So I’ve been messing around with a few phones lately, a nexus 6p, a pixel 3a xl, and a s21 ultra, and I’ve noticed that on the 6p and 3a xl both sound louder, punchier, and clearer when compared to the s21 ultra. They also both have that thicc notch design with a massive speakerphone which might add to the high volume levels.
Speaker technology (at least for something “old school” like stereo) hasn’t improved significantly for a very long time. That’s not to say it’s not good, we just figured out how to make a good speaker a long time ago.
DSP has improved since then but no amount of DSP will make regular speakers sound like great ones (like the nexus 6’s) of the same size or type