My experience was that that 20x was rare using the internal B2 drive. 4 to 6 was common, but I also had quite a lot around 10x.
I used an external CD drive sometimes, which was significantly faster, and ripped the last few hundred CDs to my laptop, with the benefits of faster speeds and being able to rip direct to FLAC, so no compression time later after loading to the B2.
I don't know of any way to speed up ripping other than the above: my impression is that it's probably more to do with the characteristics of the CD than the B2. Others here will no doubt know a lot more.