While these two aren't too different, they do have different frequency response characteristics and presentation difference. The LS8 is warmer with more bass punch compared to a brighter sound with NT-6. Both have very airy sounds and give a complete, well rounded presentations but the NT-6 has a little more overall space and a better 3D space, although not nearly as large of a disparity as with the JH16. But, the NT-6 has better imaging, clarity, and transparency while detail levels, resolution, and speed are similar. The LS8 holds the edge in smoothness, with a more liquid presentation that is more forgiving compared with the more analytical NT-6.
With more bass and warmth, the LS8 is a capable performer, however the NT-6 bests the LS8 in reproducing sub-bass rumble and sounds just slightly more precise in direct comparison. Other than some minor quality differences, the bass quality is similar. The midrange is similar between these two except the NT-6 has better imaging by a bit along with the tonal differences of vocals due to the warmth differences. In the upper midrange the LS8 has a peak while the NT-6 has a bump, but much less prominent, and it carries over into the treble. The LS8 can have a tendency to accentuate the occasional sharp 'S' while this isn't an issue with the NT-6. The treble flip-flopped for me, with some tracks being more forgiving and liquid with the LS8 while other tracks that were mastered better sounded silky smooth with the NT-6, leaving the LS8 behind.
Both are good and perform at exceptional levels. The LS8 has a more forgiving and liquid presentation giving a more musical experience with a warmer and more bass centric sound. Conversely the NT-6 has a treble emphasis in comparison along with a more analytical sound. Technically the LS8 performs similarly in many ways, but the NT-6 is technically more competent with a superior overall soundstage recreation.
