Not sure how to describe this, other than it was a lot of work that I enjoy doing.
I wanted some bass in a Fiero, and found this to be a fairly daunting task due to the lack of space, and the location of the engine, right where the speakers are supposed to go. lol.
I stared at the spaces for quite a while, working things out, measuring this and that, looking at the structure and wondering about whether the sound would travel where I wanted it to. I took a cheap 10, a small "test amp", and some wood and made a "test box for the front. The front was easiest, and had the greatest possibility of success, so I started there. The little box sounded pretty good, so I knew a box would be going up front. I grabbed a 12 that was lying around, and started about finding the mounting location up front. After trying this angle and that, I decided the best place, was to get it as close to the bulkhead as I could, dead center, and vertical. The A/C didnt work, so taking it out gave me just the room I needed. I knew right away that I was going to make the box of fiberglass, but wasnt sure at the time what the structure of it would be. I thought at the time, that the rear box would be glass too, if I could get it to work at all.
I went to the back of the car to look around, popped the trunk, and the prospects didn't look good in the least. This one had me scratching my head for quite a while. I put together another test box for the 10 to see if I could hear anything at all in the cabin. I got a little, but was very skeptical. Then I thought that it might be possible to port the box into the cabin around the engine.
...another couple days of staring at this, measuring that and wondering if it would work at all. I still wasnt sure if a 12 would go in there, and if so, how. I was starting to think that fiberglass wasnt the best option for a rear sub, because the shape of the trunk area would make future removal, or simply changing out a blown sub, impossible. After getting the 12 I had in hand and positioning it here and there, I figured that the only place it really could go, was horizontally, at the midpoint in the trunk. I was suprised to find that I could get 2 of them side by side in there, but it would be really close if it worked at all, I mean really, really close. I took some cardboard, and started making cutouts to establish the final shape of the first pane, the speaker mounting face, the most critical piece upon which all other construction would be built. Once complete, I made the transfer to some scrap plywood I had lying around and sure enough, it wouldnt fit. What to do... Cut the thing in half! It almost went in there then. After some careful thought and trimming, it finally did settle into place. I figured the only way to work with this area and 2 12" subs, was to make a bandpass box. Each of the 4 chambers looked to be just about the right size for a 12, so that much was made to order.
I hooked up the 12 on that sheet and turned it on to see what I had going and got enough sound to go further in the experiment.
One thing I noticed right away, was that there were large gaps under the speaker face board and the trunk body. I thought about several ways to create a seal here, great stuff, fiberglass resin, caulk, I didnt know. I finally settled on this roofing tar like asphalt stuff in a tube from Home Depot. flexible, fills gaps, temperature resistant, waterproof. Yep, that should work. The box would be attatched to the car with about 8 or 10 nuts and bolts fron the speaker mounting panel to the body.
I built the box first, as a prototype out of scrap plywood to see if it could be done at all, and to do preliminary sound checks and determine if I should put any money into the thing, as I really dont have any. A lot of cardboard templates, cutting and filing into place, and I had a full up prototype. I used 2 10s for the initial testing, because I didnt have a pair of 12s. Got a pretty good result, so I grabbed an HE2 Rockford out of the camaro for some further testing. Now this was more like it! I had enough sound to justify further development.
I knew right off that I was going to lose a lot of efficiency from the trunk to the cabin, so I needed some really good subs. I would up settling on some Rockford Fosgate P-2s. Got them for about 100 each online.
I was concerned about the length of the ports, (around 2 feet), creating some sort of an echo effect with the bass, so I set up a test box and the full length of 3" rubber hose I had, about 12 feet. It did in fact echo, sounded really odd. I thought that might kill the project right there, so I had to find a solution. I was also concerned about the small diameter of the pipe, and while working out the solutions I solved both. Polyfill. People put polyfill inside sub boxes because somehow it increases the box volume. Dont ask me how, its over my head, but it works. I needed to make my tube bigger, and eliminate the echo, so I took a couple loose balls of polifill, and stuffed them down the pipe. Presto! Better bass, no echo! Onward.
