Have you sealed up the front and rear doors so that the rear wave does not cancell or interfere with the front wave? Also, it significantly reduces cone excursion and will allow for a lower crossover point.

 

No I haven't. How do you propose to do that? Is it permanent?

 

Fiberglass enclosure

 

Use a combination of asphault-based damping material (Dynamat and the like) on the metal surfaces of the door, as well as some visco-elastic (Cascade Audio V-Block and the like) spray over the Dynamat. **Don't use the Dynamat brand, though...there's a ton of imitations out there that work just as well for a lot less**

You don't have to build fiberglass enclosures to have tight midbass in the doors (although you'd get great results if you did). My method above is a lot easier, and if done correctly will not only improve midbass tremendously, but virtually elimate rattles and resonances. Check my homepage for pics. Make a mounting baffle for the 6.5s and/or the 8s out of MDF. Mount the speakers to the baffle, mount the baffle to the door. Seal the speaker baskets to the baffles with silicone (careful...may void the warranty) and seal the baffle to the doors with silicone.

While we're talking about your system...

Why do you have to have 6.5s AND 8s? If I were you I would try for a decent 3-way set consisting of a tweeter, midrange, and midbass. Having both the 6.5s and 8s seems redundant...done correctly, the 8s by themselves should more than satisfy your desires for midbass. The rear doors are a terrible place for midbass...there's too many musical cues in the midbass frequencies that are directional and should be in the same general location as your other speakers (except for the sub obviously).

Someone suggested mounting the 8s in the floors. This is not uncommon and shouldn't be dismissed without some discussion. I'm not sure if this will work in our Maximas, but if you have the room, this is NOT a totally bad idea...although not my first coice. I've never installed anything like that, but I've seen/heard them and they're as good sounding as anything else, if not better.

I honestly think you could spend forever tweaking your system with the mids in the rear doors and you will never be truly happy.

Tony