@b_limo and @hilde45, You will get a null at any frequency resulting from a distance that corresponds to one quarter wavelength from any room boundary. A sound wave reflecting off of a surface will be exactly out of phase with its primary wave at 1/2 wavelength creating a substantial cancellation of that wave. The formula is 281.5/ ft.to back wall = frequency of null. So if your ear is at let's say, 2 ft from the back wall surface, there will be a substantial null at 281.5/2 = 140.75 Hz. With a 6.5 ft ceiling and normal seating height, one would expect a null at 87 Hz and its multiples. With a 14 ft room depth, there will likely be reinforcement of at 40, 80, and 160 Hz, so one might in fact get some significant low frequency reinforcement from the back wall, consistent with b_limo's comment above and your subjective impression of bass frequencies. In your case there could be some fortuitous cancellation of the 87 Hz null by the 80 Hz back wall reinforcement leading to unexpectedly flat low frequency response. This could be one of those rare cases where long wall orientation is better than a short wall orientation.
With respect to imaging, if your ear falls at 2 ft or less from the back wall, that would give you a delay of 4 milliseconds or less, which might be early enough to not be heard by the ear as a separate signal.
All of this gets an order of magnitude easier with REW measurement. Before I started using REW, I had an acute awareness of things not being quite right, but I wasn't able to put my finger on exactly what was causing the problems and figuring out what to do about it. When you are able to get REW up and running, it will be interesting to see how the room actually measures. I expect you will be able to correlate what you hear with what you measure, and it should enable getting whatever speaker you are working with to perform well in your setting.
With respect to imaging, if your ear falls at 2 ft or less from the back wall, that would give you a delay of 4 milliseconds or less, which might be early enough to not be heard by the ear as a separate signal.
All of this gets an order of magnitude easier with REW measurement. Before I started using REW, I had an acute awareness of things not being quite right, but I wasn't able to put my finger on exactly what was causing the problems and figuring out what to do about it. When you are able to get REW up and running, it will be interesting to see how the room actually measures. I expect you will be able to correlate what you hear with what you measure, and it should enable getting whatever speaker you are working with to perform well in your setting.