Ya know, on the page below Ilkka mentions that the VTF-3 "Suits well for larger rooms not having much low end room gain"
but says that the PB12-NSD "Good extension and good frequency response for mid-sized and small rooms"
It sounds to me like he's making these judgments based on the frequency response of each sub.
http://www.hometheatershack.com/foru...html#post45289