Here are a couple of shots of the iPhone speakers I have so far.
First shot is both sides of an iPhone 4. the outer two contacts I measured as 23.5 ohm and the inner pair as 8 ohm.
Could there be two 'coils' inside? One appertaining to the Loudspeaker effect and the other to the earpiece effect. Don't know yet but obviously the earpiece effect won't be required.
Second 2 pics is the iPhone 6S Plus, described as the Loudspeaker.
The two contacts measures 8 ohms. The sound port is on the end and very small. Just inside it has a material gauze, I guess to stop dust.
I am still awaiting delivery of the iPhone 6 speaker and the I will test them against a Sugar cube.
Hope this helps.
Dave