Must speakers have certain volume to sound convincing ?

Well, Getz's sax and even more Gilberto's voice don't impress me regardless of speakers.
Everyone hears differently or processes what is heard differently? Assuming good hearing, of course.

Hello Roxy54, 
You clearly  appreciate both panel and horn speakers.  Which would you choose to build a system around if you could only have one?
Charles, 

I suspect it has a lot to do with how much damage your ears have sustained. 

I think any speaker has to play loud enough to:
1) sound convincing or somewhat realistic
2) portray dynamics
3) pressurize the room
4) reveal, or at least, plumb the lower regions convincingly
5) reveal ambience
One can always go louder but I find that proper matching (or just serendipity) can negate the need to go really loud and still be convincing.

All the best,
Nonoise

Inna,

Too bad you are not impressed with Getz and Gilberto.   Everyone has their preferences.  I happen to like the music, the playing, and the singing, but that was not remotely the point of my post.

The music/playing/singing is a matter of taste.  The SQ on the both the SACD and the Analogue Productions 45 rpm LP is not.  (The former was playing when I heard the SoundLab system that so impressed me.  I own the latter). By virtually anyone's standards (assuming good hearing), it's a very good recording.  By most people's standards, it's better than that.  When you've heard the recording on a well set-up SoundLabs system and still find the recording unconvincing, let me know.

Til then,  I'll file your comment under "not my taste in music" rather than as any kind of informed judgement on panel speakers.