I know that there are already a few active threads about custom sub enclosures/systems on the forum - and I'll bow down to these Fit owners for their creativity and top-notch engineering. Perhaps some will weigh in on my own little idea, though it probably won't be as sexy or groundbreaking.

I've been throwing around the idea of building a small box that would fit underneath one of the rear seats - beneath the "40" seat of the "60/40" split bench - that, depending on some of the surfaces, would either be able to house an 8" or 10" sub. Most likely an 8. I think this may have been brought up before, but IIRC it was just in passing and not subject to in-depth discussion.

I just got back from taking a few measurements, and it seems doable. The measurements are approximately 10" tall from floor to bottom of seat, 10" deep from lip of seat to the back wall, and about 19" from the door to the seat split. Taking into consideration that the box is REALLY going to be oddly-shaped, I would estimate that I'd be able to squeeze at least .6 cubic feet under that seat (internal dimensions). There are several subs out there to choose from that would thrive in such a box - Elemental Designs, JL, etc.

My main question would be: would such a location be bad for a sub? People ask all the time where they should position their sub in their car or hatchback, where to aim it, etc. and almost always the experts say that it's a guessing game - very vehicle-specific. There does seem to be a consensus that in a hatchback, you should put the sub in the rear of the car and face it towards the hatch (low-frequency waves bouncing off and towards the driver). In my setup, however, the sub would be in the middle of the car and would face the front of the car. I really wouldn't want to go through all the trouble of building a box and then finding out that the location renders the sound sub-par.

I've had subs/amps in my previous cars and installed all myself, plus I'm always crawling along other car audio forums, so I'm at least familiar with good car audio. I'm wanting to keep this install as out-of-the-way as possible, hence the idea of the rear seat. I wouldn't be able to put that rear seat down, but it's the small part of the rear seat so I don't think that would be a big deal.

I'll apologize for the long post - if you've gotten this far, you certainly deserve a high-five. Any and all advice or comment would be appreciated!

 

So it would seem to me that you would make the function of the rear seat inoperable as far as eliminating the magic movement of it. Right?
Typically, the sub in that location would simulate putting a subwoofer in the middle of the room at home. You would have some cancellation of bass waves somehow, someway. In other words, it wouldn't work as well.
However, it could be fired side to side against a door (vibrations might be a problem as well as firing into a door speaker), or it could be boundary loaded firing up against the bottom of the seat. Allow 2 1/2 inches or more for the best sound. If you fire it forward, it will work, but the output will be reduced some because of cancellation.
Locating the sub in the very back would yield the best results. You have a ton of room back there as well.

 

Im putting mine in the back also with a sealed amp rack.. Im gonna put removeable latches to latch the sub box to the amprack so if I need to put cargo back there I can just remove the subs and still have my mids and highs working..

 

Thanks for the info, radar. I was afraid of that. I'd always had my subs in the trunks of my other cars, but I thought I could get away with something here. Turns out it's not such a great idea!

I've since rethought the situation and will probably just build a small box that will go behind the rear seat. Would probably still stay with the 8" though - maybe even throw two back there. Not too loud, but nice and tight bass response.

 

I put my box across both rear footwells,( thread; "check out this sh*t"), It is an awesome placement for subs, but... I doubt you'll be able to make a box with adequate mounting depth, even for an 8" sub, and still retain use of the seat. As you already mentioned the floor is irregular shape, and when you put a flat piece of 3/4" across the bottom you are left with far less than 10" mounting depth,( if you still want to use your seats). My box is level with the rear floor and I only had about 7" of mounting depth, and I don't come close to being able to use my rear seats.

 

Two 8's would be the way to go. Really tight sound, and the two would equate to one 11.3" dia. subwoofer. Therefore, more cone area than a single 10. Do them vertically, one above the other so they are coupled together for the greatest output. Separating them into the sides of the vehicle will actually have less output than having them right together. For really crazy response, build a ported enclosure.

 

I saw your install earlier in the week - quite nice, man.

You are right about not having a lot of room if you lay down a flat board - but I was thinking about building it to conform to the floor, over all the mounting brackets and conforming to the bottom of the rear seat. It would be quite an adventure - and I don't know if I've got the skills to do it. The materials and equipment, yes - but not the skills.

That's why I'll probably just throw a box in the back. If you think about it, the sub box underneath the seat will render the seat pretty much unusable from a cargo standpoint because you can't fold it down. With a box in the back, you can still fold it down AND unhook the box if need be. I didn't look at it that way before.

 

radar, elaborate a bit more on your advice about the 8s. I've got a few links stored about box-building, but I have not read them yet. How is it that vertically stacked 8s (one on top of the other, right?) would make a difference rather than having them in the same box side by side?

Thanks. This is very informative stuff!

 

Actually it's the same whether they are stacked or horizontal. I was just invisioning a corner enclosure with the woof's stacked. It would be much more difficult as the back of the enclosure would have to be in fiberglass to fit/tailor to the car.
Here's some tutorials to check out regarding enclosures:
JL Audio
JL Audio

 

Good links. I'm also looking at these:

Car Audio Subwoofer Enclosures

The Subwoofer DIY Page