[sor]

Hi guys. It seems like a new car always creates a whole list of projects.

I usually like to beef up the bass a bit in factory systems. I don't go all out with competition-level ported subs and thousands of watts of power in order to play pointless trunk rattling tracks, but just a little something to give a bit of that concert-level tactile bass.

I hate having a sub box in the back to deal with, so I wanted to find a way to hide it and keep things as clean as possible. With the X3, I decided to take advantage of the compartment under the floor of the cargo area. There isn't much space under there, but enough to fit about a 1 cubic foot enclosure, and with some carefully selected speakers that should be plenty.

Unfortunately, I didn't really see an obvious space for an amplifier to go, so I figured I'd need to design an enclosure that could accommodate space for an amplifier to be installed in the same area.

I began by measuring the dimensions of the space, then by looking around for subwoofers. Most manufacturers these days sell slim subwoofers that work quite well, and I've used a few over the years. Once I found a model with the right combination of size, power handling, and a reasonable required enclosure size, I found an amp and noted its dimensions so I could design a spot for it.

There are two common ways to make custom oddly-shaped enclosures. 1) use fiber glass and resin, or 2) use the stack-fab method to cut layers of MDF and assemble like a layer cake.

Fiber glass is difficult to do right, is messy, and is smelly for weeks. I'm OK at basic 3D modeling, so I drew up a box and sent it to a local wood routing shop to be cut out. Then I clamped and glued, and sealed the inside with poly. So far things are going quite well, the box is assembled and fits, cargo floor closes. I do plan on carpeting the box to reduce vibration.

Waiting on carpet, speakers, and amp to arrive.

[arciga18]

SOR,

I can't keep up with your mods.


I like this. Unfortunately I got the Spare tire.

[sor]

Well, all the more room, just need to jettison the spare!

[strike4A]

Looks very pro. What about cable routing and did you already discount upgrading the existing underseat subs?

[sor]

I’ve done factory sub upgrades before with mediocre results.

They’re usually an odd size, for one. This one, based on the design shown in the parts catalog, looks to have a unique design and mounting system. It isn’t just an 8” hole. I’d need to find something customized to the car (like a bavsound upgrade) or come up with a sub and enclosure that would fit in the tiny space.



You can possibly find something with better sensitivity, or something custom fit for the car, but in my experience it generally doesn’t have the power behind it that I’m looking for without also upgrading the signal.

I don’t really want to start cutting stock wires, oem brackets, and ripping out seats just to take advantage of the space where the current speakers are. The effort to use this area in the cargo floor is pretty low and I’ve got access to both power and speaker signal to tap into.

Im waiting for a few pieces before wiring things. I’d like to try to carpet the box first. I bought some individual binding posts and intend to drill two 1/4” holes for them in a convenient location. I think that will be easier to seal than making a 2” hole for a speaker terminal cup.

https://www.amazon.com/gp/aw/d/B0002KR3X0

I didn’t really make any special accommodations in the box design for routing amp cabling or anything. I’m probably just going to wing it and try to keep things as clean as possible.

[Keweenawbee]

Originally Posted by sor

Waiting on carpet, speakers, and amp to arrive.

As Larry David would say-
Pretty, pretty, pretty cool.

[Zeroblade]

This is looking sweet lol. Hope you cover the wood with matching black carpeting

This actually made me wonder if BMW is using the same Harmon kardon speakers found in like a F8x. Would be sweet to get bavsound stage 1 speaker upgrades too

EDIT: Nvm, bavsound already confirmed stage 1 set lol

[bwcooper]

The man has skills.....

[Yizu]

In the Netherlands they sell a custom made system from gladen. Really perfect sound but very expensive.

Cost incl. build-in is €2500.

[Max Well]

Very clean and precise work, sor - will be interested in seeing the final product!

[voyagergab]

I see what you have in mind

[starbai]

seems really slim... what subs are you planning to use?

[sor]

Originally Posted by Zeroblade

This is looking sweet lol. Hope you cover the wood with matching black carpeting

This actually made me wonder if BMW is using the same Harmon kardon speakers found in like a F8x. Would be sweet to get bavsound stage 1 speaker upgrades too

EDIT: Nvm, bavsound already confirmed stage 1 set lol

Not sure about matching, but I did carpet today.

[sor]

Originally Posted by voyagergab

I see what you have in mind

It's looking more like a cassette tape now.

[sor]

Originally Posted by starbai

seems really slim... what subs are you planning to use?

There are a few options. I built it with either of these in mind:

https://alpine-usa.com/product/view/swr-t10

http://www.rockfordfosgate.com/products/details/t1s2-10

I've used the Alpines in the past, had a single 10" direct swap into the rear deck of my Audi S4, and a single 12" box floating in the back of my last car. They're not cheap but they work well and only require .4-.6 cubic foot of enclosure.

[bwcooper]

...a very particular set of skills.......

[sor]

Originally Posted by bwcooper

...a very particular set of skills.......

Not those kind of skills, unfortunately(?).

[voyagergab]

[kozzi]

This thread...



Keep up the good work Sor!

[sor]

Originally Posted by voyagergab

That’s more like it.

[BobsM3Coupe]

From the looks of the woodwork alone, sure looks like you've done this kind of mod before.

Very nice.

[Keweenawbee]

I was looking for joinery and what I got was glued laminations. Has got to be way more solid this way.