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

Showing 4 responses by dodgealum

Songwriter, thanks for alerting me to the earlier forum discussion. I see now that this is really much deeper than I had anticipated. We have a full throated ideological struggle going on relative to this topic. Though I learned much from the discussion I still feel ignorant of some of the basic concepts and terminology. For example, Jeff Joseph's contributions on the benefits of steep slope crossovers seem pretty compelling--why would you want a driver to operate outside the frequency band it is best suited to reproduce? It seems that phase coherency is the primary benefit of a 6db per octave design but I cannot determine the value of this since I'm not really sure what "phase coherency" means. Can anyone enlighten me and discuss why this is so important?
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!
Viridian. You are no doubt correct. My reference to Joseph's "contribution" was to the thread, not the technology.
Not sure if anyone is still paying attention here but I was just reading a review of the PMC OB1 loudspeaker in which the reviewer states that the crossover is wonderfully designed and produced a plot of phase coherence that is the best he has ever seen. According to the review, the crossover maintains the drivers in perfect phase with each other except for a small abberation at one point in the frequency spectrum. Given all that has been stated above by the first order crowd, how can this be given the use of 24db fourth order slopes? I'm sure I'm missing something here as this discussion lost me a long time ago. I'm just wondering how a steep slope design like the one in the OB1 can produce such perfect phase relationships as measured in the review.