Phone stand folded speaker horn

This passive speaker phone stand really amplifies the sound quite significantly. Even without the insert. High frequencies more so than low frequencies. I tried to increase the surface area of the horn exponentially to get the most amplifiction. But my modelling skills (and math) let me down a bit. But I am still quite satisfied with the result for a first attempt.

Any tips on how to improve the design are much welcome!

The model fits my mi-A1 with phone case: thing:3044340

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