I won't get into the technical aspects of coherence or why one speaker is better suited to nearfield listening than any other(mainly because I can't). But strictly from a listening standpoint you can tell when the different drivers of a given speaker come together as one complete whole, and that is what I meant in my post by coherence. In a speaker not well suited to nearfield listening(I agree with Subaruguru about B&W in this respect) with vocals in particular you can actually hear the midrange playing the midrange and the tweeter playing the highs rather than them coming together into one "coherent" or seamless sonic picture. This is why larger speakers where drivers can be spaced well apart from one another may not be good nearfield speakers--the drivers don't have sufficient distance to mesh before the sound reaches your ears. So, in short, despite the benefits of nearfield listening, if your speakers are not well-suited to this type of positioning you'll end up doing more harm than good with a nearfield setup. If you identify the speakers you're using someone here can probably tell you if it's worthwhile exploring this option.
Tim
