Bespoke OEM Audio
Overview
My BMW 135i project car doesn't have any options for mounting custom speakers. So, I spent winter break 3D scanning my car, ripping it apart, surface modeling speaker mounts, with the goal to look as original to the car as possible.
Top Skills Utilized
SOLIDWORKS
Surface Modeling
3D Scanning
3D Printing
Wiring
Problem to Solve
A 3-way component speaker set includes tweeters, responsible for high frequencies, mids, for medium, and midbass, for lower frequencies. My car has the base soundsystem, which includes mids in the doors, "subwoofers" underneath the seats, and no tweeters.
BMW does sell tweeter housings, but they only accept fairly small tweeters and are not on-axis with the listeners ears. So, I designed and 3D printed custom tweeter, mid, and midbass housings that accept any standard size of upgraded speaker and that clip and screw into OEM positions.
Scanning
I used the Heges app on my iPhone to use the front LiDAR sensors. Scanned at 0.5mm precision.
Modeling Tweeter Housings
The car comes with blank inserts where the tweeters would otherwise be. I also 3D scanned them, then projected the contours to build curves in SOLIDWORKS, piercing them to form a surface. Trimming then thickening to build solid. This took some time because there was curvature in all axes.
Modeling Mid Housings
The mids by default are mounted in the doors. This works most of the time because lower frequencies don't fall off as easily as high ones when off-axis, but since I had the opportunity to design custom mounts, I created a housing that clips onto the dash vent.
Alternative Mid Housings
I also modeled alternative mid housings for the factory door location. Basic flange but to accept standard mid speakers with a larger basket.
Modeling Midbass Housings
The OEM "subwoofer" location is underneath the seats, which is a speaker clipped into a plastic ported housing. I wanted to re-use this housing, so I designed the mounts to snap into the same location with no fasteners necessary.
Assembly
3D printed everything in PETG-CF to avoid melting in high temps. Also gives a uniform surface finish with near invisible layer lines.
Basically the entire car had to come apart to run the speaker wiring to the DSP and amps in the trunk.
Midbass
Wiring & Amp Mounting
To power everything, I had to mock out a lot of locations to mount an amp. I ended up with a compact Audison Forza DSP and a JL JD500/1 monoblock amp for the subwoofer.
The DSP went next to the iDrive computer and the JL went in a cavity under the passenger rear wheel well in the trunk.
I mounted the fuses and distribution blocks on an acrylic plate mounted to factory emergency toolkit standoffs.
DSP Tuning
Used REW and a miniDSP UMIK-1 to calibrate the speakers to a pretty neutral harman curve, time aligned to the driver.
Conclusion
Car sounds way better and it's just so cool you can scan something with your phone and build something out of it. Still need to do some more DSP tuning, but that's fun.
I will soon post all files to Printables so people can print their own housings for free.
Thank you for reading.
