To clarify: You can see the high-frequency switching signal at the amp's output, as @pma demonstrates above, but the IMD generated by the tweeter itself would have to be measured at the output of the tweeter to see if it is audible. I have no idea if that actually happens in the real world, or if the tweeter (or its crossover) effectively blocks such signals. The tweeter may just refuse to move and turn the HF energy into heat, or its inductance could block it but cause voltage ripple through the crossover, etc. I can think of several ways such HF signal could, or could not, cause problems, but not something I have ever measured. That said, @pma's measurement shows there is current flow into the speaker, so that energy is going someplace.