I agree the culprit is much more likely to be unbalanced vs. not flat. The principle is no different from what you face with car tires. Which begs the question of could there be such a service as a "CD balancing " service" and would it be practical.
CD player vibration from CD's
I was changing a cd and noticed a strong vibration in my Oppo BD83SE cd player. I have had quite a few cd players and have never noticed this kind of vibration before. I found it was not caused by all cd's. With some, the majority, there is very little or no vibration. I am assuming the cd's in question are not round. Anyone else have this happen with your players? I am especially interested in Oppo Players but anyone feel free to chime in.