> Cd reading ratings are not entirely accurate. The 48 speed quoted is the
> theoretical maximum which is on possible at the very last part of the disc where
> the disc has a larger diametre and more data passed under the head in a given
> revolution. Most drives start slower and build up as the drive head moves
> towards the outside of the cd.
>
> Also some drives read cdr media or media that it has trouble reading at a slower
> speed to increase accuracy.

Correct!

I have an Afreey 56x IDE CD-ROM that I use for a ripper, and even though it is one of the fastest CD readers that I've ever used or seen, it also only starts reading at somewhere between 20x and 24x, and only reaches maximum speed (56X) at the very end of the disc.

So having a 48x (max) CD-ROM start reading at 20x, is perfectly normal.

Download CDSpeed from http://www.cdspeed2000.com/ , and benchmark your drive. Best to use several CDs, some pressed, some burned, maybe a CD-RW or two, and see how your drive reads them, and at what speeds. Even though my drive can read pressed and burned CDs at 56x (max), it only reads CD-RWs at a fixed speed of 8x.