I bought a Samsung Soundbar Model HW-Q70R/ZA. My TV is a Samsung UN46D7000. I connected the soundbar per the manual. Optical cable from TV to Soundbar. HDMI output from soundbar to HDMI ARC input on TV. Soundbar displays TV ARC. I checked and AUTO PWR is ON. The volume automatically turns itself down. I have the volume set to 30 and within a few minutes, it resets to 23. The TV sound options are set to SPDIF Output. The sound drops out occasionally also. Pretty frustrating to have to up the volume every few minutes.
Re install the firmware on the sound bar here is a video provided by Samsung on how to reset/update your firmware.