First of all, the PB-3000 is tuned more deeply than the Klipsch sub. The SVS subs have very aggressive high-pass filters that limit what they can do below port tuning. Klipsch allows their sub to have output below port tuning- it's hard for them not to since they use an analog amp- but the output below port tuning is largely gibberish and distortion. The stuff it is doing below port tuning doesn't matter. It will sound terrible in that range and shouldn't be considered usable output because it wouldn't be close to being clean.
Second, that sweep is taken at a nominal output level. I would bet that is the maximum output for deep frequencies for the Klipsch sub, even though the input signal wasn't very high. Turn up the gain in that system and the deep bass output for the PB-3000 will just keep going up, but not so for the Klipsch. It will compress deep bass output much more rapidly. Take a look at the CEA-2010 numbers for 20 Hz: Klipsch at
99.7 dB, PB-3000 at
108.3 dB. That is a 3X difference in deep bass output capability!
Perceptually the PB-3000 will sound a lot more deep bass heavy than the Klipsch sub. Turn on a movie with lots of deep bass, like the pods rising scene from War of the Worlds, and the PB-3000 will add a lot more weight to that scene. I didn't watch Youthman's entire video, so I don't know if he added that kind of context, but context matters here. I suppose you could argue that the Klipsch subs have more extension, but only on a technicality, not for practical purposes. The question of extension is not even close in reality.
