2008 Pontiac Grand Prix GXP - Fi IB3 15"

[peq]

EDIT: See post 7, I got an extra 3 inches

I'm working on putting a 12" Fi IB3 2-ohm sub in the trunk, attached to the back deck, from the bottom. Most call this Infinite baffle or trunk baffle.

I'll power it with an Alpine MRP-M500, which should supply 500 watts, which is right around the 550 watt rating.

I'm running the Alpine MRP-F450 4-channel amp to power the stock speakers that came with the Monsoon system. I'm using the stock wiring that originally ran to the tiny factory amp. I have no idea what the ohm load of the speakers are, so I'm not sure how many watts I'm feeding them. The factory setup was bi-amped for the front doors, so 2 channels of this amp are for the front door tweeters and 2 channels are for the front door 6-1/2s.

The crossover situation has changed 3 times now, hopefully to stay this way for a long time. I started out just using some passive crossovers from an Infinity component set, and eventually purchased a Clarion active 3-way crossover.

The Clarion and 4-channel amp were mounted directly to the metal under the back deck, up-side-down, and it sounded just fine. It came with a knob for subwoofer control and did everything I needed it to.

But.... When I had to disconnect it to do a test fit 6x9 to 12" adapter, I accidentally connected the Clarions ground wire to + on a live battery. I didn't have the ground connected, but since it was mounted to the car's metal, it was grounded already. Smoke started pouring out of all the gaps around the knobs, even though it was mounted up-side down. Needless to say, i toasted it and needed something to replace it, so I ordered up the RF 3Sixty.3.

Since the MRP-F450 has unpainted silver stripes and the M500 doesn't, I decided to paint the MRP-F450 so they would match. (they were purchased several years apart).

I have a JVC headunit that I installed into the bottom cubby. I replaced the stock headunit with a 7" Touchscreen VGA/HDMI LCD screen.

In the trunk I have installed a Zotac Mini-PC with a 1.8Ghz dual core Intel Atom. I'm powering the PC with a car charger advertised as for netbooks.

I've ran 1 vga cable, 4 pairs of RCAs, and 2 Cat5e cables to the trunk.

I bolted a 3/4" piece of MDF to the underside of the back deck. I fastened it with some bolts through mostly factory holes, but I drilled a few along the seams of the steel. I'll fill in all the holes later with some sealant.

I've added a secondary deep cycle battery to the trunk. I picked up a Optima Yellowtop from Autzone on a whim a few months ago. I built a small rack in the corner of the trunk that should let me hide it behind the trunk's side carpet.

I need to buy an isolator so the batteries don't drain each other. I'm still running a traditional battery under the hood for now. I'll probably get another yellow under the hood just so they match.

[P4killer_]

ok??

[Polish]

Cool build man, looking good so far.

[flarobbie]

i just got rid of my gxp... here is a vid of it with 2 lvl5 15's on a mojo 4kw. killin my spoiler!! im still pissed i sold it. imdeff. tuned in to this build since i never got to finish mine.

[peq]

I just got an e-mail with tracking info, and I found out I'll have my new sub by the weekend!

I ordered the Fi IB3 12" 2-ohm on Superbowl Sunday, and it finally left NV today. I read on the Fi forums on their site that the wait time was up to 3 months because they're so busy, so I'm thrilled it shipped in under 2. (They really need to adjust the quoted times on their site, because they're still showing "Estimated build time of 10-15 business days")

Since I thought I was going to be waiting a few more weeks for the proper sub, I decided to cut a ring and mount a temporary woofer (an old Kenwood 12" with unknown specs, definitely not intended for IB use). I haven't even put my back seats back in to hear it properly yet, but now it looks like I'll probably just wait until I get the new one mounted.

I drilled the standard 8 holes for mounting, then I drilled and countersunk 8 more (1 more between each the mounting holes).

I lined up the ring so it would cover the factory hole in the back deck and screwed through the countersunk holes into the wood under the back deck. I ended up lining one of the sub's mounting holes with one of the 1/4" bolts that I mounted the wood with, and then I used wood screws for the rest of the sub's holes.

I have a feeling that the weight of the sub + its vibrations + driving vibrations would work those screws loose very quickly, especially once I swap it for a sub that around twice as heavy. I'm not sure how I'm going to do it yet, but I'm going to use bolts instead in the final install.

I'll probably either weld nuts to the top of the deck, or install t-nuts to the top of the wood so that I can pull the sub as I please from the trunk, without having the pull the cover over the back deck (which required pulling the seats).

I'm also not sure what I'm going to do with the back deck cover. I would like to not have exposed subs or grilles screaming “STEAL ME!” at people through my rear window. It has two factory grills for 6x9s (which are now pulled and plugged), and it has a very thick section in the center which I'm assuming is factory sound dampening.

I'd like to try to cut a hole in it from the bottom of it through everything but the top-most layer of carpet, but I’m not sure how this is going to sound or look .

That's all for now. I expect to be wrapping the trunk up on Sunday. At the very least, I'm going to have the back seats and deck cover installed.

[peq]

I forgot something.

A few weeks ago when Fi called to let me know they were busy and behind, I mentioned that I wished I ordered the 15 instead of the 12. He said he would call me about the difference in price after he talked to someone.

Saturday I got the package from Fi. I opened it and found a big ass sub with no logo on the dustcap and no markings on the woofer that I can see. This is probably because the most common use of the sub is in home theater.

Here she sits next to my old Kenwood 12".

I had the trunk prepped previously for the 12", so I had to rip the old ring out and make a new one.

I was in such a hurry to see how this was going to sound (and look) I didn't take any photos while we were using the jack to lift it into position.

Here's the pic of it installed the first time.

How does it sound? I haven't put my back seat in to find out yet.

I held a thin piece of plywood up to cover most of the hole and got a taste of what it could do, and I think this will sound pretty good once I get the back deck to stop flexing so much. I'm going to drill holes to use bolts that go through the metal for all the sub mounting holes, and add more to the wood, then I'll put the seat in and see how much more sealing I have to do.

I underestimated the size. It would probably take up less room if it were mounted firing behind the seats, I'm thinking about moving it to a piece of wood behind the back seat so that they fire directly into the cabin instead of hitting the back windshield

[flarobbie]

lookin good so far... you gonna put a box around that sub or jut free air it??

[peq]

lookin good so far... you gonna put a box around that sub or jut free air it??

The sub is designed for use without a box, just something to separate the back waves from front waves.

I need to take some pics for an update. Last week I ended up doubling up the wood because it was flexing a bit.

I haven't yet properly sealed off the trunk, but it sounds good as is. It isn't extremely loud, but it goes low. I had to play around a bit with the EQ on it pretty much to make it sound right, so the 3Sixty is proving to be a good investment.