"Is the slowdown you are experiencing happeing at the 1.5GB position"
yes the first slow down is at the place where burn reaches 8x sometimes it reaches 8.4x and no speed up until the second slowdown; the second slow down occurs at 12x mark (with the slowed down tempo) slowing down to 8x, sometimes a slight speed up at the end to 12x but in most cases 8x 'til the end.
"Good result but at the end high TE that caused slowdown:
my scans are similar to this one a second scan (othe disk from same stack) had no peaks above 40.
now my concluding question: how can i deetermine if it's a media problem or a burner problem?
as i said before: i never had more than one in a row or at maximum 2 in a 50p stack with a straight 16x burn. i burned more than 300 disks most from verbatim 50p from maxell 16x and 50p from ricoh 16x (the worst).