Seeing how the SE/30 is basically a Mac IIx stuffed in a compact case, I don't think it's likely there have ever been SE/30's with the classic chime. More likely you didn't make any real distinction between the different chime sounds years ago, which is why in your memories they all sounded the same. It's quite easy to understand how someone might not notice the difference in sound quality, if you're not all that interested in the technical details of the machines.