Does My Dad Need A New Phone?

So my dad has the Samsung S8+ phone. I have the Pixel 4. In his car, he bought a bluetooth receiver which works fine. When I play my audio from my Pixel 4 phone, the bass and sound is loud and clear. It is loud to the point where I have to lower the volume on my phone or car speaker system. However, when my dad connects to the bluetooth receiver to play his audio, the sound is low and he has to have his phone volume on maximum volume and have the car speakers at maximum volume also to get decent sound. Why is that? Is it because my dad's phone is a few years old (April 2017)? If I connect my phone to bluetooth and if I have my phone volume and the car volume both on maximum volume it is super loud sound. I'm not sure why my dad's Samsung Galaxy S8+ plus phone has a low sound when playing through bluetooth. Can you guys help me out here?