Tweaks when building a listening room?

lots of good advice and ideas.

i would recommend getting some professional advice on the effect of the shape of your ceiling on the sound. not all 'cathedral ceilings' are the same.....the solidity of the structure and the surface materials will have an influence as well as the exact shape. with a 15' width and height it might be a problem in terms of room nodes.

fixing it later will be expensive and a pain.

the room has the potential to sound very good. a purpose built 2-channel listening room is a joy.

Building the room with the ideal dimensions will make the biggest difference. In your case installing a drop ceiling to the right height would be more ideal. Check out this web site http://www.decware.com/paper36.htm for the golden ratios for room dimensions.

My experience with building to Fibonacci (Golden Mean)ratios is very similar to Sarcher above. I ended up at 8ft H x 13ft W x 21ft L. The room response is remarkable.

Now is the time to consider the AC dedicated circuits and conditioning as well. Consider a dedicated circuit to each component and a large iso transformer on a subpanel just outside the room.

See details in my system.