Vintage JBL Driver to Horn Bracket
Overview
I am a bit of an audiophile and my dad shares an adjacent hobby of Vintage Speakers. In his quest to create his ideal sound system, he has purchased a vintage JBL driver and a vintage horn to pair with it. The driver and the horn were not originally paired together. The bracket that the JBL driver shipped with has a different porting design philosophy than the shape of his horn. I took it upon myself to design a bracket to bridge these two components cost-effectively while maintaining the two different design philosophies and being strong enough to support both heavy components.
Mechanical Design
To design a bracket that can bridge these two components, I analyzed the two brackets that would've been attached to the driver and the horn. Upon inspection, we can see that one favored a short time between the driver and the horn while having a steep chamfer to transition into the horn. The other being a slow transition from the driver to the horn and having just all parts mate flat onto the bracket.
I opted to go with mainly a slow transition like in the bracket that came with the driver. However, I would maintain the sharp chamfer that appeared in the other bracket to get the best of both worlds. The driver produced that sound that would be fed into the horn, naturally causing me to lean more towards that design. Additionally, my father wanted to have the bracket be relatively long to allow for building below the bracket if he wished to.
To create a complex shape for the bracket that he wanted, we had some options: CNC machining, investment casting, sand casting, and additive manufacturing. CNC machining and additive manufacturing would be the most viable. It would not be possible to do investment casting or sand casting with tools that hobbyists had access to. It would be possible to send out the designed part to a machine shop to produce the part. However, that could be very costly depending on how we designed it. I have a 3D printer at home, so that was naturally a good first step to take.
Material Selection
As I have a 3D printer at home, the materials I have at my disposal vary from PLA, PLA-CF, ABS, ASA, Nylon, PETG, and many more. For the final product, I considered creep, strength, and accessibility. Addressing creep, I looked at materials with a higher glass transition temperature. This left me with ABS, ASA, or PETG. I had ASA at home and an enclosed printer so that was naturally a good choice.
Strength
To ensure that 3D printing would meet our strength needs, I had to verify the load characteristics the bracket would experience. In my case, I wanted to use ASA to create the final part, but I would be using PLA to test. If I did all the load calculations with the material characteristics of PLA, I would know for certain ASA would meet the stress requirements.
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