Why does the bottom of the Polk MagniFi Mini feel warm to the touch?

The MagniFi Mini is a network active device that includes Google Cast / Google Home. It is constantly searching your Wi-Fi network to remain connected, or to find out if you're trying to stream music or other audio. For that reason, some of the electronics in the sound bar remain active even when it enters "sleep" mode, letting you easily stream music over Wi-Fi when you want to. Note that the warmth you feel will not damage the speaker in any way and passes all Safety and Regulatory requirments.