I am constructing a room of dimension 14D x 19W x 10H for stereo listening am I going correct as per the ratio? or should I change the dimensions I plan to use the long wall Placement for my speakers and diffuse the rear wall of my sitting couch. pl help.
I suggest setting up the other way, with the room longer front to back rather than wider side to side. That way you won't have a wall so close behind you, which also gives better bass response. Diffusion on that wall will help, but it helps even more if the wall is farther away.
I'm with Ethan on this one. I had a 13 x 21 x 8.5 room and originally setup on the long wall. Sound was good, but the listening position was right up against the wall. Setting up on the short wall did force the speakers closer together, but the overall presentation was much better with more stable bass response and more stable soundstage. Sure, the soundstage effect wasn't as wide, but it was much more realistic overall. This arrangement also allowed me to get the speakers farther out into the room.
Current room is smaller (12 x 19 x 8.5) and I have the speakers on the short wall. The room is well treated with bass traps in the corners and behind the listening position as well as absorption at the first reflection points and front wall. Sound is excellent.
As an aside, I don't know if diffusion is the proper treatment for the area behind your listening position as you need some distance between your ears and the diffuser for the effect to work. Absorption would likely be a better choice.
I am constructing a room of dimension 14D x 19W x 10H for stereo listening am I going correct as per the ratio? or should I change the dimensions I plan to use the long wall Placement for my speakers and diffuse the rear wall of my sitting couch. pl help.
In my opinion it will depend on the the type of speakers you have. When I had MBL 111f's they sounded much better on the long wall as compared to the short and my dimensions are similar to what you propose. Some speakers work nicely with near-field listening.
Near-field listening may not correct the room modes Ethan is trying to split by getting 19' further away from 2 x 10'. A close rear wall can impact more than bass depedning upon how reflective it is and what the frequencies are relative to room size and treatments, listener position, and speaker postion.
There are all sorts of rules of thumb and even more esoteric calculations, but setting room dimensions in prime ratios is not a bad place to start...
Prime ratio guy here as well. I have no problems with long wall placement for as long as the loudspeakers are designed with wide and even off axis response. At 14D you can easily get a 8 or even 9 ft triangle. That is squarely midfield. Pluses are the distance ratios from speakers to rear and side walls, added length of travel of reflections from the side walls. The minus is the reflection from the rear wall, which can be treated in such a way that it traps not just the first but second reflections as well. Either way, I'd still treat the ceiling.