Soundbar 700 and bass without Bass module

[DepoBose]

Hello everybody, I just bought a soundbar700 and I am really satisfy regarding the surround system and the clear voice but I have a big doubt : The bass, I don't have the bass module and I don't want to spend other 800 euro, when I am listening music from Amazon music or Apple is very rich and the bass are very good but........when I watch a movie or streaming series the bass are very very poor. Why do I have this big difference between music and video bass?

The soundbar is connected to the TV by HDMI eARC. 

Thank you very much and I will appreciate every answer.