Audiolabyrinth, the 67000 does have a pleated surround! The 66000 did not, but the 67000 does.
Measurements I have seen show lower distortion at low frequencies for the pleated surround version of two identical woofers, one with pleated and one with rolled. It is only at higher frequencies, where folks want to run a woofer way up, that rolled surrounds were better, at a cost of higher distortion in the lows. But then rolled surrounds took over, they seemed to be looked at as the "modern, latest cool thing", even though in some models with low crossovers pleated still should have been used. If you are crossing over at 1khz or below pleated is open to you, assuming a good design. Note that on the Westminster model by Tannoy also went to pleated surrounds years back, after using rolled surrounds on that model.
Measurements I have seen show lower distortion at low frequencies for the pleated surround version of two identical woofers, one with pleated and one with rolled. It is only at higher frequencies, where folks want to run a woofer way up, that rolled surrounds were better, at a cost of higher distortion in the lows. But then rolled surrounds took over, they seemed to be looked at as the "modern, latest cool thing", even though in some models with low crossovers pleated still should have been used. If you are crossing over at 1khz or below pleated is open to you, assuming a good design. Note that on the Westminster model by Tannoy also went to pleated surrounds years back, after using rolled surrounds on that model.