Several years ago a friend gave me a 12" Polk Audio MOMO subwoofer. I really had no use for it at the time but I bagged it and stored it in my garage for a rainy day. Well, when I bout my 2001 Accord, I figured it was at least getting cloudy and pulled the sub off the shelf to see what I could do.

First thing I noticed was that the enclosure wouldn't work in my trunk. There was no way I could fit it in and still have access to the spare tire. So, I measured out a box that would fit up against the rear seat and still allow me to access the spare tire normally.

I ran into another issue there. A large enough enclosure would also block access from the trunk into the cabin. So I drew up an enclosure that would fit behind the passenger-side rear seat with a lower section that spanned the entire trunk. That gave me an internal volume of .91 cuft. It also provided a nice mounting platform for the amp. (Which I bought from a friend for $50)

The whole thing fits nicely against the rear seat, I have plenty of room in the trunk and the access from the cabin to the trunk is nearly unobstructed on the driver's side.

This is the view from the cabin with both rear seats folded down.

 

Here's what it looks like from the trunk:

 

good deal. i agree that a usable trunk is key. link to my build log is in my sig for other amp mounting ideas that don't take up good space. i fit a full-size spare, three amps, and a pair of 12's.

 

Wow! That is an amazing project and build you've got going there. Looks like you're well over $5k in equipment and materials. I'm aiming a little lower on the stereo for my car.

My budget was $500. The sub was free, the amp was $50, (used from a good friend) and I spent $50 on materials for the sub box. (including wood, connectors and carpet) The Pioneer head unit came in at $200, and I spent about $100 on cables and wiring. (here's where you cringe...) Dual front and rear speakers from Autozone- $70. Throw in a couple of 12V power outlets and some panel mount USB ports and I'm just over $500.

Sound is decent but not studio quality. And, since I still can't find a baffle for the coffee-can muffler, it becomes a moot issue at some point.

Still, seeing what you're doing there has but a little burr under my saddle. I can see some serious stereo upgrades in my future. (the far distant future.)

 

the investment is much lower in equipment than time.

i only have $275 in the speakers and subs total. woofers were $35 ea., mids were $30 ea., and tweeters were $25 ea. - Parts Express and Madisound. subs were $120 BNIB on ebay after being stored for 10 years.
amps were purchased over the years (1999 to 2005) and were picked up on sales.
HU is only $250 used.
so my equipment investment (current) is fairly low. as you can see i've tried many things over the past 6 years to get where i'm at now.

time - well, hundreds of hours of my time is "free". i'm well over the 400 hr mark now.

the key is spending time on install. one thing i have learned is that it doesn't take a lot of money, just some dedication and creativity.

two largest factors are absorption and seals. the fiberglass batt in plastic bags is the single best thing anyone can do to a vehicle door. it improves everything. cheap, easy, and stupid effective.
the second is foam weatherstripping - seals and isolation. another key factor that is cheap and easy.