Even on 8cm speakers you typically have a -3dB point between 100 and 150Hz. For the tiny speakers in notebooks and smartphones it should be even higher. That me

Even on 8cm speakers you typically have a -3dB point between 100 and 150Hz. For the tiny speakers in notebooks and smartphones it should be even higher. That means they maybe could reproduce 100Hz, but at an extremely low volume. And 50Hz is well out of scope.