For More Information

Borbely & Gaertner, "Modular Active Crossovers", Speaker Builder issue 1, 1994, p20.
Describes how to build a complete active crossover. I used the basic design described in this article, but substituted Burr Brown OPA-2604 op-amps for the discrete-component buffer circuits used by the authors. Back issues are available at AudioXpress.
Horowitz & Hill, The Art of Electronics
If you want to learn about the design, layout, or construction of electronic circuits, this is the book to read. I read the first four chapters, as well as the sections on active filters, construction, and grounding schemes, before designing and building my crossover.
Vance Dickason, The Loudspeaker Design Cookbook
Not just a collection of tables and stock loudspeaker designs (although it does have lots of useful tables), this book has a lot of information about how loudspeakers work, how loudspeakers fail (or at least fail to operate according to the models), where the tables come from, benefits and problems of all the different configurations, and subtleties of construction that are not covered in the tables. I pretty much read the whole damn thing before building my speakers.
M.E. Van Valkenburg, Analog Filter Design
This is where I learned exactly what is meant by Chebyshev, Bessel, Sub-Chebyshev, etc. This was very useful in designing the auxiliary woofer filter, but is probably not necessary if you're just doing a standard active crossover.
Articles on loudspeaker models by A.N. Thiele and Richard Small, published in Journal of the Audio Engineering Society in the early 1970s.
Dickason covers most of this in a more readable way in his book, but if you want to get into the nitty-gritty of the mathematical model, you'll have to read these. Like the active filtering textbook, I needed to know this stuff to do the auxiliary woofer filter but most people probably don't care.
Audio Electronics Links
Other web pages relating to amateur audio.

John Stimson / Art Rock Cafe, New Armageddon / john@idsfa.net