We have tried to further improve the Rubanoide by using a super tweeter. This turned out to be much more difficult that we originally thought. We tried many Ribbon based designs as well as some compression drivers. They never really blended in with the fabulous Rubanoide.
Then we tried a new design that is planar membrane based and features efficiency equal to the Rubanoide's. It totally blends in, and for the first time we noticed a tremendous improvement without any drawbacks.
Due to its high impedance, we were forced to use a transformer.