ya i thought about that after i posted . air is what makes good sound i have a q-logic bandpass box and 2 12s and it is the only way to go in such a large open space. i had the same box in the trunk of my 92 cougar and it did not sound the same at all.

 

its weird how much air space makes a difference. I have 2 RF 12's, and it is so much louder and tighter sounding with all the windows up, but the moonroof open. Its like a box in a box.

 

ya porting the cab is cool. wish i had a moon roof lol

 

From what I've found, in a 2000 Blazer 4 door, the front doors can fit either a 5.25in or a 6.5in speaker. I haven't taken the panel off yet, so I haven't seen the mounting brackets, but would a 6in mtx speaker work? And is mounting depth an issue, should I be looking at a slim mount speaker?

 

I think technically the door speakers are 6.75". I bought a pair of Kenwood eXcelon KFC-X173 for my 2001 2dr and they fit perfectly. On the box they say they are "Over sized" 6.5's which may actually be 6.75", not sure why they do this. They also come with mounting brackets for larger or smaller diameter mounting screw placement. You may be able to get away with 6" as long as they come with some sort of mounting adapter.

Also, No I don't think you will run into mounting depth issues, there seems to be plenty of space in the door. The speakers I used fit just fine with a mounting depth of 2 3/16".