View Full Version : Help building custom enclosure for BMW E90 (09 335i sedan)

03-12-2013, 04:38 PM
Hey everyone,

First post but I have been on the forums here reading up and after long hours of researching, I settled for 2 ID10V3 (2 Ohm) powered by an SAZ-1200D and LC2i as my LOC. I have plenty of room to upgrade to IDQ12's later but I believe I will be very happy with this. I want to keep it as clean as possible and will be building the sealed enclosure with a beauty panel and the subs firing towards the trunk. this is exactly how I want mine to look including the slot for the amp under. What I am having issues with is the actual box dimensions for a sealed enclosure. Looking for .7 cu ft of airspace. The subs have a mounting depth of 5.5" so from I have read, I should add 2" to that for depth. W=35", H=14.25", D= 7.75". Does this sound about right. Does not include division for chambers and will be using 3/4" MDF. Can the box be deeper or will it affect SQ?

Thanks for everyone's input

---------- Post added at 03:38 PM ---------- Previous post was at 03:37 PM ----------

BMW 3 Series E90 E92 Sub Box w Amp Area Coupe or Sedan | eBay (http://www.ebay.com/itm/BMW-3-Series-E90-E92-SUB-BOX-w-Amp-Area-COUPE-OR-SEDAN-/380283968284?pt=US_Speaker_Sub_Enclosures&hash=item588ab0db1c) this is what I'm trying to replicate

03-12-2013, 05:10 PM
You do realize that you will be basically trapping all the soundwaves in the trunk right looks pretty but function is a big loss.

03-12-2013, 05:15 PM
How so? I know people who owns bmws without fold down seats actually drill a large hole into the rear deck to help move some of the sound into the cabin. I'm open to your opinion so if you can elaborate, it would be very helpful. Not looking for a right or wrong, just trying to do this right the first time.

Bumpin Jetta
03-12-2013, 05:15 PM
with your measurements you have about .77 cu. ft. per sub before any displacement. these subs should do pretty well in a small enclosure. i have heard great things about them ported too. great SQ. the box does not HAVE to be deeper. the more airspace you give the subs, the flatter the response. im sure one of the pros on the forum will chime in. adding in some polyfill into the enclosure will help out.

Bumpin Jetta
03-12-2013, 05:17 PM
i agree with dbeez about placement. maybe downfiring box not sealing off the trunk?

03-12-2013, 05:23 PM
I thought i would be since I would be using the rest of the trunk for air space. Not trying to get loud but just have a nice tight SQ hit. ^_^

03-12-2013, 05:47 PM

I'm not necessarily sealing of the trunk but just trying to give it a nicer appearance

03-14-2013, 02:09 PM
Finally got the box panels cut yesterday except the front and will be starting to put it together tonight. Any tips on making the front beauty panel? I figure cardboard but wondering if anyone has the another option

Nut Hair Trick
03-14-2013, 02:27 PM
If cardboard to make a template to trace down on another material, yes. If cardboard as a beauty panel, no. You can measure the straight lines of the would be beauty panel, tape more cardboard to it, cut it to confine to the curves and so on. If you screw up the curves, just tape more cardboard to it and try again. Transfer it over to the harder material. Something like peg board material without the holes should work fine. Either that or 1/2 inch or 1/4 inch plywood.

03-14-2013, 03:01 PM
Finally got the box panels cut yesterday except the front and will be starting to put it together tonight. Any tips on making the front beauty panel? I figure cardboard but wondering if anyone has the another option

Be sure that your beauty panel is far enough towards the front of the vehicle that you can see up to the rear deck from inside the trunk. As far as beauty panels go use the tip above about drawing lines on cardboard. A good trick is to cut the cardboard close to the contour, then take a marker and large washer and run the washer along the contour while drawing the new line on the cardboard, this will translate the exact contour onto the cardboard. When cutting the contour be sure to take your time, and I would even go as far as sanding after cutting so that the curve is perfectly smoothe with completely tangent curves.

03-14-2013, 03:49 PM
Dam you guys are awesome! That washer trick is a great idea! And I don't want to seal off the subs so maybe beauty panel wasn't the right word. The front of the box (where subs will mount) will not only seal the box but fill the contour of the back of the trunk so it's a clean appearance. It will be made out You guys have been very helpful. Ill post pictures once complete. Now as far as mounting and screwing in. I'm thinking 90 degree brackets

03-15-2013, 03:02 PM
90 degree brackets are a good plan, but using this:


will really be the way to go.

Edit: Being as you are in a trunk car, I wouldnt advise these for securing a box in an SUV, as you don't have anything between yourself and the box in the event of an accident.