Conventional wisdom holds that tweeter diffraction effects cannot be reduced significantly with modest cabinet edge roundovers on the order of 3/4 inch.  This has not been my experience, at least not with the MBOW1.  This design, featuring the GR Research M130 woofer and the Hiquphon OW1 tweeter with 2nd order acoustic slopes, was developed using a cabinet with no roundover.  When I finally built myself a pair for demonstration purposes, I used a cabinet that had 3/4" roundovers on the top, bottom, and sides.  I kept the same crossover boards and drivers that I had used in the prototype.  I fully expected the new speakers to measure pretty much like the prototypes, which suffered from a diffraction peak at 4 kHz and a dip at 7 kHz.  But they didn't.  The diffraction problem was virtually eliminated, and the overall response was perhaps the smoothest I have seen.  Here is the response on axis and 15 degrees off axis with the original cabinet:

And here is the response at the same mic positions using the cabinets with 3/4" roundovers: