This acoustic speaker from ReAcoustic for your iPhone utilizes a vintage Attwater gramophone horn from the 1920's and is mounted to a hand crafted wooden base. They require no batteries, cords, electronics or power source. They are completely acoustic! Simply place your iPhone in the slot and enjoy tunes of yesterday or today with an amazing vintage sound. Great conversation piece.
These work on the same principle as a megaphone. With a megaphone, you speak into the small end and it is amplified out through the large end. Ninety years ago this gramophone horn amplified a small driver "speaker" that was below it. Today, this same horn amplifies the small speaker that is built into the iPhone in the same way.
This model only works with iPhones and not with iPods. With the iPods, they either do not have a speaker, or the speaker they do have isn't loud enough to be effectively amplified this way.
To see a demonstration on YouTube of how this speaker works, please see HERE.