I understand how a potentiometer works on a an average medium speaker for a pc or Bluetooth. The power needed would be low enough so that a potentiometer can take some power by increasing its resistance in series with the speaker( I know that overall power is reduced as well.)

Still my question is for small devices that has no potentiometer like a phone. So do they use a MOSFET and control its resistance with the voltage applied with a DAC (internal or external to the main processor)?

Or is it possible and doable to control speaker power with PWM at a frequency much higher than sound frequency range 20hz to 20khz ?

I am mainly asking of what is possible and really about any idea u have on mind.

And for power devices that control large speakers. Well definitely no potentiometer is controlling a 2000w speaker volume directly. Is it multiple heasink-cooled MOSFETs or PWM maybe?