Originally Posted by ben_allison
Wow what a great post! Thanks for Ning so thorough.
I'll be running a power amp and passives, so your solution sounds like a good one. I suppose I could also add the diodes for even more protection.
I just like knowing a $3000 investment isn't one small gaff away from complete destruction! lol
If you do use back-to back Zeners be sure to use high enough power ratings: a pair of 10 watt stud mounting pieces are usually enough and use a fast blow fuse before the diodes.
Power amp--> crossover-->fuse in series-->back to back Zeners in parallel with speaker driver. If you're willing to dig in to the speakers a little, connect the fuse/Zeners after the HF crossover. That allows use of a much smaller fuse than you would have use for the whole system. Average currents at mid and low frequencies are often 3X to 5X more than what the tweeter needs.
If you can stick a scope on a speaker you can get an idea of the peak to peak voltages you're seeing at your maximum normal listening levels. Obviously, you want to choose Zeners that are 5 or 10% higher voltage than any normal peaks.