To add a few ideas to Soix's excellent post -
Doing the top octave (and beyond) well is often pushing the edge of the performance envelope of our systems.
If your source is digital, the DAC you're using makes a helluva difference when it comes the top octaves (and it doesn't have to be a megabuck DAC either). One place where analog really shines is in capturing that sense of air and ease.
Amplification is also important - you need an amp that doesn't clip or compress the leading edge of the transients, yet you also need an amp that decays properly and isn't "spitty". Getting the decay of notes right is more difficult than getting the initial attack right. Poor phase response in an amplifier can cause it to exaggerate the sibilants ("sss" sounds) and become fatiguing, despite having peceptually "extended top end".
In my experience, there are two factors that contribute to a natural sounding top-end in a speaker. The first and most important is the lightness of the diaphragm, as this contributes to its ability to trace every nuance, and respond without rounding off the transients or blurring the decay. Electrostats excel here - the Quads, Acoustats, Martin Logans, InnerSounds, and Sound Labs are all capable of superb top-end resolution (the Sound Labs use the lightest diaphragm I know of). Speakers that use ribbon tweeters also do quite well, but generally have a bit less resolution because the conductor/diaphragm is heavier than the mylar diaphragm of an electrostat. Red Rose, Newform Research, and Magnepan come to mind. Note that proper matching of speaker with amp is essential for each of these designs.
Now the second, and sometimes hidden, factor in a good top end is uniform dispersion. If a speaker beams in the top octave, then the direct sound will have a brighter tonal balance than the reverberant field, and the ear/brain has to work harder to integrate the two. This can cause listening fatigue over time. The Audio Physic speakers use a tweeter that has very good dispersion. Other speakers mentioned here that have exceptionally uniform dispersion include the Sound Labs, Maggies, and Newforms - the Sound Labs by virtue of their large, curved diaphragm which radiates over a constant 90-degree arc front and back, and the two ribbon speakers by virtue of their exceptionally narrow diaphragms.
Doing the top octave (and beyond) well is often pushing the edge of the performance envelope of our systems.
If your source is digital, the DAC you're using makes a helluva difference when it comes the top octaves (and it doesn't have to be a megabuck DAC either). One place where analog really shines is in capturing that sense of air and ease.
Amplification is also important - you need an amp that doesn't clip or compress the leading edge of the transients, yet you also need an amp that decays properly and isn't "spitty". Getting the decay of notes right is more difficult than getting the initial attack right. Poor phase response in an amplifier can cause it to exaggerate the sibilants ("sss" sounds) and become fatiguing, despite having peceptually "extended top end".
In my experience, there are two factors that contribute to a natural sounding top-end in a speaker. The first and most important is the lightness of the diaphragm, as this contributes to its ability to trace every nuance, and respond without rounding off the transients or blurring the decay. Electrostats excel here - the Quads, Acoustats, Martin Logans, InnerSounds, and Sound Labs are all capable of superb top-end resolution (the Sound Labs use the lightest diaphragm I know of). Speakers that use ribbon tweeters also do quite well, but generally have a bit less resolution because the conductor/diaphragm is heavier than the mylar diaphragm of an electrostat. Red Rose, Newform Research, and Magnepan come to mind. Note that proper matching of speaker with amp is essential for each of these designs.
Now the second, and sometimes hidden, factor in a good top end is uniform dispersion. If a speaker beams in the top octave, then the direct sound will have a brighter tonal balance than the reverberant field, and the ear/brain has to work harder to integrate the two. This can cause listening fatigue over time. The Audio Physic speakers use a tweeter that has very good dispersion. Other speakers mentioned here that have exceptionally uniform dispersion include the Sound Labs, Maggies, and Newforms - the Sound Labs by virtue of their large, curved diaphragm which radiates over a constant 90-degree arc front and back, and the two ribbon speakers by virtue of their exceptionally narrow diaphragms.