Sloped baffle

It is used to time align the drivers. Some manufacturers do this physically, (with the cabinet) and some do it electronically (in the crossover).

Just a different means to an end. You can have good or bad sound with either arrangement. One way isn't necessarily better than the other...

There is a really good book that explains a lot of this and is written for the person without a PHD. It's entitled "The Loudspeaker Design Cookbook".

I pulled my copy out and reread some of what was discussed above. I highly recommend it if anyone is interested in loudspeakers and how/why they work.