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.
"Time/phase coherance"
As Viridian notes above, 1st order helps with phase. However, it's one thing to time align the drive units & anther thing to tackle electrical phase. Cheers
Darn, Marty, apart from the humor you so graciously provide to us all, you've conferred a tremendous amount of good information in this thread.

Not much I can add beyond saying that the more complex the crossover becomes, the more oomph an amp must have to push the music through these parts.
Richard Hardesty is a big advocate for 1st order crossover speakers. You can visit the to read more. Like Viridian was saying above it appears to take about 8' to 10' for first order speakers to intergrate.
6moons did a piece on the Green Mountan Continuum last November, which is rich with discussion of these issues. One of the best audio articles I've read. Read it here.
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