I have a Samsung HW-R450 soundbar and a 2021 Samsung QLED tv. They are connected using HDMI via the ARC connection. I sometimes find that when playing live tv the volume on the soundbar does not sound all that loud even with the volume set to full. 

Netflix is sometimes the same, however playing 4k discs and blu ray films the sound is louder with still more increase in volume available.

Does anyone know if this is down to the sound being transmitted low or could I have the bar set incorrectly. Anything I should check?

Thanks in advance.