Best Place to Put a Speaker
Unless you happen to be an architect, there is pretty much nothing you can do to change the shape and size of your room, but there are a couple of things you can do to help get the best acoustics without rebuilding your house.
First of all you need to find out how the room handles sound waves. If it echoes, it could be down to a number of reflective surfaces and objects, such as concrete floors or lots of windows. The opposite of course is dead space, where you may have carpet and a lot of soft furnishings absorbing the sound.