Yes audioexpress says the same except they calculated 7.2mmare we reading the same review?
Because the THD graph is missing
View attachment 157625
But the parting thoughts say this
"Displacement limiting numbers calculated by the Klippel analyzer using the full-range woofer criteria for Bl was XBl @ 82% (Bl dropping to 82% of its maximum value) equal to 10.2mm for the prescribed 10% distortion level. For the compliance, XC @ 75% Cms minimum was only 7.2mm, which means that for the Purifi PTT6.5X woofer, the compliance is the more limiting factor for getting to the 10% distortion level. However, if we use the less conservative 20% distortion criteria, XBl @ 70% = 11.7mm and XC @ 50% = 9.7mm, showing the Cms number closer to the driver’s physical Xmax."
When you limit the driver to 100Hz or 70 Hz it would probably hit thermal limits before distortion. But these are long throw drivers designed to be used low. The scanspeak is not.