This thread on stereo and bass issues has moved me to quickly describe my 
solution which has resulted in many hours of intense pleasure, brought me 
closer to many intelligent forms of wild life, added several mph to my high 
efficiency cruising speeds and seriously enhanced my skills at hiding 
Internet purchases from SWMBO. 

Long ago I became depressed with the sound quality of the stock system. 
Finally, not able to stand the distortion any longer (or the audio disdain 
projected by my children after they passed the age of 3, I had to act. My 
major modifications including the addition of a subwoofer are detailed in the 
archives. But I will summarize in the following. 

I removed the stock Blaupunkt speakers (they prove that even reputable front 
line audio companies will do anything for a few DM) and Dremeled out the 
speaker from the grill. In the rear (Westfalia), I mounted a set of 5.25 inch 
Boston Acoustics in a small baffle box, connected to the stock grills. In the 
front, the same B/A's but with the B/A grills which I cut on a lathe to a 
fraction of their former thickness to clear the dash. Modified the 
windowcranks to clear the 0.125 inch projection. I then added a set of high 
end 6 x 9 Blaupunkt 3-ways to the lower portion of the doors (clearing the 
map pocket so that the speaker grill just penetrated the underside). I also 
added a set of the 6 x 9 Blaupunkt 3 ways to the rear storage box (beneath 
seat) using spacer rings so I didn't penetrate into the storage volume with 
the rear of the speaker. 

A subwoofer is essential, so I made a sealed box for an 8 inch Pioneer 
subwoofer and built it into the area beneath the driver's seat. I used 0.75 
inch MHD composite with fiberfill and  a metal grill covering the speaker 
cone. This uses the full volume of the underseat area including the storage 
or battery box area. The gap between the top of the speaker grill and the 
base of the seat is about 0.25 inches. The bass fills the entire van, but 
when driving adds to that seat-of-the-pants thrill giver by rapid progress in 
mountain pass shaloms. The subwoofer is rated for  more than 250 watts RMS 
and I drive it with a bridged Profile 300 watt RMS amp. The amp is mounted 
behind the drivers seat against the sink cabinet.

For good results, the system driving the speakers is critical, and I have 
just finished my latest redesign. For powering the eight speakers, a I chose 
a Boss REV-855 4 channel amp. The specs are superb (around 125 watts RMS per 
channel, can handle 2 ohm load, less than 0.01% THD at rated power). The amp 
just fits in the area under the passenger seat. Here, I removed the thin 
front panel blocking access (front of seat pedestal) added a hinged door to 
slide the amp in from the glovebox side. The amp just clears the battery 
box/storage area. I then placed a fitted (read cutoff) rubber battery case in 
this area to safeguard the amp from my tool supply that is kept here. I also 
added two small 12 VDC muffin fans  to the inside volume for air circulation 
and amp cooling. 

For the head unit, I just replaced the previous system with a Sony XR-C9100 
cassette deck and Changer control. This deck has 3 sets of 4 volt RCA 
pre-outs (front, rear and subwoofer) providing full control of input power 
and enabling control of sub cutoff frequency. To this, using Sony's Unibus 
link approach, I have added two 10 disk CD changers, one XA-3B source 
selector (added multiple unilink sources) and an XDP-U50D digital signal 
processor. The DSP is mounted above the glovebox, while one CD changer is 
mounted right behind the drivers seat for easy access by the kids for 
cartridge changing. The second CD changer and the source selector are mounted 
in the sink cabinet. The changer is fixed against the wall facing the rear of 
the drivers seat. The head unit then controls all sources (AM/FM/cassette and 
CD). I also have a Minidisk player that will mount into the system on the 
side of the commode cabinet. The TV unit will have to wait. The DSP permits 
more control of the sound stage that I have with my home system. All filters 
and passband tuning have been done with my Mac Powerbook and an external 
mike. 

The results are quite pleasant. Moving quickly through LA freeway traffic to 
the magnificent sounds of the Ride of the Valkyries (traffic stalled and me 
in the carpool lane) shows a significant sound pressure leak. As near as I 
can tell, the audio level outside the Vanagon is at least 2 or 3 dB lower 
than the inside. F�r Elise can bring tears to the eye (and numbness to one's 
oral response to the booted Philistine demanding some official document). 
Experiences, experiences. 

For more reflective periods, I have installed several headphone jacks around 
the interior (upper and lower births and the dash) for listening while others 
snooze. These are wired through isolators to the speaker outputs of the head 
unit. A relay lets me choose whether or not to power the amps. Finally, the 
IR remote controls all from the beds.

I have taken digital pictures of the stereo install and forwarded them to Tom 
for posting on his site, but I think taking care of the list has consumed all 
his free time. The file is 3.5 Megs without harsh compression and could be 
emailed or FTP'd to those interested.

Hope this leads to enjoyment on the part of some. BTW, haven't heard the 
engine or wind noise for months. Getting harder to hear anything actually.