external speakers on G4

[CC]

I had a set of external speakers that I used with my Beige G3.
I packed them up when I got the G4.

I wonder...Would these work with the apple speaker line out of my new G4?
I had heard that you couldn't use the older speakers, but I don't really know why?
Have they changed something that requires you to buy a new set of speakers.

The Harmon Kardon speakers set look and sound geat, but I dont want to have to buy them if the old set could work.
thanks... C.C.