Volume level on soundbar is lower than tv

[Mountgr0ve]

I have a Sony bravia TV KD-49XF8796 which has 10 Watt speakers. I find the sound volume adequate at around a setting of 15.

However when I purchased a Sony HT-SF200 soundbar to connect via HDMI arc cable , the sound is inaudible at this setting. I have to almost double it to about 27 or even higher for movies to get more nuanced sounds. I find I'm often increasing the volume to as high as 40. I purchased both about 4 weeks ago. I tried changing the hdmi cable , switching to digital optical cable and Bluetooth. None of which has made any difference. Does the soundbar which is rated at 80watts need to "learn" the volume control ? I assumed if it was 80watt as opposed to 10watt it would be the other way around and the sound level on the sound bar would sound louder when the volume level was the same value. I'm confused as other than the volume setting being so much lower it does sound fine when it is increased to about 40. Which is still less than half the maximum.

[Mountgr0ve]

Further to my original post, I have since realised that in terms of decibels an 80w speaker is not 8 x louder than 10w speaker. Even so I find it strange that I have to have the 80w soundbar set to 40% of maximum for cinema viewing as opposed to say 25% of the 10w TV speakers.(To get the similar volume albeit the quality is superior on soundbar).

If I am purchasing HDMI cable to use with ARC do I need to specify they are CEC enabled or is this standard?