Your Constraint: Easily removable adhesive so as not to strip the paint or stucco. -> This may limit the weight of what you can hang on a wall which is correlated to acoustical thickness, generally speaking. Because the popular fiberglass filled resistive-type absorbers should be a minimum of 4 thick (with 6 being better) and an air space of another 6, the total depth is now quickly approaching what a bookshelf depth would entail. So you might need to place acoustical treatments where you can afford them to stick off the walls which may be your front and back walls, presumably, and use thinner devices for the side walls and ceiling.
Your Need #1: Eliminate slap echo. -> Luckily, slap echo is more of an upper frequency phenomenon usually above 1kHz so it takes thinner treatments to deal with it than lower frequencies. Have someone stand by each speaker clapping their hands while you sit in the listening position to see if you can hear the slap echoes and then try placing a thickly folded or rolled up towel at various positions along the wall and repeat the clap-listen tests until youve found the wall position where the slap echo is minimized. Then replace the towel with something more permanent to break up the hard parallel surfaces. A tapestry or thick drape was suggested and will work well. If you have some art work / pictures on the walls, then try placing a tennis ball between the wall and the bottom of the picture to angle the picture upwards. You might consider the lightweight RPG Skyline diffusers that are 2*2 square which can be hung with Velcro or sticky tape and shouldnt damage your walls/ceiling.
Your Need #2: Improve focus and imaging. Reducing the indirect reflections by eliminating the slap echoes will help drive the ratio of direct-to-indirect reflections higher and help with focus and imaging. So too will listening in a near-field arrangement and toeing in your speakers. Try absorption on the front wall to attenuate the damaging reflections coming from there the absorption should improve the perceived soundstage depth.
Lastly, a little education on room acoustics will go a long way. Try picking up Dr Floyd Tooles latest book and F. Alton Everests textbook and plough your way through them. In the long run itll help you assess your needs, the quality of manufacturers products and help with knowing what to place where.
Good luck.
Your Need #1: Eliminate slap echo. -> Luckily, slap echo is more of an upper frequency phenomenon usually above 1kHz so it takes thinner treatments to deal with it than lower frequencies. Have someone stand by each speaker clapping their hands while you sit in the listening position to see if you can hear the slap echoes and then try placing a thickly folded or rolled up towel at various positions along the wall and repeat the clap-listen tests until youve found the wall position where the slap echo is minimized. Then replace the towel with something more permanent to break up the hard parallel surfaces. A tapestry or thick drape was suggested and will work well. If you have some art work / pictures on the walls, then try placing a tennis ball between the wall and the bottom of the picture to angle the picture upwards. You might consider the lightweight RPG Skyline diffusers that are 2*2 square which can be hung with Velcro or sticky tape and shouldnt damage your walls/ceiling.
Your Need #2: Improve focus and imaging. Reducing the indirect reflections by eliminating the slap echoes will help drive the ratio of direct-to-indirect reflections higher and help with focus and imaging. So too will listening in a near-field arrangement and toeing in your speakers. Try absorption on the front wall to attenuate the damaging reflections coming from there the absorption should improve the perceived soundstage depth.
Lastly, a little education on room acoustics will go a long way. Try picking up Dr Floyd Tooles latest book and F. Alton Everests textbook and plough your way through them. In the long run itll help you assess your needs, the quality of manufacturers products and help with knowing what to place where.
Good luck.