How to tell if Acoustic Treatment is Needed?

Stand in the middle of the room and clap your hands a few times and listen for an echo.....if you have one, then some type of treatment is needed.

This of course is just one way....

I have a room very similar in size/volume to yours. Mine is 12X24 with a ceiling sloping from 7 to 11 feet and a more vaulted ceiling at one end away from the system where the room is wider. Speakers are 8 feet from listening position on the long wall. I think it depends largely on the contents of the room and the room materials and construction, so my room may not resemble yours beyond the surface measurements. I definitely require some treatments as my room is very 'live' with lots of hard surfaces. Just putting a few houseplants in the room helped. When I changed from a fabric to a leather couch that made a huge difference in how the room sounded (fabric was better being much more absorptive). Riley's suggestion definitely would have indicated need for treatment in my room which is much improved with the addition of a few panels, plants and curtains. Still, it does need work. I guess my suggestion to you is this:

STOP RIGHT HERE:

I have no complaints; I think the sound is very good although with 60 year-old ears and not a lot of experience with high-end audio systems I don't know whether MY budget system can be better.

It's kind of like going to a group of wine snobs and saying, "I really like this wine - can you tell me why I should not?" There will always be something "better", make no mistake about it. If I did feel the way you do about my room I would probably just enjoy what I had rather than put the effort in. When I've made changes it is because there is something about what I'm hearing that really bugs me and I know I can improve it because I've heard it done. Music is a wonderful thing, and what a privilege it is to have it brought into your home that way.

That said, very easy and basic steps to take that could help a setup like yours (based entirely on my experience): treat the first reflection point (if there is one - this assumes the speakers are at one end of the room). This treatment could be as simple as a large houseplant (diffusion), but is more commonly done by an absorptive panel. Next, by your description your listening position is up against a (back) wall. That wall ideally should have some diffusion panels against it behind your head. You could also try bass traps in the corners of the room behind the speakers (again, this assumes the system is at one end of the room). If the system is centered in a 22 foot room on the long wall you may not have the issues of a first reflection (except on the ceiling) or corners directly behind the speakers (though you may still benefit from bass traps in the room). You are basically listening nearfield and are probably avoiding some of the problems you may have in a larger room.

Good luck, and congratulations on putting together a system you really enjoy.

What Jax said! If the system/room interface provides you with what sounds like real/satisfying music to YOUR ears; COUNT YOUR BLESSINGS!!