Custom trunk subwoofer enclosure build...
 

I've had my 550i for a little over 2 years and decided it was finally time to have some fun.. After reading some of the reviews and recommendations on various forums last December I purchased a set of the Earthquake SWS 8ix shallow mount subs plus an amplifier and had them installed under the front seats.

Before I go any further...

There are a few misconceptions about our sound systems I want to address..
First off if you don't have the Logic7 system in your car like me then you have 2 small "subs" under your seat and a few door speakers. For those of you that think the stock subs don't really do anything you have no idea what you're talking about. If you unplug those subs you'll quickly realize you car sounds like an alarm clock. Almost all of your mid and low signals go directly to these speakers. Just a heads up.. Your tiny under seat subs do a fantastic job all things considered...

Secondly I would like to say that the Earthquake under seat subs do hit quite a bit harder but are VERY EASY to overpower and distort. I purchased a amp to match the specs of the subs (150watt RMS per channel) and I'm only using the amp to about 20% and I'm still pushing the subs to the max..

If I had to do this all over again I'd probably skip the Earthquakes and jump to a 12" sub in the trunk... Because unless you're willing to sink the extra time and MONEY you'll never see the value in the under seat options.

So now that you're up to speed.. Here's what I ended up going with..

I decided to purchase a signal processor to dedicate (bandpass) only the middle frequencies to the under seat subs. And this is where the subs really shine!! They are fantastic mids.. Solid punch, zero distortion, and excellent sound quality overall.

Doing this meant I lost all of my low signal. So I purchased another amp and sub to handle just the lows..

After a day or two of trying to figure out a box to build I decided why not just build the trunk out with a custom enclosure.. So here you go..

This is the design for the enclosure I put together in photoshop to give myself an idea of what I was getting into.
Attachment 154127

Here's the basic box shape
Attachment 154128

Attachment 154129


I'm not quite done.
The only thing holding me back from finishing the box is the sheet of Lexan I ordered to serve as the front of the box (so you can see the sub magnet). Also the amps will no longer be inset because of space issues.

Ordered some really trick wire connectors because you'll see everything with this set up. Should be done by next weekend..

Let me know what you think


More pictures to come as I get closer to completion.

If you are implying that the woofers on the non-Logic7 cars are smaller, that is not true.The Logic 7 & and Hi-Fi systems have the same size woofers under the front seats on US spec cars. See attached BMW training guide on the difference between the two systems.


Do you have the ski pass through?


It looks nice, but I couldn't sacrifice that much usable trunk space.

Ok go back and read that manual closely... Because you're wrong..:oops: The Top Hifi system has bigger subwoofers under the seats. Check page 16 and read the line about central woofers..

How did you miss that?

Anyway I would be worried about trunk space but the truth is it's not a big deal.
I designed the unit to allow the spare tire to still be accessible. Plus the entire unit comes apart easily for complete removal..
Also did I mention this is my weekend car?

Keep reading that manual pimp!

Actually, you're wrong incoherent. Hi-fi system Page 12 "The central
woofers have a diameter of 200 mm and a load bearing capacity of 40 W. The transmitted
frequency is between 30 Hz and 500 Hz." Top Hi-fi system page 16 "The central woofers have a diameter of 200 mm and a load bearing
capacity of 70 W. The transmitted frequency is between 30 Hz and 500 Hz."

Ok guys... You win.. I said bigger when what I should've said was better.. Now that we've gotten the "who gives a shit" portion of this thread out the way.. What say we get back on topic before you number dorks break the internet.. Surely you can't be the only type of people that own these cars..

Anyone here not care about the specs and just want a well tuned bangin system? Stay tuned.. Everyone else can inbox me with their TPS reports.. Don't forget the cover sheet..

incoherent- I think you are on the right track with your observations about the E60 audio system.

How many watts are you planning to run? Also won't your lows be distorted (will not get the full effect of lows) due to the material that separates the trunk from the inside cabin. Unless your seats fold down, but then you lose the capability to have people sitting in the back. Also there will be trunk rattle.

Though your design is nice looking. But if you are going through all of this to achieve the sound. Then this design is flawed.. If I were you, I'd change the design of the box. You can keep it where you can see the sub through the Lexan glass. Just instead of making a standard box like you did. I'd make it similar to a 6th order box, porting it directly into your inside cabin. This will allow you to achieve the sound you are seeking. And there will be no trunk rattle (dynamat is not required for this type of enclosure). And we all know dynamat can be expensive if you need to do your full trunk.

With this design, you can have your trunk open and the sound will never change inside the car. Also since there is no pressure in the trunk for when the sub hits. There's no trunk rattle & standing behind the car, you will barely even hear the sub at all. All your lows will be coming from the side & front of your car.

I'm running 1200 watts total.. 600 to the front subs (earthquake) and 600 dedicated to the 12" sub in the trunk..

Also sound quality is my priority so I'm sticking with a sealed box. However I will be cutting a hole through the back seat behind the center fold down to allow the bass into the cabin..

I'm thinking about picking up some L7 speakers this week to swap out my remaining stock speakers. Anyone have experience with this swap? Worth it?

More pictures to follow this weekend.. Should be all wired up by Sunday night.:thumbsup:

Sounds like a plan. Will you be posting a sound clip as well once you are done?

I'll post whatever you want.. The weekend can't get here quick enough.. I've had the trunk torn apart for about 2 weeks now so I miss driving the car.. I don't get enough days off..