Mid-sized speakers are usually too small to fit on a bookshelf, but placing them on the floor can cause problems with sound quality. For one thing, the drivers are not at the same height as your ears, which means that your ears are not in the center of the cone of sound produced by typical cone drivers (ribbon tweeters are an entirely different matter). Another problem is that woofer is so close to the ground that almost half of the sound cone is directed into the floor, where it either gets muffled by carpeting or brightened by a non-carpeted surface. This can cause a muddy bass response that lacks the punch and tightness that it should produce.