There's only one other reason I can think of, and it's what all the SQ guys call "Bass up front"

Traditionally in car audio, we use a cutoff point that is far too high for the sub frequencies to not be localized. (basically anything above 75-80hz you can feel where it's coming from) Now, lower quality mids won't quite make that cutoff cleanly, and even some higher quality ones will have a hard time. So to run a dedicated midbass in that spot would make perfect sense. Sure, you can localize it, but it's right in front of you. The reflection/absorption into the floor will radiate the waves enough to make it hard to pinpoint it as the glovebox. (as long as it's not rattling like crazy)

So maybe an 8 in there to cover the frequencies between 80 and 120 wouldn't be a bad idea

 

that is a pretty good idea, since those lower frequencies are still in the mono range. now you're gettin crazy though

 

It's a mad mad mad mad mad world. I just install in it

The only potential drawback would be the need to go fully active in the XO department. Personally I'm not a big fan of multiple pre-amp signal modifications. Though I suppose to break it down into sub, midbass, midrange, and treble, you'd really need it, unless you're a real whiz with passive XO networks. In which case you could make a hell of a 3 way XO, sum the midbass channels, and send it all to the 8... which isn't a bad idea now that I think of it...

Oh man... worlds are colliding... Hank is gettin eager to install again.

 

need me to solve a circuit for you?

i can draw it out at work in about 5 minutes if you want.

 

Nah, I've got it all worked out. I just happened to have an older fully active XO kicking around from an old install of mine that I completely forgot about. (it's nice to have a closet full of amps and drivers and other bits) But if you've got experience with audio XO networks I'll keep you in mind for my next HA/HT projects.