Apple has never officially revealed the power of the speakers that the Apple Watch has incorporated and that is why the website of iClarified wants to show the speaker power comparison made with the new Apple Watch Series 6, the Apple Watch Series 5 and the older Apple Watch Series 4.
In this sense we can think that the Series 6 has to be the winner since it is the latest model and possibly the one with the best speaker, but you may be surprised when you see the video They have done by measuring the power in decibels of these three Apple Watch models.
The best thing is that you watch the video directly to clear up doubts:
Yes, the Apple Watch Series 6 is somewhat "less powerful" in terms of sound despite being the newest. We also have to say that this difference is practically null and imperceptible by the human ear so this cannot be used as an excuse at all. That said, the comparison is made without music directly with the pink noise that is much more linear and that is ultimately the one used to perform this type of measurements.
It is also curious that the power in the new watch models is somewhat lower and should have some logical explanation. In any case, it will not be Apple that explains this minimal difference in the power of the speaker of the new Apple Watch Series 6, so we are not going to give more laps about it. It is simply somewhat inferior in sound tests no more.