How do I determine the largest enclosure that can possibly fit into my trunk

[NASTY08IMPALA 5,000+ posts]

Take the dimensions of where the box will sit permanently and then measure the void behind the wheel well against the opposite trunk opening and see if that dimension is larger. If it is, then you can fit the box. If not, consider making the box narrow enough to fit through the trunk width and then make up the difference in depth.
Of course, the latter option will likely interfere with your spare tire access and if so, then consider smaller subs. ;-)

if op is wanting a 18 in his trunk spare tire acess is long out the window..hell i have no acess at all with a pair of 12s

 

[jrdnhsnbrg 10+ year member]

if op is wanting a 18 in his trunk spare tire acess is long out the window..hell i have no acess at all with a pair of 12s

Single 12... No access, but my box is overkill and I love it like a child

 

[bubbagumper6 5,000+ posts]

My box barely fit, it took me, my dad, and my grandpa all pushing on different pieces of carpeting in my trunk to get the box to slide in.

I built a fairly large enclosure once that was so far away from fitting we had to completely scrap it and start over.

My last large one would fit but you had to remove the rear seats and all plastic panels from the B-pillar back in order to get it in (then reinstall in reverse). It did have a minor issue with the slanted back seats and bottom of the enclosure (it was wedge shaped) but we just cut off the point with a circular saw and put a strip of wood in the slot to seal it up. Maybe lost .1 cuft (not enough to affect tuning) and she fits like a glove now, haha.

 

[jrdnhsnbrg 10+ year member]

I built a fairly large enclosure once that was so far away from fitting we had to completely scrap it and start over.
My last large one would fit but you had to remove the rear seats and all plastic panels from the B-pillar back in order to get it in (then reinstall in reverse). It did have a minor issue with the slanted back seats and bottom of the enclosure (it was wedge shaped) but we just cut off the point with a circular saw and put a strip of wood in the slot to seal it up. Maybe lost .1 cuft (not enough to affect tuning) and she fits like a glove now, haha.

Oh, the things we go through to have a subwoofer...

 

[adjetta 10+ year member]

I remember kicking an 8.5 cubic foot box into the the trunk of a 98 jetta, good thing it was 1"mdf, otherwise it wouldn't have made it

 

[adjetta 10+ year member]

okay so i had a piece of peg board and i cut it to be roughly the same size as my box bottom and i slid it into the trunk until it bottomed out and measured from that point to the lowest point of the trunk roof, not sure if thats accurate but maybe it will give me a a good idea

 

[bbeljefe]

if op is wanting a 18 in his trunk spare tire acess is long out the window..hell i have no acess at all with a pair of 12s

Um.... DUH.

I guess I missed the whole part about it being an 18". Thanks for pointing that out.