RE: 4kq sub install?

[Michael Hogan <mikhogan@stic.net>]

>Date: Wed, 28 Apr 1999 08:22:01 PDT
>From: "Stacy Mohr" <samsims@hotmail.com>
>Subject: 4kq sub install?
>
>Anyone one have a good solution to install a sub in a 4kq?  Audi was 
>not thinking about stereo gear when they put the gas tank in the 
>trunk.  I just bought a bazooka rs 10 (amplified), installed it, not 
>happy with the results, so its going back.  There is just too much 
>stuff between the listener and the sub, ie gas tank, trunk liner, 
>sheet metal with few holes in it, and a back seat.  The only time i 
>get bass is when the volume is turned way up.  My next thought is to 
>build a custom enclosure that fires a sub (or two) up at the rear 
>shelf, and cut a hole in the rear shelf sheet metal to get more sound 
>into the cabin.  This looks to be a challange.  Any words of wisdom 
>out there?

	Stacy,
		In my Coupe GT (I think trunk and rear deck are nearly 
identical to your 4kq) I built a custom enclosure to house a single
10" Cerwin Vega driver (cast aluminum frame, very efficient SPL,
300w rms, low -3dB cutoff...).  If you are serious about doing this,
then expect to sacrifice about 70% of your useable trunk space.  My
driver in a ported enclosure called for a 1.5 ft^3 volume to tune
to somewhere near 30 Hz.  I started by removing the felt deck cover
to be sure there was enough room for the woofer and the port to fire 
through the baffle and into the interior.  There is, but barely.
Then I constructed, out of cardboard, a three dimensional template
held together with duct tape.  I built the enclosure when the box 
volume was correct, modeled after the template.  Don't neglect the 
volume taken up by the materials themselves - I used 5/8" MDF from 
a local speaker builder.  

	Here is some crude ASCII "art" approximating a side
view (of course the top should be slanted upward a tad) :
		   
			     .....................
			      \	 	    .
				\		    .
				 \		    .
				  \		    .
				  /		    .
				 /		    .
				/		    .
			      /		    .
			     /			    .
			    /			    .
			   /			    .
			  /			    .
			 /			    .
			/			    .
                   ___________________________

The box should ideally wrap around the irregular contours
of the fuel tank.
The base is screwed onto a 1"x8" plank which is screwed
into the two parallel pillars which surround the spare
tire space (yes, the spare still goes in and out).
The woofer and port both are installed on the top.  I cut
holes through the sheet metal using a jigsaw.  The 3" pvc
port sticks into the car about five inches above the deck
liner.  The woofer is covered by a fabric covered grille
made from leftover MDF.  Looks pretty cool, IMHO.  While
you're at it, you would be wise to install better than OEM
rear speakers in the deck (I use 5 1/2" components, no cutting
required).  Oh, yeah, for extra rigidity, screw the sheet
metal deck onto the top of the box.
	I carpeted the box and my amps are screwed on the
back.  I've built several custom boxes in as many cars, and
this one sounds as good as the best of them, with a bonus:
the bass is nice and loud IN the car, but barely noticeable
OUTSIDE the car.  Maybe a negative for some people's tastes, 
but I don't enjoy broadcasting my every bass note to the 
public.
	One possible problem I forsee is that if you have to 
service your gas tank or fuel sender, then it will be a PITA
to take the box out.  If this sounds too daunting, you may
consider just cutting a port through the deck and porting that
Bazooka to it.  It would surely sound better than having it
enclosed in the trunk.
	I _might_ have the plans still laying around, and if
you're interested, I could scan them as well as photos of the
finished product.

HTH
Michael Hogan
87.5 CGT