Maybe I missed it in a previous thread, but what is this crossover mod I keep hearing about for the Avatar cabs? How is it wired, what does it do, and where do you buy parts? If there is a weak point on these great cabs, it is the crossover. Just got my 2X10 and 1X15 this week, so is the mod necessary on my cabs, or does it just need to be done on the older ones? Thanks!!