Magfan... You are right about the fuse. I just checked my schematic. I was going on memory from several years ago when I rebuilt my crossovers.
At work about fifteen years ago I had occasion to look into superfast fuses. These fuses would be located in test equipment and protect transistors in one assembly under test from power coming from a second assembly of the unit under test. (Missile guidance system). The only thing to blow faster than a transistor is another transistor, and that is what the superfast fuses really were. As I recall these fuses would cost about $1,000. The transistors we wanted to protect were inside a sealed gimbaled inertial measurement unit, and to tear it down, fix it, build it up again and test it would cost far more than $1000, so the superfast fuse was not completely ridiculous. In the end we didn't use the fuses. The concern was about reliability of the protected transistors if the ones in the test equipment had blown. Maybe they would still be working, but perhaps not with the extreme reliability we had to meet in the guidance system.
At work about fifteen years ago I had occasion to look into superfast fuses. These fuses would be located in test equipment and protect transistors in one assembly under test from power coming from a second assembly of the unit under test. (Missile guidance system). The only thing to blow faster than a transistor is another transistor, and that is what the superfast fuses really were. As I recall these fuses would cost about $1,000. The transistors we wanted to protect were inside a sealed gimbaled inertial measurement unit, and to tear it down, fix it, build it up again and test it would cost far more than $1000, so the superfast fuse was not completely ridiculous. In the end we didn't use the fuses. The concern was about reliability of the protected transistors if the ones in the test equipment had blown. Maybe they would still be working, but perhaps not with the extreme reliability we had to meet in the guidance system.