Woofers and Trunks

Dudes-

I have noticed in the last few years that vehicle manufacturers are making much better seals between the trunk space and passenger space of their cars. This is good for road noise reduction, but not good for someone who puts a sub in their trunk and wants to hear it. In my car, I have to fold down the seat in order to get the true bass response I want. It literally is about 3 db louder with the seat open. My 1984 Honda Prelude, back in the day, hit hard no matter what position the seat was in.

Has anyone else noticed this? How can this be gotten around?

I even went as far as removing the full range speakers from rear deck, leaving the grills there. I was hoping this would vent the bass into the car. It made a bit of difference, but I don't consider it a solution because I have no rear fill for mids and highs.

I also thought about a bandpass enclosure, vented right into the interior with a duct in the rear deck. Problem is, I like the accurate bass of a sealed enclosure. Bandpass is way to sloppy and "one note" for my taste.

I have noticed this in many cars, saturns, neons, mazdas, etc.

Is there an answer here, or do I just have to live with limited bass with the seat up?

Fabricate an enclosure that has the subs on the back dash and the box underneath it. This would require you to refabrivate the entire rear protion of the back dash area, but this will eliminate the problem that you have.

This is a very subjective issue given every cars and subwoofer has different  acousticst. 

 As example, I have a small "packaged" JVC subwoofer which I've used in several cars, usually under the passenger seat (t's a passive dual voice coil model, I drive it with a 2x30 amp).   In that position, the low bass it created was O.K., but nothing to get excited about.  However, I just put it in the trunk of a 1998 Pontiac Sunfire, and even though I was concerned that its sound would be "buried" behind the back seat, boy was I wrong - that  thing kicks now.