So I finally addressed the lack of bass in my D2. When I bought my truck, it had an Alpine aftermarket head unit in it feeding the factory amp. It sounded awful. I replaced the drivers in the door with Pioneer units and swapped out the rear subs with a pair of Kicker 6 inch subs which I stuck in the factory housing after a few modifications. I installed an amp to power the subs. It sounded OK, but it was never what I had hoped for. Then the sub amp stopped working, which as it turns out seemed to be from the internal low pass filter going bad. I replaced the Alpine unit with a Pioneer unit that has bluetooth that I bought for $75 as an open box deal. I bypassed the factory amp and used the head unit to power the door speakers and swapped out the sub amp for a massive vintage Blaupunkt 5 channel amp (I'm only using 1 channel) that I had laying around and installed the subs in a sealed enclosure. They are 2 ohm subs wired in series for a 4 ohm load. The enclosure uses up the space on the rear door face and mounts using the same threaded inserts as the OEM one. It is about 3 1/2 inches thick. The sub magnets just clear the back of the box. I cut down the factory box so that I could use the OEM grille. I sprayed it with Rustoleum bedliner which looks pretty much identical to the factory plastic. I used the factory harness and soldered wires to two leads on the plug and sealed the plug into the back of the box. I am using one pair of the factory wires to connect the subs to the amp. This setup hits pretty good. If I was starting from scratch, one 8 inch sub would probably be a better choice but since I had the 6's already that's what I used. The box clears the rear seats, although it obviously does intrude more than the stock enclosure.

 

Pretty Nice.

I'm going thru a sound mod on the LR as well, but with everything else going on, it is taking me FOREVER.

I was going to try to put a 8" on the rear door, but with the back seats down it only gave me 5" from the frame of the door to extend out. Add that to the 2.5" inside the door shell, I only had 7.5" to play with, or about 6" inside box to inside box. now figure I would have to cut most of the metal out of a area in the panel of the door, and not wanting to mess with the door latch or handle, I was down to only about 3 different 8" woofers that could be in a box with that little volume. Couldn't find any good 8" candidates that would run well free air.

After a lot of box modeling, I decided to go with 2 Tang Band 6x9 and run them in a infinite baffle design. So now I am replacing the entire box with a "front box" mount for the 2 Tang Bands and just going to deaden the door and handle the acoustic reflection directly behind these.

Once I get that stupid box finished, I will be running them off a Kenwood 4x120 amp that I will bridge to 3 channels. 1 will send 200+ watts to the Tang Bands and then the other two to the front 6.5s in the bottom of the front door. I am replacing those with some Peerless 6.5s.

I'm going to remove the factory amp with a JBL MS8 since the old amp has preset crossover built into it, so I can adjust what frequencies go where. The JBL will also power the existing front mid and highs as well as the backdoor speakers.

Going to top all that off with a Grom bluetooth unit that will connect to the existing CD Changer connection.

I'll try to snag some pics of the process thus far tomorrow.

 

You are working on a whole other level from me. I considered trying to increase the box volume by extending it into the door but nixed it to save time. My work and combination of orphaned and inexpensive pieces has resulted in a pretty decent sounding system while yours will likely sound phenomenal. Please do post up some pictures of the process!

 

Haven't gotten to far due to work, but here you go as promised.

here is making the outside template for the Tang Band 6x9s to sit into

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Routing out the template
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How the 6x9 sits
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make recess for 6x9 to sit flush.
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Baltic Birch front face plate almost finished
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Both Tang Bands mounted on the front plate
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Going to use these as the speaker grill mounts
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Recessing the mounts into front plate
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Extra welding points I a going to weld to the inside of the rear door where the old sub box was. Wasn't too hard to tap

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Need to make the next pictures MUCH smaller.

The idea is there will be a back plate that will use the existing Subs 8mm mounting bolts and the 4 extra heavy duty bolts and mount the entire box to the rear barn door.

I am going to fiberglass the rear and front plates together and let it breath into the rear door like a infinite baffle design. The front of the box will only stick out about 3.5" since the magnets will recess into the door.