Cathedral Ceiling the Culprit in New Music Room?

Here is me issue. New place - new music room. Dimensions: 22 X 15 with a “cathedral” ceiling running the long way beginning at 8’ and rising to 11.5 feet at the apex. A 4X6” beam running widthwise every four feet.
I am forced to place speakers on one of the long walls. The front wall has two small windows w/horizontal shades at a height above the speakers and components. The rear wall has 15 feet of sliding glass doors and a glass panel which are covered by floor-length drapes. Left side wall is without windows. The right side wall is also without windows but has a 4’ x 7’ opening which enters into a 4’W X 13’L X 8’H hallway, terminating in a door.

I have some book and record shelving along both side walls. I have DIY Jon Risch-design, w/plastic film, 4’ X 16” bass traps in each of four corners (with the rear/right trap in the opening where a corner would otherwise be). Speakers are 60” out from the front wall and 78” out from the side walls. Listening position is centered between the speakers and against the back wall.

With the same components in my previous house (room 19X17) I had very lively, very coherent, very expansive sound. In this room the sound seems rather “dead” by comparison with thumpy and diffuse bass response, bordering and straying into boomy. I am assuming this is mostly due to the ceiling type and I am hoping that this makes sense and that someone has suggestions regarding this issue. I understand that it is hard to make constructive comments without “being there”, but I am even at a loss as to what to try for starters….
I had a room in my house that I used for two years with a cathedral ceiling, just slightly larger dimensions (26x15x 8->11h).
Just for the fun of it I moved my gear into another room here that is almost exactly the same size, but with fewer windows and a normal flat ceiling.
I would never go back to the cathedral ceiling.
No other room in my house sounds like that one with the cathedral ceiling.. I personally do not like it.

I doubt it's your ceiling. It's the open passageway and the glass door. My living/listening room is similar in description, (except with with more openings and no glass door), and the cathedral ceiling is the only thing that keeps it from being a totally hostile area for music reproduction.

The passageway is a big bass trap. The glass doors will cause bass problems in a big way. And on top of that the 15' width of the room will cause low mid-bass standing waves.
All of the glass on the doors is covered with drapery, but I suppose the sound can penetrate them somewhat easily. I have thought of buying an "accordion-type" of divider which I can pull shut to eliminate the passageway. Not much I can do about the 15' width, though. :-( I was hoping to put the speakers on the short wall, but it just ain't gonna happen.
You describe the room as being "dead" and the previous room as "lively". I think with the shelves containing books leaving uneven surfaces to defract sound along with the beams in the ceiling creating sound traps. I think you need more reflective surfaces to "liven-up" the room. try adding a few mirrors and open the drapes. You may have to many sound absorbing surfaces. But I would place your bass traps at the end of the hallway or open that door to prevent or reduce the return of the sound waves once they reach the end of the hallway.
I have a cathedral ceiling. It's a big no-no for stereos, because of the relection back at the stereo. A good heavy rug will help, as well as padded couches etc. for more absorbtion. I think you are confusing people by saying you prefererred the old "lively" room. Your problem with the bass is cause for more bass traps and absorbtive furniture. A "lively" room is usually achieved by more reflective surfaces, giving more high frequencies. In you case I think the problem is too little absorbtion, causing standing waves that are eliminating frequencies. Certain materials, like your glass slider, are highly reflective at high frequencies but absorb low frequencies. If a big panel vibrates with the music, it is turning sound pressure into movement, so it absorbs that frequency.

A few tests: Clap your hands together HARD. You will probably hear a quick succession of diminishing echoes. That's a flutter echo, and needs absorbtion. Bass reflection can actually cause diminished bass, because if any reflection is exactly out of phase with the original, you will hear nothing.

You need expert advise. Send a detailed drawing of the room to echobusters, and they can tune the room for you.