What is ideal dimension size for a home listening room?


Is it a cozy size, large living room, 10 x 15, 20 x 30, some where in between?  I guess it shouldn’t be square.  Let’s assume ceiling is 7 1/2.  Heard ceiling height means a lot.
emergingsoul
20' x' 24' x 9'.  Textured ceiling, wall to wall carpet, one end opens to a dining room with a vaulted ceiling, lots of upholstered furniture.