I'm really glad that, in your case, the update to firmware version 1010.5 has been a success and improved the overall sound quality. However, you might want to consider that when a significant number of people are complaining that this hasn't been the case for them—while also sharing the same issues affecting sound definition—there must be a reason behind it.
I believe that most customers who purchase a sound system costing over €1,000 know exactly what they are buying and what they intend to use it for. Obviously, we’re talking about a soundbar designed to perform at its best with audiovisual content, and in no way is it meant to compete with a high-fidelity stereo system. These are completely different worlds with distinct needs and users. In this discussion, I haven’t seen anyone claiming that their music sounds worse after the update, so I don’t quite understand why you're trying to look for an explanation in that direction.
Moreover, most of us who have had issues with this update didn’t manually install it. Instead, one day, after noticing that the soundbar wasn’t performing as well, we started looking for an explanation—only to realize that the firmware had been updated automatically, without any notification or prior consent. Yes, you may say that updates can be disabled, but as you can see in other forums (Reddit, AV Forums, etc.), quite a few people have been affected by this update.
In my opinion, when a lot of people are complaining about something, maybe—just maybe—it’s worth considering that they might have a point. All they want is for the manufacturer, in this case Samsung, to be aware of the issue, investigate it, and try to provide a solution. In this case, it’s clear that the update hasn’t "worked" the same way for all Q990C units. Just as I wouldn’t argue with you if you say your unit sounds better than before, I think you shouldn’t argue with others when they say theirs doesn’t.
Best regards.
