Re: Frankensub - a cheap Edge meets a marginally less cheap GT5
No one can tell you if the sub you installed will work well without knowing the specs of the box and the sub that was in it. It could be that the JBL sub is a good match for that box and it could be the opposite but mounting depth is not an indicator.
Ultimately, if the JBL sub sounds good to you then it will work just fine. But the thing that worries me is your comment about turning the gain down to half way for break in. Unless you're running a line out converter from a factory head unit or you have an aftermarket head unit with very low preamp voltage... your gain was and still is too high.
Gain is not a volume control to be set to preference. It is a voltage matching pot that should be set when the amp is installed and not changed. Chances are that your gain setting is the cause of your original sub's death and if you don't address the problem now, you'll wind up with another dead sub.
As for the "break in" period... it's not something you have to do. A speaker's suspension will loosen up after ~8 hours of play time and that's going to happen whether you want it to or not. Going easy on the sub will make it take longer to break in but it won't help the sub live longer or sound better at all. Assuming you have a clean signal, play it the first time like you plan to play it after the "break in" period. It will either break or it will work. If it breaks, there's a defect and you want to know that sooner rather than later.
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