Removing switching artifacts from a commercial audio amplifier
Although the speaker ought to be pretty high impedance at the Class E switching frequency, the current will be low, so it should not be causing any faults.

But if you wanted to attenuate the PWM carrier for some unknown reason, you could add a suitable impedance notch filter at the carrier switching frequency.

The output could be shunted by an LC filter.  I believe the circuit is similar to the one in the box.