Alright, since there's a little room for improvement when it comes to getting better sound out of your 6x9's, why not do it.

My question is since the "Enclosures" are made of some sort of insulation material, what other ways are there to make them sturdier, WITHOUT fiberglassing them?

I was thinking of covering up those holes with something and then spraying it with multiple coats of rubber undercoating? I think enough coats of the stuff would work.

Two more questions, WHAT would I cover those holes with? and How do i remove the metal plates that the speakers are screwed into?

 

The metal plates are held in with screws. I sprayed mine with a few coats of rubberized undercoating as well, you will be happy with the difference. I also replaced the metal plate with a plate made of 3/4" MDF and it made a difference.

 

I had some Boston 6 1/2" speakers lying around so I used those instead of my JL 6x9". The tweeter was rattling in one of them so I decided to use the Bostons for now. I used I think 1/8" or 1/4" MDF and placed that over the metal.

 

the biggest deal is NOT where the 6x9 mounts, it's the outer skin on the car, and all the plastic panels that the 6x9 can vibrate.

your best bet is to seal off the 6x9 compartment, while leaving it as large as you possibly can...

most people just toss in some cheap-o 10" sub or something, because it will be cheaper and easier...