I'll be removing the stock plastic pods that came in my maxima and replacing them with custom mdf spacer rings. Do I need to match the height of the plastic pod which is like maybe 3 or 4 inches or will I be fine with a 1 inch MDF spacer as long as the speaker clears the window glass?

Will it sound different as opposed to me stacking 3 or 4 MDF spacer rings together?

Would this be considered a free air design?

 

it should be fine just like you said though, check the window first. you can buy baffles for the speakers (im assuming their components) but i see no need for that.

 

I wouldn't be worrying about that plastic pod. The sheet metal that it is screwed too is a FAR greater source of inefficiency.

I added a TONNE of mass and resonance absorption in the form of multiple layers of dynamat. I laid it on the inside of the exterior sheet metal, sealed all the openings with mdf, and laid two more layers on the inner sheet metal, as well as dynamat on the inside of the door skin. The small openings needed for door and lock operation were sealed with speakerfill. Essentially, I made the panel as acoustically stiff as possible, while also attempting to make the door an enclosure.

It made a HUGE difference in the midrange. It got MUCH fuller, deeper, warmer, more accurate. Saxophone, horns, vocals are VERY hard to duplicate because of the nature of their timbre. Doing what I just described will net SIGNIFICANTLY greater gains in performance over making MDF spacers. Whatever you do with the mids, make sure the speaker is mounted as rigidly as possible, with NO AIR LEAKS around the edge where it is to seal. I always use a gasket or silicone on any speaker I mount.