i used to have 2 subwoofers in a custom pored box and they sounded amazing, a mtx 8000 and an alpine type r. the mtx 8000 stopped working so i had to get a new box because the alpine couldnt push all the air right since now it had to push twice as much. my friend built me a wooden box and then he coated the inside of the box with 2 layers of fiberglass. but for some reason when the sub plays now it still wants to hit notes like it is in a ported box and not a sealed it still trys to hit the low notes and doesnt hit the high notes. is this because the box has fiberglass on it. the sub actually sounded better when it was in the big ported box by itself.