Got 2 PT15D4. When both were wired together at 1Ohm, they both made a rattle noise before it put amp in protect mode. So, I wired each one individually and it only did this with one sub.
The sub that does this has no visible sign of being blown, nor does it sound or feel like its blown when I push the cone down. The voice coils still read 4Ohm each. What could be the problem with the sub? It plays and sounds fine, but once it starts to make this rattle noise it sends my amp in protect mode (well it did before it caused the amp to blow).