First Order Crossovers: Pros and Cons


I wonder if some folks might share their expertise on the question of crossover design. I'm coming around to the view that this is perhaps the most significant element of speaker design yet I really know very little about it and don't really understand the basic principles. Several of the speakers I have heard in my quest for full range floorstanders are "first order" designs. I have really enjoyed their sound but do not know if this is attributable primarily to the crossover design or to a combination of other factors as well. In addition, I have heard that, for example, because of the use of this crossover configuration on the Vandersteen 5 one has to sit at least 10 feet away from the speakers in order for the drivers to properly mesh. Is this really true and if so why? Another brand also in contention is the Fried Studio 7 which also uses a first order design. Same issue? Could someone share in laymans terms the basic principles of crossover design and indicate the advantages and disadvantages of each. Also, what designers are making intelligent choices in trying to work around the problems associated with crossover design? Thanks for your input.
dodgealum
Post removed 
Viridian. Your explanation is helpful but leaves me wondering--Why would a speaker designer want to allow each driver in, say, a three way design want to "bleed" into the frequency spectrum of the nearby driver(s) rather than use a steep slope (is this sometimes called a third or fourth order crossover? I need help with the terminologies!) to prevent interference between them? What is to be gained from using first order designs that allow the bleeding to take place? Do the advantages of the first order design depend upon drivers of sufficient quality to be able to blend accurately? Which of the designers using first order designs do the best job getting the blending to occur seemlessly? Sorry for all the questions but your post raised more questions for me than answers gave!
I don't have the technical chops to make a great contribution to this discussion, but my understanding is this: first-order crossovers confer benefits in terms of maintaining phase accuracy (coherency?) across the drivers. The price for doing this is as Vridian stated, the need to have all the drivers operate well beyond their prime frequency range. Which means that driver selection becomes especially challenging.

And why would you want to maintain phase coherency? I'll leave that for someone else.

Great thread, Dodge.
Ahhh, but it would seem you do have the phase chops for this Drubin...coherency (is that how it's spelled?) is what we are all after and why some turn to single driver systems...they can hear the X-over.

Dave