My observations: * Some optical drives read a CD-R better than a factory-made CD with a similar amount of damage. (CD-R's only have ~70% reflectivity) * When underclocking the potentiometer (at the optical pickup unit) of an old 2003 optical drive (HL-DT-ST DVD-ROM drive, forgot model number), it might cause CD-RWs (~25% reflectivity) to be undetectable, but actually improves the reading performance of a damaged factory-made CD! * The optical drive from 2003 can read damaged CDs and CD-Rs (CD-RW untested) better at high rotation speed. Although with a lower DAE (digital audio extraction) quality, it does not get stuck like it does on low speeds (hanging and hickup sounds). * A data CD-R with a small hole in it is still 100% readable (thanks to error correction) at high speeds, but not at low speeds. The opposite should be the case. In different cases, damaged discs (especially DVDs) were more readable at low speeds, but these cases from above are still strange.