What's wrong with my NEW sub?
 

For starters, I built a "stealth" box for a 10" Kicker CVR @ 4 ohms. It turns out the box was too small and I fried 3 subs in less than a year.

So I decided to upgrade the sub to a 10" Kicker CVX @ 4 ohms and had a ported box built that sits on top of the shelf in the trunk.

Well today I installed it and I can only turn the volume up about half way before I get this horrible rattle from the sub.

I played with the amp and turned the settings down, etc. I know a ported box has to be tuned differently than a sealed box, but it's NO WHERE near as loud as the small sealed box and I get that rattle noise.

Only thing I can think of is that I didn't "blurp" the speaker before installing, but I don't think that will fix anything... Any clues?

Oh and I'm running a JL Audio 250.1 amp.... not the slash series.

Really? No one can figure anything out?

Here's more information concerning box...

I did the math and the box is .25 ft^3 larger than the maximum vented enclosure for the sub and the port is half as large as it should be.

My thinking is that I could make a brick of wood that would be the same as .25 ft^3 to fasten inside and then open up the port some more. Would that method work and can it make THAT big of a difference? I would hate to do the work for little to no outcome.

Again I was running the amp at 2 ohms (4 ohm DVC wired parallel) and the sub was what sounded like bottoming out at a very low volume. I changed the sub to run at 8 ohms by wiring it in a series and the noise went away, BUT obviously the travel of a sub at 8 ohms is very weak... the system sounds decent at best inside the car and barely noticable outside the car.