Actually the tweeters aren't the same. Model Five, Twelve and Twenty-Three all share the same tweeter. The Six, Seventeen and Twenty share the same tweeter but it's different from the one used in the above mentioned systems. They look identical and will measure out at the same dcr but they are sonically different and are advertised as having different cone dimensions (and damping, I suspect). If you were to swap one of them out I'll bet you'd have a hard time hearing the difference if you weren't listening for it, though. The one used in the Six, Seventeen and Twenty sounds a little less articulate and slightly "squawky" compared to the other type. The woofers, while the same diameter as the Six, are completely different. The Five, Twelve and Twenty-Three woofers (again all the same type) are much more robust and have larger magnets / voice coils and go deeper into the bass frequencies. The Twenty-Three is basically an improved Six.