I wanted a subwoofer in my '94 regular cab truck, but I wasn't willing to move my seat to accommodate it - it had to accommodate me. So I took measurements and made cardboard templates until I had a good mock up. I bought the biggest sub that would fit my dimensions and then waited for it to arrive before finalizing my design, double checking fit every step of the way. I wanted to fit the amplifier and a hydraulic jack too, so I bought those and worked around the design until everything fit. The finished product is in the pic.

The subwoofer is an 8 inch dual 2 ohm. The box is 14 inches tall, 4.25 inches wide at the top, 6.5 inches wide at the bottom, and is about 1/3 of a cubic foot. Glued and screwed 3/4 MDF. The front angle is about 17 degrees. It has a double baffle, which is why the subwoofer looks sunk in. The box is secured to the truck with three gasketed sheet metal screws through the bottom, spaced evenly and with blue Locktite. Self stick foam insulates the bottom from noise, the carpet panel insulates the rear. My seat position is two notches from the farthest rearward setting, and you can see from the little protectors on the front the bench seat back barely touches. The amplifier is 425 watts RMS. The 4 gauge power cable runs below the HVAC box, behind the passenger kick panel, and under the door sill. The 4 gauge ground is bolted to the floor and a short premade battery cable on the other side of it connects to the frame. RCA and turn-on cables run under the vinyl floor on the passenger's side of the tunnel. It's painted with a grey house paint that I had and thought was close enough to the interior grey. The end grain of the MDF was sealed with an aerosol stain urethane. The other four speakers are aftermarket but not amplified. The head unit is a simple Kenwood unit. The amp and sub were calculated to work with the power the aftermarket head unit had - there is a bit of math to it. It took six weeks start to finish working on it part time.

I've been daily driving this setup for almost six months now with no problems of it or the jack coming loose and making noise. You might think the speaker being so close to the seat back muffles or attenuates the sound; it does not. I get clear, punchy bass. You might worry that a single 8 isn't enough; it is. The cab is filled with accurate, mirror shaking bumps. It makes this old, rough riding work truck a luxurious rust bucket. So bougie.

If you're inspired to make your own, you could easily fit two subs if you don't want a floor jack like I did. If you want bigger subs or need the seat farther back, they do make "shallow mount" subs. The trick was to mount the sub as low as possible and build up air space above it, but the sub I chose didn't need that much air space. The little protectors on the front of the box are what make this work. They protect the speaker from rubbing the seat and give the sound waves plenty of room to propagate (Google "down-firing sub"). Aim for at least one inch of space. One thing to watch out for is stuff can slip through the seat and hit the speaker - get a grill if you can. Be aware - it was a PITA to do so much measuring, fitting, and planning since the space was so tight. But, after living with it, I can't imagine driving without it.

 

Boy, that sure turned out nice, I designed and build a behind the seats dual 8" sub for my Corvette convertible, so I know what's involved in doing something like this, a lot of cutting and fitting, and good wood working skills, not that easy to do. Keep up the good work !

 

Good job. Your box looks great.

Yes 8's get underestimated, but they are a great way to get a lot from little space. This was a fiberglass enclosure I made for 2 8's.