My spare tire sub audio build.... need some help!
 

I finally had enough of the terrible stock stereo sooo, here we go!

I plan on adding more detail to this but i have a few questions. Basically Im upgrading my head unit to a Pioneer navigation unit with a backup camera. My speakers are upgraded to the Polk db6501s and I plan to add a slimline 10" sub and amp. Ive built a box that fits into the spare tire and if my calculations are correct, I have 1.5 cu.ft and a mounting depth of 3.5". This is where i need help. I calculated the volume of the sub box by filling it with sand and then using a 6x6x6 box to measure the sand. Well, I counted 3 boxes full, so that would be 1.5 cu.ft., right? ive got pics below....

With the top, the box will sit about 5/8" off the foam top. I plan on adding a carpeted false floor using 1/4" birch plywood and 5/8" mdf(for bracing/raising).

Im not exactly sure how i am going to get enough clearance with a sub grill to remain flush with the rest of the floor....but ill figure it out as i go.

im really ot sure about what sub to get, especially if my calculations were correct with the cu.ft.

also, the amp is TBD as to the sub selection and if i decide to upgrade to Polk mm's :yum:

Any advice is appreciated, hopefully this helps someone else out as well, this is my first custom build with the exception of some simple installs.

I Currently have or have on order:
Headunit
Pioneer AVIC-X930BT Pioneer AVIC-X930BT Navigation receiver at Crutchfield.com
Metra Axxess ASWC Universal Steering Wheel Control Interface
Scosche NN04B 2007-Up Nissan Car Stereo Connector
Pioneer CD-IU51V AV iPod/iPhone Cable for Pioneer AV and Navigation models

Front
Polk db6501 (if theyre blown from using my stock hu, then MMs)

Sub
TBD

Amp
TBD

here are some pics

almost forgot....
I got this..... Color CMOS/CCD 420 TV Lines Car Rear View Camera for Nissan Livina - Tmart.com

and was thinking about this amp kit..... Amazon.com: KnuKonceptz Kolossus 4 Gauge OFC Amplifier Installation Kit: Car Electronics

Math check: A 6x6x6 box is 1/4 of a cubic foot not one half.

thanks guard dad!

I thought something didn't make sense. so, i would have about .75 cubic feet.

i just checked the dimensions:

smaller diameter at the bottom 14" x 2.5"h
portion that covers middle of wheel 8.5" x 1.75"h
larger diameter at the top of the box 16" x 2"h

I did a similar sub and used the Pioneer 10" low profile sub which I was just able to squeeze into the enclosure I made.

I didn't use a grill, I just laid the factory hatch floor panel and carpet over the sub and called it a day. Sounds good too! Just don't through bricks or an anvil on the sub and you are good to go.

Double math check! It's 1/8 cubic foot.

wouldnt 6x6x6 = 1/8 cu.ft? i could fit 8 into a 12x12x12 box.....

if so, that would be 0.125x3= 0.375 cu.ft.??

HA! just posted that!

Bigger would be better but the Panasonic speaker works well in small enclosures. I made the enclosure as large as possible and the walls of the enclosure as thin as possible to maximize volume.

Your enclosure looks shallow, how deep is it in the center?

There's about 3.5" deep including the top

OK-

If you go with a grill the speaker height might not be so critical but keeping crud out of the speaker may be an issue.

If you go with a hidden speaker (my choice) then speaker depth and enclosure depth are critical.

To help minimize the finished height of the enclosure I used a router to hollow out (about 3/8") the back side of the enclosure to create clearance for spare tire anchor-screw and I used a power sander to round off any other points of contact on the back side of the enclosure to allow it to nest into the spare tire as deeply as possible. I had just enough useable room in the enclosure to allow me to recess the speaker about a 1/4" into the top deck of the enclosure. When installed the top deck of the enclosure was even with (maybe a tad above) the factory styrofoam sub deck that rests on the spare tire and creates the floor of the hatch. When installed this way the mounting rim of the speaker stood about 1/4" above the top deck of the enclosure, this was not noticeable with the carpet and trims installed. I also used 1/2" MDF to allow me to better fine tune the final height of the enclosure. 1/2" MDF gives you more precise control of the height of the enclosure than the often used 5/8" or 3/4" MDF but using 1/2" MDF means it takes more layers to build the enclosure.

Pioneer, focal, JL, or kicker slim sub would work here.

I would go focal or kicker.

You do this for a living so you would have way more experience than I but I can say that the Pioneer is only 3" deep, costs about $100, works in a compact enclosure and sounds great for a real-world (good bass but no blown out windows) kind of system.

interesting.....

I think i will go with something like you have GuardDad.

As of now, the top piece of the box sticks almost 5/8" above the top part of the styrofoam deck. I dont mind it being alittle above, especially since i plan on raising the floor at least 1/4" when creating the false floor. Im using 5/8" mdf for most of the box including the top piece which will hold the speaker. If i was able to router down a small portion of the top piece to allow the sub to sit a little more flush, I might be able to use a 5/8" mdf ring to create a speaker grill while allowing enough room for the sub to move(displacement?).

Here is a pic of what i plan on doing, kinda but not as elaborate.....

kudos to butdamnbrian!!!! these are from his audio build and it looks fantastic... good thing my carpet will cover this cause its def not going to look as good.