@paul6001 Sorry that I derailed your thread with Kenjit, but overall and I can tell you that a handful of people that gave you answers had a very good understanding and gave accurate answers. It looks to me that regardless of the many answers, most concur. The speed of sound makes all frequencies travel at the same speed regardless of wavelength. Phasing does matter to some degree, but is not the be all end all.
I can tell you that there are differences. I have taken a nice 2way out of a standard type of cabinet and switched it to a sloped front cabinet. To be fair, also changed the crossover a bit to compensate for listening angle at the seating position, but in the end. I was able to add depth to the soundstage as well as a more pinpoint placement of instruments... Overall, in some speakers, it may not be dramatic, but in others, depending on design, it very well could be. Good luck, I hope this helps in some way, Tim