Someone replaced the subwoofer on a jensen jps12

It can probably be fixed but it might be cheaper & quicker to just replace the amp.
Here's a little tip for you for next time.
A lot of people say a sub can be "too big" for an amp & cause it to fry (burn out) but that just isn't the case.
You can put a 50 watt amp on a 1000 watt sub & it will play just fine for years to come.
A subwoofer does not pull power from an amplifier, the amplifier puts out what it's got & the sub can either handle it or not, it's as simple as that.
In the case of a higher wattage sub & a lower wattage amp, the sub will handle it just fine.
Now, where most people mess up is the ohmage of the subwoofer vs amp.
Different subwoofers & amps have different ohmages & those ohmages come in every size ever made, so the wattage of a sub or amp has no effect on the ohmage of the product.
In case you don't know what ohms are....
Ohmage is pretty much like back pressure.
Let's do a little example here,
Let's say you need to blow threw a tube & create a nice steady stream of air (kind of like an amp pushing power threw a sub).
How's it going to work if you try blowing threw a (lower ohmage) coffee straw?
At lower levels it will be easy, but as the level of air (wattage) goes up, the harder it becomes & eventually you end up straining trying to force air threw that straw (subwoofer).
Now same scenario but this time you are blowing threw a (higher ohmage) paper towel tube.
Now you end up trying to push so much air with such little resistance that you end up straining & winded trying to keep the pressure up in the bigger tube.
You need something in between. Something that offers enough resistance but not to much. That's what ohmage is between an amplifier & a subwoofer.
Hope this helps you have a better understanding.

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