If a chemical strong enough and/or exposed long enough to soften/degrade the chemical(s) impregnated under pressure into the paper, but normally it would be an indication of a damaged or torn loose spider.

Yeah, the pair we put in the A7s had to be rotated as often as the 515s and they looked well used after ~ 3.5 years of high power 'sub' duty before we moved away, but still performed up to par AFAIK, though without doing comparison distortion measurements there's no way to know for sure.

While I agree with you in principle, the reality with this driver's original surround is that it was so flimsy it didn't hold its form well, at least after being shipped cross country, whether in a box or mounted in a speaker. You can see in this picture that the surround's shadowing shows an anything but uniform contour once installed: http://www.lansingheritage.org/image...ome/page04.jpg

Never have heard why the swap to foam surrounds came about since they performed fine, but we assumed it was a cost reduction issue, though the distributor's in-house speaker designer commented that the foam surround version sounded a bit flat/dull to him, so may have also been to at pander to the then new shift to a more recessed mids/lower treble in HIFI/studio monitor design.

For sure, my first/only impressions of the foam surround 848 and 9846 left a lot to be desired, though at the time I wrote it off as being mostly due to its much lower efficiency/increased distortion at the ~live piano bar SPLs I normally listened at, so don't know if the foam affected this or not.

Never having any interest in the 411s for other than the one 'sub' duty app, I didn't bother with keeping current WRT any 'updates'/differences, but my limited experience with foam up to that point was to avoid it like the plague. Today's foam is fine and maintenance free, so would be my choice for a < 500 Hz XO app, though without auditioning a GPA re-cone in an 848 or similar, my 'knee-jerk' reaction is it still won't perform well enough for me with higher XO points.

GM