I would add some type of ballast/solid filler in the 1.75cf box so its the same size as the 1.25cf box, or the dynamics of the two speakers will be off and it will sound weird/cancel, the increase in volume is ~30%, a big difference

 

Thanks, I'll definately look into that.

 

looks good

 

Did a test fit tonight to make sure everything was fitting properly after the first layer of glass was layed on top and it does and I'm very happy with that.

 

What would you suggest as material for the fill?

 

fiberglassed MDF, or just keep adding a bunch of layers of fiberglass to the inside of the box. I would make a rough cutout of the bottom in MDF and then fiberglass that piece into the box, and then fiberglass some of the sides. You can also use expanding foam to fill some of the corners and then fiberglass over them as well. The key is to make sure there aren't any leaks into those areas

 

Thanks!!

 

You can just make a couple MDF cubes to get up to the area you want and use liquid nails to adhere them inside.