Does altitude change the sound of speakers??

Boomers.

Google: "speed of sound at sea level vs altitude".
While the speed of sound varies with altitude the reference is to a standard temperature.
Humid air is also less dense therefore lower in pressure and changes
the speed factor accordingly.
For a Pilot operating an Aircraft at 30,000 feet Pressure Altitude becomes a life and death matter but a 5,000 foot difference in a listening room will not change the factor enough to make much difference.
However Caribou Ranch Recordings seem to have some notoriety amongst recording artists.

The speed of sound is irrelevant if it’s the same everywhere in the room. Having “temperature gradients“ in the room would affect the sound, though - E.g., Chinese ice water bowls out in front of speakers.

cm, your ears did not plug up. As the pressure changes you have to equalize the pressure on the other side of the ear drum through your Eustachian tubes. Usually a good yawn will do it. Divers know all about it.
Only the speed of sound changes with altitude. Everything else stays relatively the same. In other words there is no difference from a sonic perspective. 

@marklevinson. Don't know, but that's one of the best moves I can think of. I'm envious. Be sure to explore all that beautiful area has to offer!