(Experiment) What if I run a DC motor with unfiltered sine pulse DC voltage?
The main effects of running a brushed DC motor on unfiltered DC are increased loss and heating due to the higher ratio of rms to average current, and increased noise and vibration caused by the motor changing speed in time with the rectified waveform.
This will reduce efficiency and may reduce longevity, but probably not enough to worry about in most applications. It is often done in mains powered appliances such as hair dryers and heat guns, which use PMDC motors powered via a bridge rectifier.