Now for the porting... This was a hard one. How to get the sound from one place to another, sound isnt really portable. I got hold of some 2" silicone hose, attached it to the top of the box, ran the hose around to the door, and stuck it in the partially rolled down window. That didn't do squat. I tried a bigger hose, a 5" from the portable air conditioner and got a little better result. Ok, but how to get it through the engine bay into the cabin? One thing was obvious, a 5" hose wasnt going to fit anywhere under that hood. I grabbed a pop can, figured that was a decent diameter, and started going from the speaker box towards the firewall to see if I could fit a pop can sized pipe anywhere from here to there. after trying several routes, I decided on running them nearly along the top of the engine to directly behind the seats in the center. The air intake was in the way, so I set that aside and figured I would think up some other way to get air to the engine.
Ok, so they fit, sorta, so how to get it done? I found some 3" black hose, about 12 feet of it, so I knew thats what I had to work with. I wish it was smooth inside instead of ribbed, if I can upgrade to a smooth bore hose I will. I had a 3" exhaust coupler that the rubber hose fit snugly into. This was encouraging, I can;t weld rubber, this made an ideal junction between the car, and the hose!. I was concerned about structure, as I noticed the support beam in front of the trunk was being used to mount the engine, and that beam was right about where I needed the ports to go. Screw it, I could just make a hole right through that support, slide the exhaust coupler through the hole, and weld the beam to the exhaust piece. It worked beautifully by the way, leak proof, and plenty strong. What to do about the firewall side of the pipe? Well, first off, I had to attach the hose to the firewall behind the seats somehow. I figured I would need to weld a washer of some sort to the exhaust coupler, and then I could bolt the washer/coupler thing to the firewall. Simple. Except that I didnt have a 4 or 5 inch diameter washer, and they are a little hard to come by. I decided to use one of the gears from a 10 speed bike instead. Worked like a charm, just welded it up, and the teeth made nice little alignment notches for the bolts used to hold it down. All thats left to do, is trim out the hole so it looked decent, and run the hose.I used a 6" speaker grille to cover the subwoofer port behind the seat. If I dont like the sound, I'll just put a 6 behind each seat through the firewall. Won't be too much trouble to make a little enclosure for them.
I ran the hose from point A to point B, and it cleared everything pretty well. I did add a heat shield to the section that we4nt a little close to the exhaust header by the battery. The air intake was a problem however. I had added a radiator fan to the drivers side leaf catcher, and with the drivers side speaker port running through there, the air intake wasnt going to fit in the stock location at all. A freind suggested that I cut the air intake just outside the round part, flip it over, weld it back together, and pick up the air from over by the battery. It was a good idea, so thats what I did. I also had to cut a nice chunk out of the bottom of the round part of the air filter near the dogbone so that there was enough room for the passenger side subwoofer port.
Now that I knew the rear box would work, I decided to tear it down, get some proper materials, and get to making a box.
I wanted them to look nice and be durable, considering that I was going to be using the box lid as a shelf while working on the engine, so I decided to finish it off with Herculiner. I would up making a fiberglass cover for the front trunk area to clean it up. I left a hole with a plug to refill the washer fluid in the front cover. I used 3/4" treated ply for the rear cover for strength. Don't use anything but Herculiner brand, the other stuff isnt as durable, , and it looks like crap.
There will be 3 amps mounted behind the seats under the ports. One 4 channel for the interior speakers. 5 1/4" alpines in dash, 6" JL audio in the doors, and 4x6 infinities in the rear. One 2 channel amp bridged for the front 12, a Kenwood excelon, and finally, a 2 channel amp for the pair of P-2s in the rear.
Time for pictures!
[This message has been edited by Stainless1911 (edited 09-14-2012).]
If you get one of those 12s and an amp from the department store, it's not going to go well. Since the sub is in the front trunk past the firewall, you want something that can push a little harder than you would get otherwise, but it works very well. I'm running an older Rockford Fosgate HE-2 dual voice coil right now. I wish my amp was a little better, but it's not bad. It's a dual 4 ohm sub. My amp isn't stable at 2 ohms bridged, so I just ran it as a 2 channel, the left to one coil, the right to the other.
Google must've had it cached. Do you still have them? I'm looking at sub options for my '87.
