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- My first try
The trunk of my F-Body convertible is very small. Being a convertible, the car lacks the large hatch area of a hard top car. Wanting both a useable trunk as well as the sub woofer required something of a compromise as shown below.
In my first attempt at this I had used a very small amplifier with much smaller wiring. In this case I was using a 500 Wrms amplifier whose manual suggests using 4 gauge power wiring. I needed to upgrade the amplifier wiring. I bought a standard amp install kit that comes with wire, terminals and a Stinger fuse housing. One issue that was important for me was the ability to remove the sub unit quickly without needing tools. I decided to connectorize the amplifier unit. The most challenging part of this is to make up a connector for the 4 gauge power leads going to the amplifier. There is no nice easily obtained connector for this purpose that I could find. I also wanted to make sure that anybody could reconnect it without being able to do something scary like connect the power directly to ground so I made sure that the connectors were unique and could not be hooked up wrong.
I already had a large quantity of GM style weather pack connectors that I got at http://www.waytekwire.com/ (click on Products, then Multi-Pin Connectors, then Packard Weather Pack). These connector's pins are rated for up to 12 gauge wire only. I decided to connect 4 12 gauge wires to each 4 gauge. People get really gung-ho about amp wiring being huge and 4 12 gauge wires are not equal to the total cross section of the 4 gauge wire. The real issue however is the total voltage drop from the battery to the amplifier. Fuses have far less cross section than the wire they supply but they are also just a small percentage of the total length and therefore contribute only a small voltage loss. There is a total of less than 1 foot of the total length where the power is carried by the 12 gauge wires.
Making a decent splice was quite difficult and not pretty. No soldering iron was up to this so it took some effort. I started by stripping the wires back. Then spread out the 4 gauge strands and insert the 12 gauge wires. Then bale it with some copper wire.
A propane torch was needed to heat up the wire. The joint soaked up a lot of solder and required a lot of heat, enough to discolour the wire insulation near the joint.
Here is the finished joint. I later wrapped it up with red electrical tape.
At the battery end, I crimped on the provided terminal. Other than the wire, I find these amp kits quality to be rather poor. No matter how hard I crimped the terminal (I used a vice) the wire would slip in the crimp if I pulled more than about 20 pounds. I took a small 3 mm Allen key and placed it across the crimp and crushed it once more in the vice. You can see the indentation in the photo. After crimping this extra feature, the wire was finally held fast.
Here is the fuse assembly. Although Stinger is a popular brand name, I did not like the clamping mechanism provided. If the wire strands are inserted loose only the middle ones are actually compressed. About 40% of the strands are left loose. If you over tighten the set screw in the clamp, some the compressed strands are actually cut. I decided to "tin" the wire end using the torch. With the end of the wire filled with solder, the clamping is much better, like clamping a solid rod.
The enclosure is modeled on the original but with more enclosure volume and a recess for the amplifier.
Here the lower walls are all in place and the joints are glued and screwed together. I caulked all joints with the same glue to make a good seal.
View inside with brace in place. Its tough to assemble something with MDF without getting some splitting occurring. All the screw holes were pilot drilled to prevent splitting but it still happens in some places.
Upper lid ready to go on.
Enclosure finished with stuffing in place to reduce any boominess.
Top surface upholstered. I use 3M spray adhesive to attach the fabric. The adhesive seems to remain tacky forever so make sure you only spray it where fabric is going to go. The fabric can be obtained at PartsExpress. This fabric is intended for this sort of thing so it stretches pretty well and conforms to a lot of shapes without needing many cuts and folds.
Here is the finished enclosure with the amp installed. The total enclosure volume is about .63 ft^3.
Unit mounted in trunk. The harness connections are visible. It takes just about 30 seconds to unplug the connectors, pull the RCA connectors and remove everything from the trunk.
Close up of the connectors. Its not easy to see here but the power comes through the quad connector on the right. The ground has 3 of the four wires going through a triple Weather Pack connector while the 4th wire goes through a double connector (just behind the triple) along with the amp remote turn on wire. The total is a double triple and quadruple connector that prevents you from hooking anything up wrong.
Although its been referred to as the battle-axe approach, I can get decent bass with the roof down and even with junk piled on top of the sub in the trunk. No, you won't blow anyone away with the roof down, the bass is pretty strong in the cabin with the roof up.