Honestly, DN, most of them are. There are many new waveforms on the XPs that are not available on the older JV series, but many of the sounds on the XP use old JV waveforms, making them partially or wholly compatible. Believe it or not, there ar4e even some waveforms in the older JV line that aren't present in the newer XP and XV series.
I have some old JV banks that were merged into one bank to fill up the 128 patches in te use bank. I'm looking for a way to now go backwards and have them as 32k files so they can be used in the older JVs. This can be done, but I forgot how to do it.
The Infamous EPU.