Yamaha CLP 645 - subdued sound

Hi, I just bought Yamaha Clavinova CLP 645 and it sounds horrible, especially the two main piano voices. It sounds like the sound comes from the cupboard. The tones are like closed and me ears are constantly waiting when they start to play normal. But they will not.

I used to play regular acoustic upright piano and the difference is stunning. I didn't expect 1:1 sound of course, but I expect much more from the piano for almost 2000€.

The other voices don't sound so bad, I have to push Brightness to 10 to have adequate sound, but it is far from "great" sound.

I really do not know, if there is any problem. Maybe it should sound like that, but than it should cost less and I do not understand the positive reviews.

Maybe the problem is in piano, but when I play some youtube videos with the sound of this piano through piano speakers it sounds almost the same.

I tried piano before buying in shop, but I didn't notice such bad sound.