[jrrtt09]

I haven't seen this sort of subwoofer installation on a gen 8 yet, if you aren't familiar with infinite baffle in a car application, the idea is to use the cabin of the vehicle as the subwoofer enclosure. In my case, I'm sort of using the trunk as an enclosure that leaks to outside of the car, so technically it's an aperoidic enclosure. I'll get to that later, first I'd like to thank SCompRacer for sharing their install with the LC7i, that gave me a head start with my wiring.
I chose the Blaupunkt EP1700X for my LOC, which is similar to the LC2i but was $35 at the time of purchase. I cut the rear speaker wiring between the front and rear doors (Gn/GnBk & Wh/BuBk) and ran new wire from the rear output of the factory head unit to the EP1700X. I cut both pairs of wiring from the front speakers in the kick panels (Bu/BuBn & Ye/YeBk) and ran new wire from the head unit side of the Bu/BuBn to the left rear speaker (Gn/GnBk). I did the same for the Right side with the Ye/YeBk and Wh/BuBk wires, this connects the front output of the head unit to the rear door speakers, so all of the factory door chimes will now play through the rear and will not have any additional amplification.
I'm using a new set of components for the front doors with a 4 channel amplifier, so I ran 2 new sets of speaker wire from the trunk to the kick panels where the Bu/BuBn & Ye/YeBk wires were cut. The tweeters were connected directly channels 1 and 2 on the amp, and the woofers were connected to the supplied crossover which was connected to channels 3 and 4 on the amp.

The amplifier is an Andeman AS-5040, I have nothing great or terrible to say about it, but it was only $37 and is louder than the head unit, the HPF goes from 120hz to 3khz, I'm running the woofers at 120hz HPF (with the 3khz passive LPF) and the tweeters at 3khz HPF. I'm also using a 400uF capacitor on the rear doors to create a 6db 100hz roll off. Door speakers are Hanma Q6500 and Q6501, I couldn't find much information on them at the time of purchase, but I suspect they're a copy of another brand. I paid $40 for the components and $27 for the coaxials, I can't give an honest opinion at the moment due to too much rattling in the doors (I'll be adding butyl deadener and neoprene foam).

 

[jrrtt09]

I already had a Soundstorm EV2500M amplifier for the subwoofers, it'll push around 600W RMS before clipping, though I'm running at 4 ohms so I'm probably close to 500W running at the highest LPF setting, which is 90hz. I came across the DS18 Gen-X 154D subwoofers and thought the specifications looked like a good match for my plans, I paid $156 for the pair and another $30 for wiring for both amplifiers. I'm running 4ga power from the rear battery to the subwoofer amp, the 8ga from the subwoofer amp to the 4 channel amp. Remote turn on and RCAs come from the EP1700X. I wanted to keep as much trunk space as possible and still allow my rear seats to fold down and be able to carry 8ft lumber in the car.

I drew everything up in CAD and came up with a design that maximized trunk height at the center but still allowed a deep mounting depth for the subwoofers.

Lower portion of the baffle complete

Foam was used to template for the top portion of the baffle, also used to template and cut some of the sheet metal from the rear deck

Top portion cut and attached

Subwoofers mounted

Side panels added for rigidity, it just barely slides into place from the trunk opening

Temporary rear deck cover added

At this point, it's installed but not completely sealed from the cabin. I plan on adding another layer of wood on top of the rear deck to sandwich the sheet metal between 2 layers of foam and 2 layers of wood. I'll also tidy up the wiring and permanently mount the amps and LOC at that point.

 

[jrrtt09]

Here are some photos showing the extent that the rear deck needed to be cut. The On-Star module has be be moved, which means the trunk light has to be disconnected.

 

[jrrtt09]

A quick update, I initially ran the 15s through the subwoofer output of the EP1700X, but that output has a high pass filter at 33hz which I don't want or need (it also has a 1khz low pass filter), so swapped it to the main output. With that I lost the bass correction but gained the low frequencies, it seems like Chevy lowered volume below a certain frequency, but still allows frequencies to play down to 10hz. I plan on installing midranges in the A pillars and crossing over below 1khz, at that point I'll run the door mid-bass speakers off of the subwoofer channel of the EP1700X and tune the bass correction from there. One other issue I have at the moment is a turn on pop, I'll try to fix that next week with a 400uf capacitor and 5kohm resistor.
Overall, I'm very happy with the IB subwoofer setup, it plays the 17hz tone in "bass I love you" better than the Fi Q 18 I had before (it doesn't do much with the 7hz tone), and plays up to 80hz well enough for my liking. It plays the lows like a home theater setup, but plays fast and clean like my old 4x10 bass guitar setup. I've been running them at 4ohm (around 300W) and they'll adjust my rear view mirror at 35hz. I'll try it at 1ohm (around 600W) to see what they can do, but will probably go back to 4ohm.

 

[DrivenDaily]

You should also try "Flight of the Cosmic Hippo" by Bela Fleck and the Flecktones. I can make my house shake, and in my car my mirror droops like you describe.

 

[jrrtt09]

Well the Soundstorm amp lasted about 10 minutes at 1 ohm before going into protect mode, so I disconnected a coil on each to bring it up to 2 ohm. I downloaded Flight of the Cosmic Hippo and that bass line definitely goes to the mid 30s. Not quite the 31hz low B from a 5 string, but lower than the standard drop D tuning on a 4 string. Thanks for that suggestion, I'll keep it on one of my playlists.