You know, I've asked myself many times why I even have a coffee table. It's pretty much just a glorified footrest, at least in my place. It's not all that big, but considering that it has nothing on it, it probably hasn't been doing me any favor sound-wise. I guess it's time to get rid of it. Would a bookshelf below a speaker cause issues?
That's pretty much what my coffee table serves as too. I'm assuming that you're talking about having a mounted speaker above a bookshelf. Is that what you meant? If it is, how far does your bookshelf stick out? I'm not sure if it would matter, but you never know!