Interesting enough all the comments. Personally I have found that most demonstrations are using servers to access music. I have not found that many that to my ears sounded as good as a good transport and DAC like a CEC, Metronome, Audiomeca transport. I am trying to get there myself but nothing that really does what these transports do. So to me that is one cause of the treble issue.
I recently heard a ProAc monitor and a Vandersteen monitor. At first, the Vandersteen sounded slow and not to involving. The ProAC seemed livelier, faster and more open. The Vandersteen had a more musical sound with better decay of notes and to me hearing piano notes fade away is the correct sound. It was more spacious sounding also. But the jump factor with the ProACs was fun. It was during this comparison that I remember thinking the ProAC tweeter was a little tilted up in the frequency offering the fun factor. Exciting but maybe over time not correct and long term listening could be an issue. I wanted to have both but that was not an option.
Living in the NYC area, I get to hear so many systems. I am able to understand more of what causes the poor sound from these experiences. I find the issue mostly is coming form the source than the speakers. I usually bring a DHT DAC with me so that I can hear what it does in these systems. Usually within the first 30 seconds everyone hears the differences for the better.
So to me it is not as much the speakers or the set-up as it is the source feeding the system the sound most of the time.
Happy Listening.