The Maintenance Files

Car Stereo Installation

(Spring/Summer 2007)

Subwoofer Installation

Now I was down to the last bit of installation.  And this was fabrication time.  I had to make 2 sealed enclosures for the 21V2 8" woofers.  Make a big note of the sealed part.  I discussed it with Dominic & another sources - including the forums of course.  Many go for a smuggler's box mount.  Or a trunk mount.  Hmmm.  The trunk mount means the biggest percentage of your bass output is annoying those near your car.  Not inside it but near it or those you drive by.  With a smuggler's box mount, you lose AC & you are limited to the box airspace minus driver volume & it is directed into the passenger footwell.  It might be OK for a small woofer & reasonably low expectations.

That leaves the front footwells & the rear footwell areas.  The front?  No.  Too much of a sacrifice of the front area.  And not enough potential air volume.  So, it was rear.

That meant fabrication.  Dominic from Focal pushed the idea of a fibreglass enclosure.  He was undoubtedly right, but the idea of me working with fibreglass resin around my car gave me the willies.  Sticky, dripping goop all over.  I can see it.  I could put plastic down & mold it on saran the way it is suggested, but I know myself & what a huge mess I would make.  So that was out.

This left a wooden solution.  With a tip of the hat to Rod Birch & his company Car Audio Innovations. I stole their idea.  I give them credit because they show & sell a rear footwell solution that was the basic model for mine.  I have been told that it wasn't their original idea, since it was so commonly done 'back in the day'.  Whatever.

The advantages to this solution were many:  It created a 20 - 25 litre volume that could be divided into 2 volumes.   It could be removed for tunnel (transmission coupler) access.  It could be strong.  Easy to fabricate out of 1/2" MDF.  Easily damped.  If the carpeting was not disturbed, it could be reversible.  It would accommodate 2 x 8" woofers without issue.

The how was more complex.  Take the passenger seat out.  Trust me.  It's much easier that way.  Start with some cardboard & use it for your trial & error phase.  Cut a piece - double thick - to determine your angle & size.  Mine ended up 12" on the long side & 4" on the top, with a 90 degree right angle join.  See below.

Then, you have to trace the outline on each side of the footwell.  (Note the JMlab logo!)  You have to be inventive to trace it but with some thought, I came up with a trace.  Then I cut some more cardboard to full size by just mirroring the traced side.  There was only a slight difference side to side.  Once you are confident with your cardboard version, cut it in wood.

Sorry, I didn't take more pictures of the build process but I was too into it if you know what I mean.  I added a brace/separator in the middle for support & to separate the too air volumes which is ideal.  And I cut some 90 degree right angles to support & attach the top.  In the left hole you can see the block of wood that I epoxied to the floor on both sides..  This gave me something to attach the bottom of the enclosure to & avoided a screw through the floor pan.

I put some B-Quiet Ultimate dampening on the interior of the enclosure & on the floor - as well as the flimsy access cover on the tunnel.  Then I stuffed the whole box with Polyester fill.  A 1 lb bag filled it nicely.

Then the drivers were gasketed & wired & mounted.

Then I put the top on & tried it.  Not bad but it leaked air all around the edges, greatly reducing the bass impact.  So, I tore it all apart again & gasketed it properly using Home Depot window gasket - the kind with the adhesive edge.  I also added a small metal strap to the top to attach to the body under the rear seat cushion.  These 2 holes were my only 'permanent' modifications.  This allowed me to pull the enclosure back, compressing all of the gaskets that I added at the edges.  It worked nicely & the box is pretty 'lossless'.

I will cover it, of course, once I decide on carpet or vinyl.

And how does it sound?  See Tuning.

Btw . . . no, the woofers don't touch the seat when they're at full excursion.  The picture just makes it look that way.