What kinds of shortcomings are we talking about? In simple terms, we would say that the XS Book exhibits a series of small, subtractive distortions. Subtractive distortions are those that involve the speaker not doing something desirable (or at least not doing it as fully as one might wish). Often you don’t notice these sorts of subtractive errors nearly as much as you would additive distortions. Additive distortions are more in your face, and thus more noticeable and distracting (a good example would be the upper midrange glare we’ve encountered so often with other small desktop speakers).
Let me provide a few practical examples to illustrate ways in which the XS Book transcends subtractive distortion.
The XS Book doesn’t deliver much bass below 50 Hz, which you might think would be a serious omission, but in practice it is not. You sense a certain lack of very low-frequency information in the overall balance of the speakers, but you have to think about it a bit because the speaker doesn’t thrust this problem at you. On the contrary, the bass that is present mostly sounds right, while the missing low bass frequencies rarely seem conspicuous (although we think some listeners might think about adding a subwoofer to complement the XS Book’s low-end output).