Four years ago I put together a custom stereo system for my Tesla Model 3. At the time, I designed and 3D-printed speaker mounts that allowed me to install aftermarket speakers in the factory speaker locations. That included putting 6.5in woofers in the front doors. Well, after four years of beautiful sound, a few weeks ago I started hearing distortion in one of the woofers. Unmistakable, extremely pronounced, right around 175hz. After a few weeks of dread and ignoring the problem and skipping past songs that accentuated harmonics of that frequency, I finally took apart the door panel and found that the printed plastic speaker mount was still in one piece but was pretty badly warped. I wasn't at all surprised.
I wonder if there is an eleven-syllable word in German that means "the disgust you feel when you look at your earlier work and see all of its glaring flaws". Looking at my speaker mounts from four years ago ... damn ... so many things done wrong. So many more things not wrong per-se, but limited by my resources of the time.
- The speaker mounts have lots of gaps and weak spots in the plastic, especially missing infill, because I had a very cheap printer at the time that had lots of problems with under-extrusion. I have a much better printer now and I'll be printing with four- or five-layer walls.
- I designed the speaker mounts as if they were being made from sheet metal. Everything was flat plates. I have no idea why I did that. The new parts are made from very simple lofts that provide much more structure.
- The previous parts were waaaaayyy too complex. So many steps and features. And if you change any one, all the subsequent features break and have to be redesigned. The new part consists of seven features that are designed in parallel from a set of initial drawings so any one can be changed without affecting the rest.
- The walls were really thin. I don't know why I made them so thin. Was I trying to use as little filament as possible? Or minimize print time? I don't know. The walls on the new part are much thicker.
- The parts warped because they were too thin and I printed them out of PLA and my car was in Texas. I used PLA because my cheap printer couldn't do ABS and I hadn't yet heard of PETG. The new parts are printed from PETG. And I moved to California.
- The speaker mount that failed was just the most essential geometry, with no gussets for reinforcement. The new mount will be much thicker all around so it doesn't need gussets.
- The flanges between speaker/mount and mount/door were sealed with duct tape. (It's just barely kinda compressible.) I didn't have any compressible foam at the time to seal them properly. I considered using felt this time, but I assembled the new mount and decided the flanges are smooth enough that they don't need to be sealed.
- I printed the old mounts in multiple pieces because my printer at the time couldn't print larger than 200mm. I glued the pieces together using super glue because I didn't know that cyanoacrylate doesn't bond well to PLA, or using gorilla glue because I was just lazy. These days I would use epoxy, but now I can also just print the entire part as one solid piece.
- When I took the old speaker mount out, the screws holding it onto the car door were fairly loose. Those screws insert into plastic blocks the threads in which were probably loosened by my turning the screws in and out dozens of times. I'll probably use loctite blue when reinstalling them.
- I put a cover over the back side of the speaker to prevent water from dripping on top of it. It was glued in place on the back of the speaker mount and it was loose when I removed the mount, about halfway broken off. This might have been the main source of the 175hz noise. My car just spent a month sitting outside in record-breaking rain and the doors were bone-dry inside, so this cover is unnecessary and I won't include it on the new mounts.
- I used spade terminals on the wiring connections originally, but I found them to be loose and slightly corroded. I'll just solder on the wires when I reinstall.
- The wires were routed through a small hole which had to be sealed or potted. The hole was just big enough to allow a plain wire through, so the wire had to be terminated after it was passed through. I replaced that hole with a simple divot on the edge of the mount.
Hopefully these new adapters will last the life of the car. The originals had tons of problems and they lasted four years, so these should last another 6-10.