Building Passive crossovers

I've been building passive Xovers for many years.  Here's a few other pro/cons:

PRO: Generally a warmer, more natural sound can be achieved; driver inefficiencies can be corrected; complex setups can be easily created (like line arrays or multiple tweeters, etc) without multiple amps; SQ can be created that is far superior to that found in most electronic xovers; any Xover slope or Xover point can be acheived (not just factory pre-sets); does not require 12V power or remote turn-on...

CONS: You REALLY have to know what you're doing to get it right; adjusting Xover points or slopes requires removing and replacing components; can add noise or harshness if low-quality components are used; the Xover can be the limiting factor in system power handling; cannot easily swap drivers or setups without also physically re-buildig the Xover...

That being said, I prefer the sound of passive Xovers and use them in my own setups.  The notion that they can rob 50% of amplifier power is a bit extreme, but they do use some energy that would otherwise be available for the drivers.  Usually about 2% for a properly built Xover network, in my experience.

Get the Loudspeaker Cookbook for a great introduction to designing and building crossovers.