BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > AUDIO/VIDEO + BLUETOOTH + Electronics/Alarm/Software > E93 Subwoofer, HiFi

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      09-04-2012, 08:05 PM   #1
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E93 12'' Subwoofer firing through SkiHole, HiFi

Car: 2009 e93, I.Drive, HiFi, No ski-hole pass through from factory.
Speaker: Alpine TypeR 1242d.
AMP: MRP-M500 - connected@4ohms
Box type: Sealed 1.0Cu
Connection type: T.tapped
Tutorial Used: http://www.e90post.com/forums/showthread.php?t=87130. Except the remote is coming from the thin black cable in the back, no need for LVT2 module.

What is a ride to work without being able to feel a good kick drum to start your day or the depth of a bass line when you return from a club or a bar? I really like the 8'' subs the car has under the seats, but there is something missing. I noticed the sound sometimes pretty good or other times, very bad. It all depended what song I was listening to or the format, mp3, pandora, etc.

Very weak bass output + "Ski hole pass through" = Custom speaker box for the Ski hole .

What a brilliant idea, I though I was going to go to ebay and find one instantly, not really. It left me thanking for the years I took woodshop in high school because I was going to have to build one myself, jaja.. Hadn't really seen anyone using a box through the ski hole right to the back of the seat for a convertible. So Im off to the drawing boards. The first mocks where of a ported box but I decided to go sealed, saves me space and more detail. Im not sure, but I think sealed is better with the top down, I sense more pressure in the cabin so it shouldn't be so sensitive to wind as with the ported.

My car originally didnt come with the skihole pass through, but i was able to remove 2 panels that opened it. I can buy later on the 2 pieces needed to make the ski hole pass through look stock. http://parts.bmwofsouthatlanta.com/s...ssembly=259155 .

The custom box:
Everything was made from 3/4'' MDF. The first piece you cut is the bottom piece that looks like a "T" for the floor. Then go on to cut the half octagon. There are 5 pieces, first cut the two walls that consist of 2 pieces. Dont do the top piece, this will come at the last. These pieces you can do one by one and sand them till its right. One thing i noticed is that the measurement you will get from the opening in the back is not the same size as the opening into the cabin, it gets smaller, so dont glue anything just yet and try not to overcut as much as possible. You will build the remaining back side of the box. Then at the end you can cut the top piece while you actually test it in your trunk space to make sure all lines fit flush. You will have to be very precise, because for a 12'' woofer the opening barely makes the top and bottom diameter of the woofer. On the inside of the box, i also had to sand some of the top and bottom walls so that the subwoofer fits nicely. Also note that there is an angle in the back seat, the woofer sits at about a 10 degree angle. I also put an extra 3/4 wall in the back wall of the box since i noticed that this is where most of the speakers pressure was being pointed at.

The Amp connection:
http://www.e90post.com/forums/showthread.php?t=87130. Except the remote is coming from the thin black cable in the back, no need to buy an LVT2 module.

The verdict:
Alot of the mudiness is gone. The bass sound is much cleaner. No more crap sounds when you want to feel your music. Much better quality through all genres and formats. I have the crossover point of the amp at around 95hz, gain at 30%, with the 1242D Alpine. At some levels the bass, in my opinion is too much. There are no major rattling noises inside the car. With decent volume turned up, on the outside, with the doors closed, the bass is hardly noticeable, definitely no license plate rattling. Stock tweeters still sound dull but I think the subwoofer has cut some of its harshness.

This is my first custom box and my first amp install, so im still working on some details like the flush mount for the speaker rim, sealing the trunk and cabin partition. Also trying to maybe add some foam or shock absorber to sit it in the trunk.

Any ideas or suggestion, much appreciated.

Pre-Drill everything.
Lossen up the joints and try to fit in before gluing anything.
Used Titebond glue for joints, do not use liquidnails!.
Crank this box up in your home stereo to test it for leakage and sensitive points.
Using a JL Audio W6, insert some poyfill.

10/15/2012: Installed W6
The difference between the Alpine and the W6 is noticeable from the second you hear it. The Jl carried more notes in a warm smooth tone.

02/2/2013: Updated
Inserted lots of polyfill. Seems to kill the punchiness coming from the eq'd stock amp. Although you can lower the crossover point to avoid this , some notes will not be picked up by the system.

8/3/2013: Installed 600/6 , front components
Im understanding now how bad stock speakers are for your car and ears.

Last edited by 2009-e93; 08-07-2013 at 08:40 PM.
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      11-06-2012, 03:32 AM   #2
Drives: 2007 335i coupe
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Nice... great idea!
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