.
In a nutshell, what that means, is that it takes more SPL for us to hear 20Hz than it does for us to hear 80Hz, or even 40Hz. And, in the absence of room gain to help us, we just aren't going to be able to get meaningful SPL below about 14Hz, with anything less than something like a Captivator 4000 ULF, or its smaller brother the 2400 ULF. So, if you are looking for more low bass SPL in a large room, you need large ported subs. If you are willing to compromise on the low bass, you can get by with good sealed subs. And, in the case of the SB13 Ultra, versus the PB12-NSD, that compromise will start to be significant at about 25Hz. As noted, above that frequency the SB13 will have an advantage over the ported sub.
I hope that explanation helps. The PB16 and the SB16 have been tested, and each has about 4db more output, below about 35Hz, than the comparable 13 Ultras. Above that, they are pretty equal. SVS
's newest models attempt to provide a little more low bass than the earlier Ultras. That low bass, at high SPL, is sort of the Holy Grail in modern subwoofer design, compared to subs a decade ago, where the goal was more in the 25Hz to 30Hz range, and where fairly good 20Hz SPL was considered exceptional.