2005 Civic LX 4dr
How would I install a sub without taking up any precious trunk space?

I can't get rid of the spare donut. What if I put the donut some where else? But where?
Or what if I cut a hole at the bottom/floor of the trunk?
I'll probably have to stick with something on the small side like a 10 inch or an 8 inch.

 

How about an 8" free air sub mounted to the bottom to the rear deck?
OR maybe a console type box that fits between the back seat floorboards?
I think an 8 or a 10 with a good amp will provide plenty of bass, especially ifits mounted inside the cabin...

 

What's a rear deck?

 

where your rearspeakers are mounted. behind the backseat headrests. at the bottom of the rear glass.

 

the spare tire well has some extra space between the spare and the back of the trunk. that should be enough room for a sealed inclosure with one, or maybe two 8's. i built an open top tool box for this space in my coupe and it's no trouble to get the spare out past it.

 

Its ok to cut the metal?