Trattofon!

Presenting the Trattofon ("funnel-o-phone"). Put this in the mouthpiece receiver of your instrument, and insert your phone to boost the speaker.

Compatible with phones with a width between 40mm and 85mm.

Based on an idea from Seesspinners on Thingiverse: https://www.thingiverse.com/thing:2469784, but redesigned from scratch to accept more phone sizes and have a smoother transition into the mouthpiece backbore, hopefully improving acoustics.

I have so far made a model for trumpet, but the design is (mostly) parametric and has variables for easily modifying it for other brass instruments. Let me know if you want me to upload any instrument in particular.

One caveat is that the text on the front isn't parametric, so it needs some manual work to recenter it and project it onto the surface of the model. I used a combination of the Manipulator Workbench and “Projection on surface” from the Part Workbench to achieve this.

Printing:
I printed this standing up with the part that goes into the mouthpiece receiver upwards and with a brim. Not sure how infill affects acoustics, but from what I know about ordinary mouthpieces, more mass decreases the energy loss between the mouthpiece and instrument, so I would suspect 100% infill is best. I printed mine that way. (Pro-tip for users of Prusa Slicer: Using the “Combine infill every <n> layers” option greatly helps reduce the printing time at high infills.)