can't get sound on some games
 

I've made back ups of a few games and on some
of them (eg. Spiro 1 & 2)no sound comes through

Poor media and/or too high burning speed?

I have it set to a low burn speed, but . .. What do you mean by poor media?
I use crdwin, is this not good? Is there something else that might work better?

charlie means discs i use verbatim data life plus as far as i know thats what just about everyone else uses aswell
that should help

Another thought if your CD-R quality is good:

I don't know the games but if they use digital audio there might be issues if the burner or reader won't support that mode.

Using plug-in-mods instead of a internal modchip on a PSX will sometimes cause the audio to skip badly and the picture to distort when playing certain games.