Last night I finished building the box for my new sub. I got the 1 ft3 knock down box from parts Express (Link) with the Dayton Audio RSS265HO-44 10" (Link). It's being powered by the Rockford Fosgate Prime R1200-1D (Link).
I put everything in my car last night and went on a ~25 minute test drive and it sounded awesome. Today, I took a ~4 hour drive in the car, but roughly halfway through I noticed the bass was gone. I stopped at the next rest stop during the drive and after touching the cone of the subwoofer I felt that it was quite hot. The amp was even hotter, and the red light on the amp was on, indicating protect mode (overheat or short circuit).
After realizing my components were overheating, I immediately pulled the fuse from under the hood to limit any further damage. I then measured the terminals of the subwoofer, and one voice coil was measuring at ~2.1 ohms, while the other was measuring at ~1.6 ohms. Based on the resistance measurement of the subwoofer, I already know it's blown.
My main question is where do I go from here? I'm not sure what went wrong. Both the amp and sub are new -- I imagine the original problem could be a problem with either -- either the amp killed the sub or the sub was faulty to begin with.
I am quite dissapointed with this, since the sub sounded so nice while it worked. I am also quite confused since the subwoofer is rated for 600W, my amplifier can push 600W at 2 ohms (the subwoofer was wired in parallel), and the gain of the amp was around 3/11. I also don't think this is a problem with over-excursion or clipping, since the subwoofer was putting out clean sound all the way up to when it stopped. Furthermore, when I push down on the cone with on both sides, it is a firm and smooth motion just like it arrived new. It doesn't seem like there is any damage to the mechanical part of the sub, just something about the voice coils themselves.
I'm sure the quality of construction of the box was quite nice. I put a lot of effort into putting together the box, so I'm almost positive the box is not a factor.
I haven't tried to power up the sub and amp again since I am afraid that I may further damage something. I am mainly looking for advice on where to go from there.
Sorry for the wall of text, I just want to make sure I provide enough information.