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Date:         Wed, 16 May 2001 14:20:03 EDT
Reply-To:     FrankGRUN@aol.com
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Frank Grunthaner <FrankGRUN@aol.com>
Subject:      My solution to the Bass and Stereo issue
Comments: To: gmr@obpa.usda.gov
Content-Type:  text/plain; charset="ISO-8859-1"

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. Für 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.


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