There are little trick in pickup building that we've done to several Jerry Donahue instruments. We actually install a small capacitor in series with the hot output of a pickup and this can reduce bottom end in a particular pickup. With this method you can change the character of the pickup and making it sound like another. The pickup will work but the capacitor keep's the pickup from reading on a multi-meter.
Rickenbacker used a .0047 mfd. capacitor in series with the output from the bridge pickup on their 4001 bass. This is a very distinct tone Chris Squire has playing bass in the group "Yes".