Gramophone to amplify a smart phone

Every morning that I am at the Museum, I walk past a lovely old gramophone. One morning it occurred to me what a beautifully simply way it was of amplifying the relatively quiet sound of a needle on a record. No power is required, simply a trumpet shape. Later, I was listening to music directly from my phone when the thought struck me that gramophone horns could also amplify the sound coming out of the small speaker in my phone. I started making models, and realised, it really worked!