15 inch jl audio d2 ohm sub

Chances are that the wires have been broken off, much like if you take a piece of wire and bend in back and forth a number of times, eventually it heats up and breaks. With you running power through these small tinsel leads that is causing the driver to move, here lies the problem. My guess is that you have one of the following problems.

(1) Your gain is set too high on the amp which is causing the driver to move in and out more than it was designed for, when the tinsel lead reaches or nears it's maximum length and the speaker cone still wants to go more, one of the two is going to win this battle. Once the leads have broken and you resolder them in, now the leads are a little bit shorter again, and the problem will arise again.

(2) The subs tinsel leads came from the factory at too short a length, again the same problem will happen, maybe not due to due to the amplifier gain this time, a factory defect. You resolder them and they get shorter and they break again.

In order to solve this problem if this is the problem, a new sub or new tinsel leads (which usually means new sub) are probably in your future. Sorry for the bad news if this is the problem.

I would guess that it is one of the two options that forbidden provides, except one thing.  It might not be due to the gains set too high.  Is the sub in a ported enclosure?  Playing frequencies below tuning on a ported enclosure will cause the cone to go too far and break tinsel leads (and other things depending on design).  But either way you are pushing the sub too hard.  If you do have a ported enclosure, I suggest you get a subsonic filter and set it at your tuning frequency.  You could also have too much power for the enclosure used, or as forbidden said, have the gains turned up too high.  Either way you have a problem, and if you don't fix it soon your surround will go next.

I would suggest contacting your local JL dealer and see how much a recone on the sub would be.  It may be cheaper than buying a new one.